mirror of
https://github.com/golang/go
synced 2024-10-02 22:25:08 +00:00
cmd/gc: correct handling of globals, func args, results
Globals, function arguments, and results are special cases in registerization. Globals must be flushed aggressively, because nearly any operation can cause a panic, and the recovery code must see the latest values. Globals also must be loaded aggressively, because nearly any store through a pointer might be updating a global: the compiler cannot see all the "address of" operations on globals, especially exported globals. To accomplish this, mark all globals as having their address taken, which effectively disables registerization. If a function contains a defer statement, the function results must be flushed aggressively, because nearly any operation can cause a panic, and the deferred code may call recover, causing the original function to return the current values of its function results. To accomplish this, mark all function results as having their address taken if the function contains any defer statements. This causes not just aggressive flushing but also aggressive loading. The aggressive loading is overkill but the best we can do in the current code. Function arguments must be considered live at all safe points in a function, because garbage collection always preserves them: they must be up-to-date in order to be preserved correctly. Accomplish this by marking them live at all call sites. An earlier attempt at this marked function arguments as having their address taken, which disabled registerization completely, making programs slower. This CL's solution allows registerization while preserving safety. The benchmark speedup is caused by being able to registerize again (the earlier CL lost the same amount). benchmark old ns/op new ns/op delta BenchmarkEqualPort32 61.4 56.0 -8.79% benchmark old MB/s new MB/s speedup BenchmarkEqualPort32 521.56 570.97 1.09x Fixes #1304. (again) Fixes #7944. (again) Fixes #7984. Fixes #7995. LGTM=khr R=golang-codereviews, khr CC=golang-codereviews, iant, r https://golang.org/cl/97500044
This commit is contained in:
parent
ec38c6f5e3
commit
f5184d3437
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@ -56,28 +56,6 @@ rcmp(const void *a1, const void *a2)
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return p2->varno - p1->varno;
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}
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static void
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setvar(Bits *dst, Type **args)
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{
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Type *t;
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Node *n;
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Addr a;
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Iter save;
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Bits bit;
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int z;
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t = structfirst(&save, args);
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while(t != T) {
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n = nodarg(t, 1);
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a = zprog.from;
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naddr(n, &a, 0);
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bit = mkvar(R, &a);
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for(z=0; z<BITS; z++)
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dst->b[z] |= bit.b[z];
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t = structnext(&save);
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}
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}
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void
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excise(Flow *r)
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{
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@ -192,11 +170,6 @@ regopt(Prog *firstp)
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ovar.b[z] = 0;
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}
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// build lists of parameters and results
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setvar(&ivar, getthis(curfn->type));
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setvar(&ivar, getinarg(curfn->type));
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setvar(&ovar, getoutarg(curfn->type));
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/*
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* pass 1
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* build aux data structure
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@ -837,9 +810,6 @@ mkvar(Reg *r, Adr *a)
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v->nextinnode = node->opt;
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node->opt = v;
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if(debug['R'])
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print("bit=%2d et=%2E w=%d+%d %#N %D flag=%d\n", i, et, o, w, node, a, v->addr);
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bit = blsh(i);
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if(n == D_EXTERN || n == D_STATIC)
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for(z=0; z<BITS; z++)
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@ -848,6 +818,13 @@ mkvar(Reg *r, Adr *a)
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for(z=0; z<BITS; z++)
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params.b[z] |= bit.b[z];
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if(node->class == PPARAM)
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for(z=0; z<BITS; z++)
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ivar.b[z] |= bit.b[z];
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if(node->class == PPARAMOUT)
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for(z=0; z<BITS; z++)
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ovar.b[z] |= bit.b[z];
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// Treat values with their address taken as live at calls,
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// because the garbage collector's liveness analysis in ../gc/plive.c does.
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// These must be consistent or else we will elide stores and the garbage
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@ -864,7 +841,21 @@ mkvar(Reg *r, Adr *a)
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// The broader := in a closure problem is mentioned in a comment in
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// closure.c:/^typecheckclosure and dcl.c:/^oldname.
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if(node->addrtaken)
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setaddrs(bit);
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v->addr = 1;
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// Disable registerization for globals, because:
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// (1) we might panic at any time and we want the recovery code
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// to see the latest values (issue 1304).
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// (2) we don't know what pointers might point at them and we want
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// loads via those pointers to see updated values and vice versa (issue 7995).
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//
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// Disable registerization for results if using defer, because the deferred func
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// might recover and return, causing the current values to be used.
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if(node->class == PEXTERN || (hasdefer && node->class == PPARAMOUT))
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v->addr = 1;
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if(debug['R'])
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print("bit=%2d et=%2E w=%d+%d %#N %D flag=%d\n", i, et, o, w, node, a, v->addr);
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return bit;
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@ -961,17 +952,6 @@ prop(Reg *r, Bits ref, Bits cal)
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ref.b[z] = 0;
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}
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break;
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default:
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// Work around for issue 1304:
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// flush modified globals before each instruction.
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for(z=0; z<BITS; z++) {
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cal.b[z] |= externs.b[z];
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// issue 4066: flush modified return variables in case of panic
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if(hasdefer)
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cal.b[z] |= ovar.b[z];
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}
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break;
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}
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for(z=0; z<BITS; z++) {
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ref.b[z] = (ref.b[z] & ~r1->set.b[z]) |
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@ -54,28 +54,6 @@ rcmp(const void *a1, const void *a2)
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return p2->varno - p1->varno;
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}
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static void
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setvar(Bits *dst, Type **args)
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{
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Type *t;
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Node *n;
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Addr a;
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Iter save;
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Bits bit;
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int z;
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t = structfirst(&save, args);
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while(t != T) {
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n = nodarg(t, 1);
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a = zprog.from;
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naddr(n, &a, 0);
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bit = mkvar(R, &a);
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for(z=0; z<BITS; z++)
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dst->b[z] |= bit.b[z];
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t = structnext(&save);
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}
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}
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static void
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setaddrs(Bits bit)
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{
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@ -178,11 +156,6 @@ regopt(Prog *firstp)
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ovar.b[z] = 0;
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}
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// build lists of parameters and results
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setvar(&ivar, getthis(curfn->type));
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setvar(&ivar, getinarg(curfn->type));
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setvar(&ovar, getoutarg(curfn->type));
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/*
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* pass 1
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* build aux data structure
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@ -690,11 +663,6 @@ mkvar(Reg *r, Adr *a)
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v->nextinnode = node->opt;
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node->opt = v;
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if(debug['R'])
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print("bit=%2d et=%2E w=%lld+%lld %#N %D flag=%d\n", i, et, o, w, node, a, v->addr);
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ostats.nvar++;
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bit = blsh(i);
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if(n == D_EXTERN || n == D_STATIC)
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for(z=0; z<BITS; z++)
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@ -703,6 +671,13 @@ mkvar(Reg *r, Adr *a)
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for(z=0; z<BITS; z++)
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params.b[z] |= bit.b[z];
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if(node->class == PPARAM)
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for(z=0; z<BITS; z++)
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ivar.b[z] |= bit.b[z];
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if(node->class == PPARAMOUT)
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for(z=0; z<BITS; z++)
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ovar.b[z] |= bit.b[z];
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// Treat values with their address taken as live at calls,
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// because the garbage collector's liveness analysis in ../gc/plive.c does.
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// These must be consistent or else we will elide stores and the garbage
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@ -719,7 +694,22 @@ mkvar(Reg *r, Adr *a)
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// The broader := in a closure problem is mentioned in a comment in
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// closure.c:/^typecheckclosure and dcl.c:/^oldname.
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if(node->addrtaken)
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setaddrs(bit);
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v->addr = 1;
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// Disable registerization for globals, because:
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// (1) we might panic at any time and we want the recovery code
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// to see the latest values (issue 1304).
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// (2) we don't know what pointers might point at them and we want
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// loads via those pointers to see updated values and vice versa (issue 7995).
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//
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// Disable registerization for results if using defer, because the deferred func
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// might recover and return, causing the current values to be used.
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if(node->class == PEXTERN || (hasdefer && node->class == PPARAMOUT))
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v->addr = 1;
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if(debug['R'])
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print("bit=%2d et=%2E w=%lld+%lld %#N %D flag=%d\n", i, et, o, w, node, a, v->addr);
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ostats.nvar++;
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return bit;
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@ -816,17 +806,6 @@ prop(Reg *r, Bits ref, Bits cal)
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ref.b[z] = 0;
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}
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break;
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default:
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// Work around for issue 1304:
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// flush modified globals before each instruction.
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for(z=0; z<BITS; z++) {
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cal.b[z] |= externs.b[z];
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// issue 4066: flush modified return variables in case of panic
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if(hasdefer)
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cal.b[z] |= ovar.b[z];
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}
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break;
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}
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for(z=0; z<BITS; z++) {
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ref.b[z] = (ref.b[z] & ~r1->set.b[z]) |
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@ -54,28 +54,6 @@ rcmp(const void *a1, const void *a2)
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return p2->varno - p1->varno;
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}
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static void
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setvar(Bits *dst, Type **args)
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{
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Type *t;
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Node *n;
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Addr a;
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Iter save;
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Bits bit;
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int z;
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t = structfirst(&save, args);
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while(t != T) {
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n = nodarg(t, 1);
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a = zprog.from;
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naddr(n, &a, 0);
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bit = mkvar(R, &a);
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for(z=0; z<BITS; z++)
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dst->b[z] |= bit.b[z];
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t = structnext(&save);
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}
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}
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static void
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setaddrs(Bits bit)
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{
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@ -148,11 +126,6 @@ regopt(Prog *firstp)
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ovar.b[z] = 0;
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}
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// build lists of parameters and results
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setvar(&ivar, getthis(curfn->type));
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setvar(&ivar, getinarg(curfn->type));
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setvar(&ovar, getoutarg(curfn->type));
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/*
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* pass 1
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* build aux data structure
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@ -656,10 +629,6 @@ mkvar(Reg *r, Adr *a)
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v->nextinnode = node->opt;
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node->opt = v;
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if(debug['R'])
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print("bit=%2d et=%2E w=%d+%d %#N %D flag=%d\n", i, et, o, w, node, a, v->addr);
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ostats.nvar++;
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bit = blsh(i);
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if(n == D_EXTERN || n == D_STATIC)
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for(z=0; z<BITS; z++)
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@ -667,6 +636,13 @@ mkvar(Reg *r, Adr *a)
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if(n == D_PARAM)
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for(z=0; z<BITS; z++)
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params.b[z] |= bit.b[z];
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if(node->class == PPARAM)
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for(z=0; z<BITS; z++)
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ivar.b[z] |= bit.b[z];
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if(node->class == PPARAMOUT)
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for(z=0; z<BITS; z++)
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ovar.b[z] |= bit.b[z];
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// Treat values with their address taken as live at calls,
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// because the garbage collector's liveness analysis in ../gc/plive.c does.
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@ -684,7 +660,22 @@ mkvar(Reg *r, Adr *a)
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// The broader := in a closure problem is mentioned in a comment in
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// closure.c:/^typecheckclosure and dcl.c:/^oldname.
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if(node->addrtaken)
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setaddrs(bit);
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v->addr = 1;
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|
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// Disable registerization for globals, because:
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// (1) we might panic at any time and we want the recovery code
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// to see the latest values (issue 1304).
|
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// (2) we don't know what pointers might point at them and we want
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// loads via those pointers to see updated values and vice versa (issue 7995).
|
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//
|
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// Disable registerization for results if using defer, because the deferred func
|
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// might recover and return, causing the current values to be used.
|
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if(node->class == PEXTERN || (hasdefer && node->class == PPARAMOUT))
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v->addr = 1;
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if(debug['R'])
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print("bit=%2d et=%2E w=%d+%d %#N %D flag=%d\n", i, et, o, w, node, a, v->addr);
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ostats.nvar++;
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return bit;
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@ -781,17 +772,6 @@ prop(Reg *r, Bits ref, Bits cal)
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ref.b[z] = 0;
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}
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break;
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default:
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// Work around for issue 1304:
|
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// flush modified globals before each instruction.
|
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for(z=0; z<BITS; z++) {
|
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cal.b[z] |= externs.b[z];
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// issue 4066: flush modified return variables in case of panic
|
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if(hasdefer)
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cal.b[z] |= ovar.b[z];
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}
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break;
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}
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for(z=0; z<BITS; z++) {
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ref.b[z] = (ref.b[z] & ~r1->set.b[z]) |
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|
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23
test/fixedbugs/issue1304.go
Normal file
23
test/fixedbugs/issue1304.go
Normal file
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@ -0,0 +1,23 @@
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// run
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// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
|
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// license that can be found in the LICENSE file.
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package main
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var a = 1
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func main() {
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defer func() {
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recover()
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if a != 2 {
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println("BUG a =", a)
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}
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}()
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a = 2
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b := a - a
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c := 4
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a = c / b
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a = 3
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}
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25
test/fixedbugs/issue7995.go
Normal file
25
test/fixedbugs/issue7995.go
Normal file
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@ -0,0 +1,25 @@
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// run
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// Copyright 2014 The Go Authors. All rights reserved.
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||||
// Use of this source code is governed by a BSD-style
|
||||
// license that can be found in the LICENSE file.
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||||
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// Issue 7995: globals not flushed quickly enough.
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package main
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import "fmt"
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var (
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p = 1
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q = &p
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)
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func main() {
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p = 50
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*q = 100
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s := fmt.Sprintln(p, *q)
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if s != "100 100\n" {
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println("BUG:", s)
|
||||
}
|
||||
}
|
16
test/fixedbugs/issue7995b.dir/x1.go
Normal file
16
test/fixedbugs/issue7995b.dir/x1.go
Normal file
|
@ -0,0 +1,16 @@
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|||
package x1
|
||||
|
||||
import "fmt"
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||||
|
||||
var P int
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|
||||
var b bool
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||||
|
||||
func F(x *int) string {
|
||||
if b { // avoid inlining
|
||||
F(x)
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||||
}
|
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P = 50
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*x = 100
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||||
return fmt.Sprintln(P, *x)
|
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}
|
10
test/fixedbugs/issue7995b.dir/x2.go
Normal file
10
test/fixedbugs/issue7995b.dir/x2.go
Normal file
|
@ -0,0 +1,10 @@
|
|||
package main
|
||||
|
||||
import "./x1"
|
||||
|
||||
func main() {
|
||||
s := x1.F(&x1.P)
|
||||
if s != "100 100\n" {
|
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println("BUG:", s)
|
||||
}
|
||||
}
|
9
test/fixedbugs/issue7995b.go
Normal file
9
test/fixedbugs/issue7995b.go
Normal file
|
@ -0,0 +1,9 @@
|
|||
// rundir
|
||||
|
||||
// Copyright 2014 The Go Authors. All rights reserved.
|
||||
// Use of this source code is governed by a BSD-style
|
||||
// license that can be found in the LICENSE file.
|
||||
|
||||
// Issue 7995: globals not flushed quickly enough.
|
||||
|
||||
package ignored
|
104
test/nilptr3.go
104
test/nilptr3.go
|
@ -17,7 +17,7 @@ type Struct struct {
|
|||
type BigStruct struct {
|
||||
X int
|
||||
Y float64
|
||||
A [1<<20]int
|
||||
A [1 << 20]int
|
||||
Z string
|
||||
}
|
||||
|
||||
|
@ -29,93 +29,94 @@ type Empty1 struct {
|
|||
}
|
||||
|
||||
var (
|
||||
intp *int
|
||||
arrayp *[10]int
|
||||
array0p *[0]int
|
||||
bigarrayp *[1<<26]int
|
||||
structp *Struct
|
||||
intp *int
|
||||
arrayp *[10]int
|
||||
array0p *[0]int
|
||||
bigarrayp *[1 << 26]int
|
||||
structp *Struct
|
||||
bigstructp *BigStruct
|
||||
emptyp *Empty
|
||||
empty1p *Empty1
|
||||
emptyp *Empty
|
||||
empty1p *Empty1
|
||||
)
|
||||
|
||||
func f1() {
|
||||
_ = *intp // ERROR "generated nil check"
|
||||
|
||||
|
||||
// This one should be removed but the block copy needs
|
||||
// to be turned into its own pseudo-op in order to see
|
||||
// the indirect.
|
||||
_ = *arrayp // ERROR "generated nil check"
|
||||
|
||||
// 0-byte indirect doesn't suffice
|
||||
_ = *array0p // ERROR "generated nil check"
|
||||
_ = *array0p // ERROR "removed repeated nil check" 386
|
||||
|
||||
_ = *intp // ERROR "removed repeated nil check"
|
||||
_ = *arrayp // ERROR "removed repeated nil check"
|
||||
// 0-byte indirect doesn't suffice.
|
||||
// we don't registerize globals, so there are no removed repeated nil checks.
|
||||
_ = *array0p // ERROR "generated nil check"
|
||||
_ = *array0p // ERROR "generated nil check"
|
||||
|
||||
_ = *intp // ERROR "generated nil check"
|
||||
_ = *arrayp // ERROR "generated nil check"
|
||||
_ = *structp // ERROR "generated nil check"
|
||||
_ = *emptyp // ERROR "generated nil check"
|
||||
_ = *arrayp // ERROR "removed repeated nil check"
|
||||
_ = *emptyp // ERROR "generated nil check"
|
||||
_ = *arrayp // ERROR "generated nil check"
|
||||
}
|
||||
|
||||
func f2() {
|
||||
var (
|
||||
intp *int
|
||||
arrayp *[10]int
|
||||
array0p *[0]int
|
||||
bigarrayp *[1<<20]int
|
||||
structp *Struct
|
||||
intp *int
|
||||
arrayp *[10]int
|
||||
array0p *[0]int
|
||||
bigarrayp *[1 << 20]int
|
||||
structp *Struct
|
||||
bigstructp *BigStruct
|
||||
emptyp *Empty
|
||||
empty1p *Empty1
|
||||
emptyp *Empty
|
||||
empty1p *Empty1
|
||||
)
|
||||
|
||||
_ = *intp // ERROR "generated nil check"
|
||||
_ = *arrayp // ERROR "generated nil check"
|
||||
_ = *array0p // ERROR "generated nil check"
|
||||
_ = *array0p // ERROR "removed repeated nil check"
|
||||
_ = *intp // ERROR "removed repeated nil check"
|
||||
_ = *arrayp // ERROR "removed repeated nil check"
|
||||
_ = *structp // ERROR "generated nil check"
|
||||
_ = *emptyp // ERROR "generated nil check"
|
||||
_ = *arrayp // ERROR "removed repeated nil check"
|
||||
_ = *bigarrayp // ERROR "generated nil check" ARM removed nil check before indirect!!
|
||||
_ = *intp // ERROR "generated nil check"
|
||||
_ = *arrayp // ERROR "generated nil check"
|
||||
_ = *array0p // ERROR "generated nil check"
|
||||
_ = *array0p // ERROR "removed repeated nil check"
|
||||
_ = *intp // ERROR "removed repeated nil check"
|
||||
_ = *arrayp // ERROR "removed repeated nil check"
|
||||
_ = *structp // ERROR "generated nil check"
|
||||
_ = *emptyp // ERROR "generated nil check"
|
||||
_ = *arrayp // ERROR "removed repeated nil check"
|
||||
_ = *bigarrayp // ERROR "generated nil check" ARM removed nil check before indirect!!
|
||||
_ = *bigstructp // ERROR "generated nil check"
|
||||
_ = *empty1p // ERROR "generated nil check"
|
||||
_ = *empty1p // ERROR "generated nil check"
|
||||
}
|
||||
|
||||
func fx10k() *[10000]int
|
||||
var b bool
|
||||
|
||||
var b bool
|
||||
|
||||
func f3(x *[10000]int) {
|
||||
// Using a huge type and huge offsets so the compiler
|
||||
// does not expect the memory hardware to fault.
|
||||
_ = x[9999] // ERROR "generated nil check"
|
||||
|
||||
|
||||
for {
|
||||
if x[9999] != 0 { // ERROR "generated nil check"
|
||||
break
|
||||
}
|
||||
}
|
||||
|
||||
x = fx10k()
|
||||
|
||||
x = fx10k()
|
||||
_ = x[9999] // ERROR "generated nil check"
|
||||
if b {
|
||||
_ = x[9999] // ERROR "removed repeated nil check"
|
||||
} else {
|
||||
_ = x[9999] // ERROR "removed repeated nil check"
|
||||
}
|
||||
}
|
||||
_ = x[9999] // ERROR "generated nil check"
|
||||
|
||||
x = fx10k()
|
||||
x = fx10k()
|
||||
if b {
|
||||
_ = x[9999] // ERROR "generated nil check"
|
||||
} else {
|
||||
_ = x[9999] // ERROR "generated nil check"
|
||||
}
|
||||
}
|
||||
_ = x[9999] // ERROR "generated nil check"
|
||||
|
||||
|
||||
fx10k()
|
||||
// This one is a bit redundant, if we figured out that
|
||||
// x wasn't going to change across the function call.
|
||||
|
@ -145,7 +146,7 @@ func f3b() {
|
|||
_ = &x[9] // ERROR "removed repeated nil check"
|
||||
}
|
||||
|
||||
func fx10() *[10]int
|
||||
func fx10() *[10]int
|
||||
|
||||
func f4(x *[10]int) {
|
||||
// Most of these have no checks because a real memory reference follows,
|
||||
|
@ -153,14 +154,14 @@ func f4(x *[10]int) {
|
|||
// in the first unmapped page of memory.
|
||||
|
||||
_ = x[9] // ERROR "removed nil check before indirect"
|
||||
|
||||
|
||||
for {
|
||||
if x[9] != 0 { // ERROR "removed nil check before indirect"
|
||||
break
|
||||
}
|
||||
}
|
||||
|
||||
x = fx10()
|
||||
|
||||
x = fx10()
|
||||
_ = x[9] // ERROR "removed nil check before indirect"
|
||||
if b {
|
||||
_ = x[9] // ERROR "removed nil check before indirect"
|
||||
|
@ -169,17 +170,17 @@ func f4(x *[10]int) {
|
|||
}
|
||||
_ = x[9] // ERROR "removed nil check before indirect"
|
||||
|
||||
x = fx10()
|
||||
x = fx10()
|
||||
if b {
|
||||
_ = x[9] // ERROR "removed nil check before indirect"
|
||||
} else {
|
||||
_ = &x[9] // ERROR "generated nil check"
|
||||
}
|
||||
}
|
||||
_ = x[9] // ERROR "removed nil check before indirect"
|
||||
|
||||
|
||||
fx10()
|
||||
_ = x[9] // ERROR "removed nil check before indirect"
|
||||
|
||||
|
||||
x = fx10()
|
||||
y := fx10()
|
||||
_ = &x[9] // ERROR "generated nil check"
|
||||
|
@ -188,4 +189,3 @@ func f4(x *[10]int) {
|
|||
x = y
|
||||
_ = &x[9] // ERROR "removed repeated nil check"
|
||||
}
|
||||
|
||||
|
|
Loading…
Reference in a new issue