[llvm] 8942d30 - [AArch64][WinCFI] Handle cases where no SEH opcodes in the prologue
Hiroshi Yamauchi via llvm-commits
llvm-commits at lists.llvm.org
Thu Aug 31 12:43:35 PDT 2023
Author: Hiroshi Yamauchi
Date: 2023-08-31T12:43:26-07:00
New Revision: 8942d3047c684af800da7c75566210725f1cfe84
URL: https://github.com/llvm/llvm-project/commit/8942d3047c684af800da7c75566210725f1cfe84
DIFF: https://github.com/llvm/llvm-project/commit/8942d3047c684af800da7c75566210725f1cfe84.diff
LOG: [AArch64][WinCFI] Handle cases where no SEH opcodes in the prologue
but there are some in the epilogue.
Make a decision whether or not to have a startepilogue/endepilogue
based on whether we actually insert SEH opcodes in the epilogue,
rather than whether we had SEH opcodes in the prologue or not.
This fixes an assert failure when there are no SEH opcodes in the
prologue but there are SEH opcodes in the epilogue (for example, when
there is no stack frame but there are stack arguments) which was not
covered in https://reviews.llvm.org/D88641.
Assertion failed: HasWinCFI == MF.hasWinCFI(), file C:\Users\hiroshi\llvm-project\llvm\lib\Target\AArch64\AArch64FrameLowering.cpp, line 1988
Differential Revision: https://reviews.llvm.org/D159238
Added:
llvm/test/CodeGen/AArch64/wincfi-seh-only-in-epilogue.ll
Modified:
llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index fd8694563add3b..a45b509fcb4a3b 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -1985,13 +1985,14 @@ void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
bool EmitCFI = AFI->needsAsyncDwarfUnwindInfo(MF);
bool HasWinCFI = false;
bool IsFunclet = false;
- auto WinCFI = make_scope_exit([&]() { assert(HasWinCFI == MF.hasWinCFI()); });
if (MBB.end() != MBBI) {
DL = MBBI->getDebugLoc();
IsFunclet = isFuncletReturnInstr(*MBBI);
}
+ MachineBasicBlock::iterator EpilogStartI = MBB.end();
+
auto FinishingTouches = make_scope_exit([&]() {
if (AFI->shouldSignReturnAddress(MF))
authenticateLR(MF, MBB, NeedsWinCFI, &HasWinCFI);
@@ -1999,10 +2000,18 @@ void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
emitShadowCallStackEpilogue(*TII, MF, MBB, MBB.getFirstTerminator(), DL);
if (EmitCFI)
emitCalleeSavedGPRRestores(MBB, MBB.getFirstTerminator());
- if (HasWinCFI)
+ if (HasWinCFI) {
BuildMI(MBB, MBB.getFirstTerminator(), DL,
TII->get(AArch64::SEH_EpilogEnd))
.setMIFlag(MachineInstr::FrameDestroy);
+ if (!MF.hasWinCFI())
+ MF.setHasWinCFI(true);
+ }
+ if (NeedsWinCFI) {
+ assert(EpilogStartI != MBB.end());
+ if (!HasWinCFI)
+ MBB.erase(EpilogStartI);
+ }
});
int64_t NumBytes = IsFunclet ? getWinEHFuncletFrameSize(MF)
@@ -2040,7 +2049,7 @@ void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
// Adjust local stack
emitFrameOffset(MBB, LastPopI, DL, AArch64::SP, AArch64::SP,
StackOffset::getFixed(AFI->getLocalStackSize()), TII,
- MachineInstr::FrameDestroy, false, NeedsWinCFI);
+ MachineInstr::FrameDestroy, false, NeedsWinCFI, &HasWinCFI);
// SP has been already adjusted while restoring callee save regs.
// We've bailed-out the case with adjusting SP for arguments.
@@ -2092,16 +2101,17 @@ void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
NeedsWinCFI, &HasWinCFI);
}
- if (MF.hasWinCFI()) {
- // If the prologue didn't contain any SEH opcodes and didn't set the
- // MF.hasWinCFI() flag, assume the epilogue won't either, and skip the
- // EpilogStart - to avoid generating CFI for functions that don't need it.
- // (And as we didn't generate any prologue at all, it would be asymmetrical
- // to the epilogue.) By the end of the function, we assert that
- // HasWinCFI is equal to MF.hasWinCFI(), to verify this assumption.
- HasWinCFI = true;
+ if (NeedsWinCFI) {
+ // Note that there are cases where we insert SEH opcodes in the
+ // epilogue when we had no SEH opcodes in the prologue. For
+ // example, when there is no stack frame but there are stack
+ // arguments. Insert the SEH_EpilogStart and remove it later if it
+ // we didn't emit any SEH opcodes to avoid generating WinCFI for
+ // functions that don't need it.
BuildMI(MBB, LastPopI, DL, TII->get(AArch64::SEH_EpilogStart))
.setMIFlag(MachineInstr::FrameDestroy);
+ EpilogStartI = LastPopI;
+ --EpilogStartI;
}
if (hasFP(MF) && AFI->hasSwiftAsyncContext()) {
@@ -2255,11 +2265,11 @@ void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
emitFrameOffset(
MBB, LastPopI, DL, AArch64::SP, AArch64::FP,
StackOffset::getFixed(-AFI->getCalleeSaveBaseToFrameRecordOffset()),
- TII, MachineInstr::FrameDestroy, false, NeedsWinCFI);
+ TII, MachineInstr::FrameDestroy, false, NeedsWinCFI, &HasWinCFI);
} else if (NumBytes)
emitFrameOffset(MBB, LastPopI, DL, AArch64::SP, AArch64::SP,
StackOffset::getFixed(NumBytes), TII,
- MachineInstr::FrameDestroy, false, NeedsWinCFI);
+ MachineInstr::FrameDestroy, false, NeedsWinCFI, &HasWinCFI);
// When we are about to restore the CSRs, the CFA register is SP again.
if (EmitCFI && hasFP(MF)) {
diff --git a/llvm/test/CodeGen/AArch64/wincfi-seh-only-in-epilogue.ll b/llvm/test/CodeGen/AArch64/wincfi-seh-only-in-epilogue.ll
new file mode 100644
index 00000000000000..7daceae3dd4c03
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/wincfi-seh-only-in-epilogue.ll
@@ -0,0 +1,13 @@
+; RUN: llc -mtriple=aarch64-windows %s -o - | FileCheck %s
+
+define hidden swifttailcc void @test(ptr noalias nocapture %0, ptr swiftasync %1, ptr %2, ptr noalias nocapture %3, ptr nocapture dereferenceable(8) %4, ptr %5, ptr %6, ptr %Act, ptr %Err, ptr %Res, ptr %Act.DistributedActor, ptr %Err.Error, ptr %Res.Decodable, ptr %Res.Encodable, ptr swiftself %7) #0 {
+entry:
+ ret void
+}
+
+; Check that there is no .seh_endprologue but there is seh_startepilogue/seh_endepilogue.
+; CHECK-NOT: .seh_endprologue
+; CHECK: .seh_startepilogue
+; CHECK: add sp, sp, #48
+; CHECK: .seh_stackalloc 48
+; CHECK: .seh_endepilogue
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