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Fix a stackmap bug introduced in r220710.

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For a call to not return in to the stackmap shadow, the shadow must end with the call.

To do this, we must insert any required nops *before* the call, and not after it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220728 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Pete Cooper 2014-10-27 22:38:45 +00:00
parent cf84852133
commit 68aeef61f4
2 changed files with 21 additions and 6 deletions
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18
lib/Target/X86/X86MCInstLower.cpp
View File

@ -1209,11 +1209,21 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
MCInst TmpInst;
MCInstLowering.Lower(MI, TmpInst);
EmitAndCountInstruction(TmpInst);
// Stackmap shadows cannot include branch targets, so we can count the bytes
// in a call towards the shadow, but must flush the shadow immediately after
// to account for the return from the call.
if (MI->isCall())
// in a call towards the shadow, but must ensure that the no thread returns
// in to the stackmap shadow. The only way to achieve this is if the call
// is at the end of the shadow.
if (MI->isCall()) {
// Count then size of the call towards the shadow
SMShadowTracker.count(TmpInst, getSubtargetInfo());
// Then flush the shadow so that we fill with nops before the call, not
// after it.
SMShadowTracker.emitShadowPadding(OutStreamer, getSubtargetInfo());
// Then emit the call
OutStreamer.EmitInstruction(TmpInst, getSubtargetInfo());
return;
}
EmitAndCountInstruction(TmpInst);
}

9
test/CodeGen/X86/stackmap-shadow-optimization.ll
View File

@ -5,17 +5,22 @@
; bar. However, the frame teardown and the return do not count towards the
; stackmap shadow as the call return counts as a branch target so must flush
; the shadow.
; Note that in order for a thread to not return in to the patched space
; the call must be at the end of the shadow, so the required nop must be
; before the call, not after.
define void @shadow_optimization_test() {
entry:
; CHECK-LABEL: shadow_optimization_test:
; CHECK: callq _bar
; CHECK: nop
; CHECK: callq _bar
; CHECK-NOT: nop
; CHECK: callq _bar
; CHECK: nop
; CHECK: retq
; CHECK-NOT: nop
call void @bar()
tail call void (i64, i32, ...)* @llvm.experimental.stackmap(i64 0, i32 8)
call void @bar()
call void @bar()
ret void
}