[llvm] r214775 - Fix failure to invoke exception handler on Win64
Reid Kleckner
reid at kleckner.net
Mon Aug 4 14:05:28 PDT 2014
Author: rnk
Date: Mon Aug 4 16:05:27 2014
New Revision: 214775
URL: http://llvm.org/viewvc/llvm-project?rev=214775&view=rev
Log:
Fix failure to invoke exception handler on Win64
When the last instruction prior to a function epilogue is a call, we
need to emit a nop so that the return address is not in the epilogue IP
range. This is consistent with MSVC's behavior, and may be a workaround
for a bug in the Win64 unwinder.
Differential Revision: http://reviews.llvm.org/D4751
Patch by Vadim Chugunov!
Added:
llvm/trunk/test/CodeGen/X86/win64_call_epi.ll
Modified:
llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
llvm/trunk/lib/Target/X86/X86InstrCompiler.td
llvm/trunk/lib/Target/X86/X86MCInstLower.cpp
Modified: llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FrameLowering.cpp?rev=214775&r1=214774&r2=214775&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86FrameLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86FrameLowering.cpp Mon Aug 4 16:05:27 2014
@@ -849,6 +849,11 @@ void X86FrameLowering::emitEpilogue(Mach
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");
@@ -933,17 +938,29 @@ void X86FrameLowering::emitEpilogue(Mach
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.
if (RetOpcode == X86::EH_RETURN || RetOpcode == X86::EH_RETURN64) {
MBBI = MBB.getLastNonDebugInstr();
Modified: llvm/trunk/lib/Target/X86/X86InstrCompiler.td
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrCompiler.td?rev=214775&r1=214774&r2=214775&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrCompiler.td (original)
+++ llvm/trunk/lib/Target/X86/X86InstrCompiler.td Mon Aug 4 16:05:27 2014
@@ -214,6 +214,8 @@ let isPseudo = 1 in {
"#SEH_PushFrame $mode", []>;
def SEH_EndPrologue : I<0, Pseudo, (outs), (ins),
"#SEH_EndPrologue", []>;
+ def SEH_Epilogue : I<0, Pseudo, (outs), (ins),
+ "#SEH_Epilogue", []>;
}
//===----------------------------------------------------------------------===//
Modified: llvm/trunk/lib/Target/X86/X86MCInstLower.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86MCInstLower.cpp?rev=214775&r1=214774&r2=214775&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86MCInstLower.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86MCInstLower.cpp Mon Aug 4 16:05:27 2014
@@ -826,6 +826,20 @@ void X86AsmPrinter::LowerPATCHPOINT(cons
getSubtargetInfo());
}
+// Returns instruction preceding MBBI in MachineFunction.
+// If MBBI is the first instruction of the first basic block, returns null.
+static MachineBasicBlock::const_iterator
+PrevCrossBBInst(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 =
@@ -967,6 +981,21 @@ void X86AsmPrinter::EmitInstruction(cons
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 = PrevCrossBBInst(MBBI); MBBI; MBBI = PrevCrossBBInst(MBBI)) {
+ // Conservatively assume that pseudo instructions don't emit code and keep
+ // looking for a call. We may emit an unnecessary nop in some cases.
+ if (!MBBI->isPseudo()) {
+ if (MBBI->isCall())
+ EmitAndCountInstruction(MCInstBuilder(X86::NOOP));
+ break;
+ }
+ }
+ return;
+ }
+
case X86::PSHUFBrm:
case X86::VPSHUFBrm:
// Lower PSHUFB normally but add a comment if we can find a constant
Added: llvm/trunk/test/CodeGen/X86/win64_call_epi.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/win64_call_epi.ll?rev=214775&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/win64_call_epi.ll (added)
+++ llvm/trunk/test/CodeGen/X86/win64_call_epi.ll Mon Aug 4 16:05:27 2014
@@ -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.
+ at 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
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