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[vm/ffi] Document shadow space and restore RSP

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Split off from https://dart-review.googlesource.com/c/sdk/+/140290.
We start using the stack after the C call, so RSP needs to be restored.

Issue https://github.com/dart-lang/sdk/issues/36730.

TEST=All existing FFI tests on windows.

Change-Id: Idcaff9007c1b6f42b95288e39470b3d6cca2ef56
Cq-Include-Trybots: luci.dart.try:vm-kernel-win-debug-x64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/170425
Reviewed-by: Martin Kustermann <kustermann@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>
This commit is contained in:
Daco Harkes 2020-11-05 13:58:43 +00:00 committed by commit-bot@chromium.org
parent b1946a51ed
commit 633c5389a5
5 changed files with 25 additions and 7 deletions
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12
runtime/vm/compiler/assembler/assembler_x64.cc
View file

@ -1671,19 +1671,27 @@ void Assembler::LeaveCallRuntimeFrame() {
LeaveStubFrame();
}
void Assembler::CallCFunction(Register reg) {
void Assembler::CallCFunction(Register reg, bool restore_rsp) {
// Reserve shadow space for outgoing arguments.
if (CallingConventions::kShadowSpaceBytes != 0) {
subq(RSP, Immediate(CallingConventions::kShadowSpaceBytes));
}
call(reg);
// Restore stack.
if (restore_rsp && CallingConventions::kShadowSpaceBytes != 0) {
addq(RSP, Immediate(CallingConventions::kShadowSpaceBytes));
}
}
void Assembler::CallCFunction(Address address) {
void Assembler::CallCFunction(Address address, bool restore_rsp) {
// Reserve shadow space for outgoing arguments.
if (CallingConventions::kShadowSpaceBytes != 0) {
subq(RSP, Immediate(CallingConventions::kShadowSpaceBytes));
}
call(address);
// Restore stack.
if (restore_rsp && CallingConventions::kShadowSpaceBytes != 0) {
addq(RSP, Immediate(CallingConventions::kShadowSpaceBytes));
}
}
void Assembler::CallRuntime(const RuntimeEntry& entry,

6
runtime/vm/compiler/assembler/assembler_x64.h
View file

@ -829,9 +829,9 @@ class Assembler : public AssemblerBase {
void CallRuntime(const RuntimeEntry& entry, intptr_t argument_count);
// Call runtime function. Reserves shadow space on the stack before calling
// if platform ABI requires that. Does not restore RSP after the call itself.
void CallCFunction(Register reg);
void CallCFunction(Address address);
// if platform ABI requires that.
void CallCFunction(Register reg, bool restore_rsp = false);
void CallCFunction(Address address, bool restore_rsp = false);
void ExtractClassIdFromTags(Register result, Register tags);
void ExtractInstanceSizeFromTags(Register result, Register tags);

2
runtime/vm/compiler/backend/il_x64.cc
View file

@ -1082,7 +1082,7 @@ void FfiCallInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
__ TransitionGeneratedToNative(target_address, FPREG, TMP,
/*enter_safepoint=*/true);
__ CallCFunction(target_address);
__ CallCFunction(target_address, /*restore_rsp=*/true);
// Update information in the thread object and leave the safepoint.
__ TransitionNativeToGenerated(/*leave_safepoint=*/true);

2
runtime/vm/compiler/stub_code_compiler_x64.cc
View file

@ -282,7 +282,7 @@ void StubCodeCompiler::GenerateCallNativeThroughSafepointStub(
/*enter_safepoint=*/true);
__ popq(R12);
__ CallCFunction(RBX);
__ CallCFunction(RBX, /*restore_rsp=*/true);
__ TransitionNativeToGenerated(/*leave_safepoint=*/true);

10
runtime/vm/constants_x64.h
View file

@ -304,6 +304,16 @@ class CallingConventions {
// same time? (Windows no, rest yes)
static const bool kArgumentIntRegXorFpuReg = true;
// > The x64 Application Binary Interface (ABI) uses a four-register
// > fast-call calling convention by default. Space is allocated on the call
// > stack as a shadow store for callees to save those registers.
// https://docs.microsoft.com/en-us/cpp/build/x64-calling-convention?view=msvc-160
//
// The caller allocates this space. The caller should also reclaim this space
// after the call to restore the stack to its original state if needed.
//
// This is also known as home space.
// https://devblogs.microsoft.com/oldnewthing/20160623-00/?p=93735
static const intptr_t kShadowSpaceBytes = 4 * kWordSize;
static const intptr_t kVolatileCpuRegisters =