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cmd/5a, cmd/dist, runtime: support m/g in the assembler, drop support for R9/R10

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to avoid unintentionally clobber R9/R10.
Thanks Lucio for the suggestion.

PS: yes, this could be considered a big change (but not an API change), but
as it turns out even temporarily changes R9/R10 in user code is unsafe and
leads to very hard to diagnose problems later, better to disable using R9/R10
when the user first uses it.
See CL 6300043 and CL 6305100 for two problems caused by misusing R9/R10.

R=golang-dev, khr, rsc
CC=golang-dev
https://golang.org/cl/9840043
This commit is contained in:
Shenghou Ma 2013-05-30 03:03:52 +08:00
parent a307c5c9b7
commit 5d081792b6
5 changed files with 28 additions and 28 deletions
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2
doc/go1.2.txt
View file

@ -8,5 +8,7 @@ Please keep the descriptions to a single line, starting with the
package or cmd/xxx directory name, and ending in a CL number.
Please keep the list sorted (as in sort.Strings of the lines).
cmd/5a: removed support for R9/R10 (use m/g instead) (CL 9840043).
fmt: indexed access to arguments in Printf etc. (CL 9680043).
io: Copy prioritizes WriterTo over ReaderFrom (CL 9462044).

4
src/cmd/5a/lex.c
View file

@ -191,8 +191,8 @@ struct
"R6", LREG, 6,
"R7", LREG, 7,
"R8", LREG, 8,
"R9", LREG, 9,
"R10", LREG, 10,
"m", LREG, 9, // avoid unintentionally clobber m/g using R9/R10
"g", LREG, 10,
"R11", LREG, 11,
"R12", LREG, 12,
"R13", LREG, 13,

2
src/cmd/dist/buildruntime.c vendored
View file

@ -174,8 +174,6 @@ static struct {
},
{"arm", "",
"#define g R10\n"
"#define m R9\n"
"#define LR R14\n"
},
};

4
src/pkg/runtime/cgo/asm_arm.s
View file

@ -15,9 +15,9 @@ TEXT crosscall2(SB),7,$-4
* Additionally, cgo_tls_set_gm will clobber R0, so we need to save R0
* nevertheless.
*/
MOVM.WP [R0, R1, R2, R4, R5, R6, R7, R8, R9, R10, R11, R12, R14], (R13)
MOVM.WP [R0, R1, R2, R4, R5, R6, R7, R8, m, g, R11, R12, R14], (R13)
MOVW _cgo_load_gm(SB), R0
BL (R0)
MOVW PC, R14
MOVW 0(R13), PC
MOVM.IAW (R13), [R0, R1, R2, R4, R5, R6, R7, R8, R9, R10, R11, R12, PC]
MOVM.IAW (R13), [R0, R1, R2, R4, R5, R6, R7, R8, m, g, R11, R12, PC]

44
src/pkg/runtime/vlop_arm.s
View file

@ -70,7 +70,7 @@ TEXT _sfloat(SB), 7, $64 // 4 arg + 14*4 saved regs + cpsr
q = 0 // input d, output q
r = 1 // input n, output r
s = 2 // three temporary variables
m = 3
M = 3
a = 11
// Please be careful when changing this, it is pretty fragile:
// 1, don't use unconditional branch as the linker is free to reorder the blocks;
@ -83,31 +83,31 @@ TEXT udiv<>(SB),7,$-4
begin:
SUB.S $7, R(s)
RSB $0, R(q), R(m) // m = -q
RSB $0, R(q), R(M) // M = -q
MOVW.PL R(a)<<R(s), R(q)
// 1st Newton iteration
MUL.PL R(m), R(q), R(a) // a = -q*d
MUL.PL R(M), R(q), R(a) // a = -q*d
BMI udiv_by_large_d
MULAWT R(a), R(q), R(q), R(q) // q approx q-(q*q*d>>32)
TEQ R(m)->1, R(m) // check for d=0 or d=1
TEQ R(M)->1, R(M) // check for d=0 or d=1
// 2nd Newton iteration
MUL.NE R(m), R(q), R(a)
MUL.NE R(M), R(q), R(a)
MOVW.NE $0, R(s)
MULAL.NE R(q), R(a), (R(q),R(s))
BEQ udiv_by_0_or_1
// q now accurate enough for a remainder r, 0<=r<3*d
MULLU R(q), R(r), (R(q),R(s)) // q = (r * q) >> 32
ADD R(m), R(r), R(r) // r = n - d
MULA R(m), R(q), R(r), R(r) // r = n - (q+1)*d
ADD R(M), R(r), R(r) // r = n - d
MULA R(M), R(q), R(r), R(r) // r = n - (q+1)*d
// since 0 <= n-q*d < 3*d; thus -d <= r < 2*d
CMN R(m), R(r) // t = r-d
SUB.CS R(m), R(r), R(r) // if (t<-d || t>=0) r=r+d
CMN R(M), R(r) // t = r-d
SUB.CS R(M), R(r), R(r) // if (t<-d || t>=0) r=r+d
ADD.CC $1, R(q)
ADD.PL R(m)<<1, R(r)
ADD.PL R(M)<<1, R(r)
ADD.PL $2, R(q)
// return, can't use RET here or fast_udiv_tab will be dropped during linking
@ -119,14 +119,14 @@ udiv_by_large_d:
RSB $0, R(s), R(s)
MOVW R(a)>>R(s), R(q)
MULLU R(q), R(r), (R(q),R(s))
MULA R(m), R(q), R(r), R(r)
MULA R(M), R(q), R(r), R(r)
// q now accurate enough for a remainder r, 0<=r<4*d
CMN R(r)>>1, R(m) // if(r/2 >= d)
ADD.CS R(m)<<1, R(r)
CMN R(r)>>1, R(M) // if(r/2 >= d)
ADD.CS R(M)<<1, R(r)
ADD.CS $2, R(q)
CMN R(r), R(m)
ADD.CS R(m), R(r)
CMN R(r), R(M)
ADD.CS R(M), R(r)
ADD.CS $1, R(q)
// return, can't use RET here or fast_udiv_tab will be dropped during linking
@ -170,7 +170,7 @@ TEXT _divu(SB), 7, $16
MOVW R(q), 4(R13)
MOVW R(r), 8(R13)
MOVW R(s), 12(R13)
MOVW R(m), 16(R13)
MOVW R(M), 16(R13)
MOVW R(TMP), R(r) /* numerator */
MOVW 0(FP), R(q) /* denominator */
@ -179,14 +179,14 @@ TEXT _divu(SB), 7, $16
MOVW 4(R13), R(q)
MOVW 8(R13), R(r)
MOVW 12(R13), R(s)
MOVW 16(R13), R(m)
MOVW 16(R13), R(M)
RET
TEXT _modu(SB), 7, $16
MOVW R(q), 4(R13)
MOVW R(r), 8(R13)
MOVW R(s), 12(R13)
MOVW R(m), 16(R13)
MOVW R(M), 16(R13)
MOVW R(TMP), R(r) /* numerator */
MOVW 0(FP), R(q) /* denominator */
@ -195,14 +195,14 @@ TEXT _modu(SB), 7, $16
MOVW 4(R13), R(q)
MOVW 8(R13), R(r)
MOVW 12(R13), R(s)
MOVW 16(R13), R(m)
MOVW 16(R13), R(M)
RET
TEXT _div(SB),7,$16
MOVW R(q), 4(R13)
MOVW R(r), 8(R13)
MOVW R(s), 12(R13)
MOVW R(m), 16(R13)
MOVW R(M), 16(R13)
MOVW R(TMP), R(r) /* numerator */
MOVW 0(FP), R(q) /* denominator */
CMP $0, R(r)
@ -228,7 +228,7 @@ TEXT _mod(SB),7,$16
MOVW R(q), 4(R13)
MOVW R(r), 8(R13)
MOVW R(s), 12(R13)
MOVW R(m), 16(R13)
MOVW R(M), 16(R13)
MOVW R(TMP), R(r) /* numerator */
MOVW 0(FP), R(q) /* denominator */
CMP $0, R(q)
@ -246,5 +246,5 @@ out:
MOVW 4(R13), R(q)
MOVW 8(R13), R(r)
MOVW 12(R13), R(s)
MOVW 16(R13), R(m)
MOVW 16(R13), R(M)
RET