Author: Reid Kleckner Date: 2021-01-25T10:39:27-08:00 New Revision: 988a5334ed40ee65c91bf30be93631b092316390
URL: https://github.com/llvm/llvm-project/commit/988a5334ed40ee65c91bf30be93631b092316390 DIFF: https://github.com/llvm/llvm-project/commit/988a5334ed40ee65c91bf30be93631b092316390.diff LOG: [Win64] Ensure all stack frames are 8 byte aligned The unwind info format requires that all adjustments are 8 byte aligned, and the bottom three bits are masked out. Most Win64 calling conventions have 32 bytes of shadow stack space for spilling parameters, and I believe that constructing these fixed stack objects had the side effect of ensuring an alignment of 8. However, the Intel regcall convention does not have this shadow space, so when using that convention, it was possible to make a 4 byte stack frame, which was impossible to describe with unwind info. Fixes pr48867 Added: llvm/test/CodeGen/X86/win64_regcall.ll Modified: llvm/lib/Target/X86/X86FrameLowering.cpp llvm/lib/Target/X86/X86FrameLowering.h Removed: ################################################################################ diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp index 8339f512158d..866f11364004 100644 --- a/llvm/lib/Target/X86/X86FrameLowering.cpp +++ b/llvm/lib/Target/X86/X86FrameLowering.cpp @@ -3516,13 +3516,21 @@ void X86FrameLowering::processFunctionBeforeFrameFinalized( // emitPrologue if it gets called and emits CFI. MF.setHasWinCFI(false); + // If we are using Windows x64 CFI, ensure that the stack is always 8 byte + // aligned. The format doesn't support misaligned stack adjustments. + if (MF.getTarget().getMCAsmInfo()->usesWindowsCFI()) + MF.getFrameInfo().ensureMaxAlignment(Align(SlotSize)); + // If this function isn't doing Win64-style C++ EH, we don't need to do // anything. - const Function &F = MF.getFunction(); - if (!STI.is64Bit() || !MF.hasEHFunclets() || - classifyEHPersonality(F.getPersonalityFn()) != EHPersonality::MSVC_CXX) - return; + if (STI.is64Bit() && MF.hasEHFunclets() && + classifyEHPersonality(MF.getFunction().getPersonalityFn()) == + EHPersonality::MSVC_CXX) { + adjustFrameForMsvcCxxEh(MF); + } +} +void X86FrameLowering::adjustFrameForMsvcCxxEh(MachineFunction &MF) const { // Win64 C++ EH needs to allocate the UnwindHelp object at some fixed offset // relative to RSP after the prologue. Find the offset of the last fixed // object, so that we can allocate a slot immediately following it. If there diff --git a/llvm/lib/Target/X86/X86FrameLowering.h b/llvm/lib/Target/X86/X86FrameLowering.h index f77a4843bba4..26e80811af2e 100644 --- a/llvm/lib/Target/X86/X86FrameLowering.h +++ b/llvm/lib/Target/X86/X86FrameLowering.h @@ -224,6 +224,8 @@ class X86FrameLowering : public TargetFrameLowering { const DebugLoc &DL, uint64_t Offset, uint64_t Align) const; + void adjustFrameForMsvcCxxEh(MachineFunction &MF) const; + /// Aligns the stack pointer by ANDing it with -MaxAlign. void BuildStackAlignAND(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI, const DebugLoc &DL, diff --git a/llvm/test/CodeGen/X86/win64_regcall.ll b/llvm/test/CodeGen/X86/win64_regcall.ll new file mode 100644 index 000000000000..4cd051928f36 --- /dev/null +++ b/llvm/test/CodeGen/X86/win64_regcall.ll @@ -0,0 +1,12 @@ +; RUN: llc < %s -mtriple=x86_64-windows-msvc | FileCheck %s + +define dso_local x86_regcallcc void @ensure_align() local_unnamed_addr #0 { +entry: + %b = alloca i32, align 4 + call void asm sideeffect "nopl $0", "=*m,~{dirflag},~{fpsr},~{flags}"(i32* nonnull %b) + ret void +} + +; CHECK-LABEL: ensure_align: # @ensure_align +; CHECK: .seh_stackalloc 8 +; CHECK: .seh_endprologue _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
