Index: lib/Target/X86/X86FrameLowering.cpp =================================================================== --- lib/Target/X86/X86FrameLowering.cpp +++ lib/Target/X86/X86FrameLowering.cpp @@ -849,6 +849,11 @@ unsigned FramePtr = RegInfo->getFrameRegister(MF); unsigned StackPtr = RegInfo->getStackRegister(); + bool IsWinEH = + MF.getTarget().getMCAsmInfo()->getExceptionHandlingType() == + ExceptionHandling::WinEH; + bool NeedsWinEH = IsWinEH && MF.getFunction()->needsUnwindTableEntry(); + switch (RetOpcode) { default: llvm_unreachable("Can only insert epilog into returning blocks"); @@ -933,15 +938,28 @@ unsigned Opc = getLEArOpcode(IsLP64); addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr), FramePtr, false, -CSSize); + --MBBI; } else { unsigned Opc = (Is64Bit ? X86::MOV64rr : X86::MOV32rr); BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr) .addReg(FramePtr); + --MBBI; } } else if (NumBytes) { // Adjust stack pointer back: ESP += numbytes. emitSPUpdate(MBB, MBBI, StackPtr, NumBytes, Is64Bit, IsLP64, UseLEA, TII, *RegInfo); + --MBBI; + } + + // Windows unwinder will not invoke function's exception handler if IP + // is either in prologue or in epilogue. This behavior causes a problem + // when a call immediately precedes an epilogue, because the return + // address points into the epilogue. To cope with that, we insert + // an epilogue marker here, then replace it with a 'nop' if it ends up + // immediately after a CALL in the final emitted code. + if (NeedsWinEH) { + BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_Epilogue)); } // We're returning from function via eh_return. Index: lib/Target/X86/X86InstrCompiler.td =================================================================== --- lib/Target/X86/X86InstrCompiler.td +++ lib/Target/X86/X86InstrCompiler.td @@ -214,6 +214,8 @@ "#SEH_PushFrame $mode", []>; def SEH_EndPrologue : I<0, Pseudo, (outs), (ins), "#SEH_EndPrologue", []>; + def SEH_Epilogue : I<0, Pseudo, (outs), (ins), + "#SEH_Epilogue", []>; } //===----------------------------------------------------------------------===// Index: lib/Target/X86/X86MCInstLower.cpp =================================================================== --- lib/Target/X86/X86MCInstLower.cpp +++ lib/Target/X86/X86MCInstLower.cpp @@ -823,6 +823,21 @@ getSubtargetInfo()); } +// Returns instruction preceding MBBI in MachineFunction. +// If MBBI is the first instruction of the first basic block, returns null. +static MachineBasicBlock::const_iterator prev_inst( + MachineBasicBlock::const_iterator MBBI) { + + const MachineBasicBlock* MBB = MBBI->getParent(); + while (MBBI == MBB->begin()) { + if (MBB == MBB->getParent()->begin()) + return nullptr; + MBB = MBB->getPrevNode(); + MBBI = MBB->end(); + } + return --MBBI; +} + void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) { X86MCInstLower MCInstLowering(*MF, *this); const X86RegisterInfo *RI = @@ -963,6 +978,19 @@ case X86::SEH_EndPrologue: OutStreamer.EmitWinCFIEndProlog(); return; + + case X86::SEH_Epilogue: + MachineBasicBlock::const_iterator MBBI(MI); + // Check if preceded by a call and emit nop if so. + for (MBBI = prev_inst(MBBI); MBBI; MBBI = prev_inst(MBBI)) { + // Pseudo's aren't real instructions, so they don't count. + if (!MBBI->isPseudo()) { + if (MBBI->isCall()) + EmitAndCountInstruction(MCInstBuilder(X86::NOOP)); + break; + } + } + return; } MCInst TmpInst; Index: test/CodeGen/X86/win64_call_epi.ll =================================================================== --- /dev/null +++ test/CodeGen/X86/win64_call_epi.ll @@ -0,0 +1,65 @@ +; RUN: llc < %s -mtriple=x86_64-pc-mingw32 | FileCheck %s -check-prefix=WIN64 + +declare void @bar() +declare void @baz() +declare i32 @personality(...) + +; Check for 'nop' between the last call and the epilogue. +define void @foo1() { + + invoke void @bar() + to label %normal + unwind label %catch + +normal: + ret void + +catch: + %1 = landingpad { i8*, i32 } personality i32 (...)* @personality cleanup + resume { i8*, i32 } %1 +} +; WIN64-LABEL: foo1: +; WIN64: .seh_proc foo1 +; WIN64: callq bar +; WIN64: nop +; WIN64: addq ${{[0-9]+}}, %rsp +; WIN64: retq +; Check for 'ud2' after noreturn call +; WIN64: callq _Unwind_Resume +; WIN64-NEXT: ud2 +; WIN64: .seh_endproc + + +; Check it still works when blocks are reordered. +@something = global i32 0 +define void @foo2(i1 zeroext %cond ) { + br i1 %cond, label %a, label %b, !prof !0 +a: + call void @bar() + br label %done +b: + call void @baz() + store i32 0, i32* @something + br label %done +done: + ret void +} +!0 = metadata !{metadata !"branch_weights", i32 100, i32 0} +; WIN64-LABEL: foo2: +; WIN64: callq bar +; WIN64: nop +; WIN64: addq ${{[0-9]+}}, %rsp +; WIN64: retq + + +; Check nop is not emitted when call is not adjacent to epilogue. +define i32 @foo3() { + call void @bar() + ret i32 0 +} +; WIN64-LABEL: foo3: +; WIN64: callq bar +; WIN64: xorl +; WIN64-NOT: nop +; WIN64: addq ${{[0-9]+}}, %rsp +; WIN64: retq