Revert "Revert r248959, "[WinEH] Emit int3 after noreturn calls on Win64""

This reverts commit r249032.

TODO write commit msg

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249794 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetOptions.h

@@ -71,7 +71,7 @@ namespace llvm {
           EnableFastISel(false), PositionIndependentExecutable(false),
           UseInitArray(false), DisableIntegratedAS(false),
           CompressDebugSections(false), FunctionSections(false),
-          DataSections(false), UniqueSectionNames(true), TrapUnreachable(false),
+          DataSections(false), UniqueSectionNames(true),
           EmulatedTLS(false), FloatABIType(FloatABI::Default),
           AllowFPOpFusion(FPOpFusion::Standard), Reciprocals(TargetRecip()),
           JTType(JumpTable::Single),
@@ -169,9 +169,6 @@ namespace llvm {
 
     unsigned UniqueSectionNames : 1;
 
-    /// Emit target-specific trap instruction for 'unreachable' IR instructions.
-    unsigned TrapUnreachable : 1;
-
     /// EmulatedTLS - This flag enables emulated TLS model, using emutls
     /// function in the runtime library..
     unsigned EmulatedTLS : 1;
@@ -234,7 +231,6 @@ inline bool operator==(const TargetOptions &LHS,
     ARE_EQUAL(EnableFastISel) &&
     ARE_EQUAL(PositionIndependentExecutable) &&
     ARE_EQUAL(UseInitArray) &&
-    ARE_EQUAL(TrapUnreachable) &&
     ARE_EQUAL(EmulatedTLS) &&
     ARE_EQUAL(FloatABIType) &&
     ARE_EQUAL(AllowFPOpFusion) &&

lib/CodeGen/SelectionDAG/FastISel.cpp

@@ -1569,10 +1569,8 @@ bool FastISel::selectOperator(const User *I, unsigned Opcode) {
   }
 
   case Instruction::Unreachable:
-    if (TM.Options.TrapUnreachable)
+    // Nothing to emit.
-      return fastEmit_(MVT::Other, MVT::Other, ISD::TRAP) != 0;
+    return true;
-    else
-      return true;
 
   case Instruction::Alloca:
     // FunctionLowering has the static-sized case covered.

lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -2260,11 +2260,7 @@ void SelectionDAGBuilder::visitIndirectBr(const IndirectBrInst &I) {
                           getValue(I.getAddress())));
 }
 
-void SelectionDAGBuilder::visitUnreachable(const UnreachableInst &I) {
+void SelectionDAGBuilder::visitUnreachable(const UnreachableInst &I) {}
-  if (DAG.getTarget().Options.TrapUnreachable)
-    DAG.setRoot(
-        DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, DAG.getRoot()));
-}
 
 void SelectionDAGBuilder::visitFSub(const User &I) {
   // -0.0 - X --> fneg

lib/Target/X86/X86ISelLowering.cpp

@@ -2951,6 +2951,20 @@ static SDValue getMOVL(SelectionDAG &DAG, SDLoc dl, EVT VT, SDValue V1,
   return DAG.getVectorShuffle(VT, dl, V1, V2, &Mask[0]);
 }
 
+/// Check if the fall through instruction after a call site is unreachable.
+/// FIXME: This will fail if there are interesting non-code generating IR
+/// instructions between the call and the unreachable (lifetime.end). In
+/// practice, this should be rare because optimizations like to delete non-call
+/// code before unreachable.
+static bool isCallFollowedByUnreachable(ImmutableCallSite CS) {
+  const Instruction *NextInst;
+  if (auto *II = dyn_cast<InvokeInst>(CS.getInstruction()))
+    NextInst = II->getNormalDest()->getFirstNonPHIOrDbg();
+  else
+    NextInst = CS.getInstruction()->getNextNode();
+  return isa<UnreachableInst>(NextInst);
+}
+
 SDValue
 X86TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
                              SmallVectorImpl<SDValue> &InVals) const {
@@ -3456,6 +3470,15 @@ X86TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
     InFlag = Chain.getValue(1);
   }
 
+  if (Subtarget->isTargetWin64() && CLI.CS) {
+    // Look for a call followed by unreachable. On Win64, we need to ensure that
+    // the call does not accidentally fall through to something that looks like
+    // an epilogue. We do this by inserting a DEBUGTRAP, which lowers to int3,
+    // which is what MSVC emits after noreturn calls.
+    if (isCallFollowedByUnreachable(*CLI.CS))
+      Chain = DAG.getNode(ISD::DEBUGTRAP, dl, MVT::Other, Chain);
+  }
+
   // Handle result values, copying them out of physregs into vregs that we
   // return.
   return LowerCallResult(Chain, InFlag, CallConv, isVarArg,

lib/Target/X86/X86TargetMachine.cpp

@@ -110,13 +110,6 @@ X86TargetMachine::X86TargetMachine(const Target &T, const Triple &TT,
                         OL),
       TLOF(createTLOF(getTargetTriple())),
       Subtarget(TT, CPU, FS, *this, Options.StackAlignmentOverride) {
-  // Windows stack unwinder gets confused when execution flow "falls through"
-  // after a call to 'noreturn' function.
-  // To prevent that, we emit a trap for 'unreachable' IR instructions.
-  // (which on X86, happens to be the 'ud2' instruction)
-  if (Subtarget.isTargetWin64())
-    this->Options.TrapUnreachable = true;
-
   // By default (and when -ffast-math is on), enable estimate codegen for
   // everything except scalar division. By default, use 1 refinement step for
   // all operations. Defaults may be overridden by using command-line options.

test/CodeGen/X86/br-fold.ll

@@ -10,10 +10,10 @@
 ; X64_LINUX-NEXT: %bb8.i329
 
 ; X64_WINDOWS: orq %rax, %rcx
-; X64_WINDOWS-NEXT: ud2
+; X64_WINDOWS-NEXT: %bb8.i329
 
 ; X64_WINDOWS_GNU: orq %rax, %rcx
-; X64_WINDOWS_GNU-NEXT: ud2
+; X64_WINDOWS_GNU-NEXT: %bb8.i329
 
 @_ZN11xercesc_2_513SchemaSymbols21fgURI_SCHEMAFORSCHEMAE = external constant [33 x i16], align 32 ; <[33 x i16]*> [#uses=1]
 @_ZN11xercesc_2_56XMLUni16fgNotationStringE = external constant [9 x i16], align 16 ; <[9 x i16]*> [#uses=1]

test/CodeGen/X86/win-catchpad-rethrow.ll

@@ -0,0 +1,103 @@
+; RUN: llc -mtriple=x86_64-pc-windows-msvc < %s | FileCheck %s
+
+; C++ EH rethrows are interesting, because they are calls to noreturn
+; functions. There *must* be some code after the call instruction that doesn't
+; look like an epilogue. We use int3 to be consistent with MSVC.
+
+; Based on this C++ source:
+; int main() {
+;   try {
+;     throw 42;
+;   } catch (int) {
+;     try {
+;       throw;
+;     } catch (int) {
+;     }
+;   }
+;   return 0;
+; }
+
+; ModuleID = 't.cpp'
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+%rtti.TypeDescriptor2 = type { i8**, i8*, [3 x i8] }
+%eh.CatchableType = type { i32, i32, i32, i32, i32, i32, i32 }
+%eh.CatchableTypeArray.1 = type { i32, [1 x i32] }
+%eh.ThrowInfo = type { i32, i32, i32, i32 }
+
+$"\01??_R0H@8" = comdat any
+
+$"_CT??_R0H@84" = comdat any
+
+$_CTA1H = comdat any
+
+$_TI1H = comdat any
+
+@"\01??_7type_info@@6B@" = external constant i8*
+@"\01??_R0H@8" = linkonce_odr global %rtti.TypeDescriptor2 { i8** @"\01??_7type_info@@6B@", i8* null, [3 x i8] c".H\00" }, comdat
+@__ImageBase = external constant i8
+@"_CT??_R0H@84" = linkonce_odr unnamed_addr constant %eh.CatchableType { i32 1, i32 trunc (i64 sub nuw nsw (i64 ptrtoint (%rtti.TypeDescriptor2* @"\01??_R0H@8" to i64), i64 ptrtoint (i8* @__ImageBase to i64)) to i32), i32 0, i32 -1, i32 0, i32 4, i32 0 }, section ".xdata", comdat
+@_CTA1H = linkonce_odr unnamed_addr constant %eh.CatchableTypeArray.1 { i32 1, [1 x i32] [i32 trunc (i64 sub nuw nsw (i64 ptrtoint (%eh.CatchableType* @"_CT??_R0H@84" to i64), i64 ptrtoint (i8* @__ImageBase to i64)) to i32)] }, section ".xdata", comdat
+@_TI1H = linkonce_odr unnamed_addr constant %eh.ThrowInfo { i32 0, i32 0, i32 0, i32 trunc (i64 sub nuw nsw (i64 ptrtoint (%eh.CatchableTypeArray.1* @_CTA1H to i64), i64 ptrtoint (i8* @__ImageBase to i64)) to i32) }, section ".xdata", comdat
+
+define i32 @main() #0 personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+entry:
+  %tmp = alloca i32, align 4
+  store i32 42, i32* %tmp, align 4
+  %0 = bitcast i32* %tmp to i8*
+  invoke void @_CxxThrowException(i8* %0, %eh.ThrowInfo* nonnull @_TI1H) #1
+          to label %unreachable unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %entry
+  %1 = catchpad [%rtti.TypeDescriptor2* @"\01??_R0H@8", i32 0, i8* null]
+          to label %catch unwind label %catchendblock
+
+catch:                                            ; preds = %catch.dispatch
+  invoke void @_CxxThrowException(i8* null, %eh.ThrowInfo* null) #1
+          to label %unreachable unwind label %catch.dispatch.1
+
+catch.dispatch.1:                                 ; preds = %catch
+  %2 = catchpad [%rtti.TypeDescriptor2* @"\01??_R0H@8", i32 0, i8* null]
+          to label %catch.3 unwind label %catchendblock.2
+
+catch.3:                                          ; preds = %catch.dispatch.1
+  catchret %2 to label %try.cont
+
+try.cont:                                         ; preds = %catch.3
+  catchret %1 to label %try.cont.5
+
+try.cont.5:                                       ; preds = %try.cont
+  ret i32 0
+
+catchendblock.2:                                  ; preds = %catch.dispatch.1
+  catchendpad unwind label %catchendblock
+
+catchendblock:                                    ; preds = %catchendblock.2, %catch.dispatch
+  catchendpad unwind to caller
+
+unreachable:                                      ; preds = %catch, %entry
+  unreachable
+}
+
+declare void @_CxxThrowException(i8*, %eh.ThrowInfo*)
+
+declare i32 @__CxxFrameHandler3(...)
+
+attributes #0 = { "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-features"="+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { noreturn }
+
+; CHECK: main:
+; CHECK: .seh_proc main
+; CHECK: movl $42,
+; CHECK-DAG: leaq {{.*}}, %rcx
+; CHECK-DAG: leaq _TI1H(%rip), %rdx
+; CHECK: callq _CxxThrowException
+; CHECK-NEXT: int3
+
+; CHECK: "?catch$1@?0?main@4HA":
+; CHECK: .seh_proc "?catch$1@?0?main@4HA"
+; CHECK-DAG: xorl %ecx, %ecx
+; CHECK-DAG: xorl %edx, %edx
+; CHECK: callq _CxxThrowException
+; CHECK-NEXT: int3

test/CodeGen/X86/win64_call_epi.ll

@@ -24,9 +24,9 @@ catch:
 ; WIN64: nop
 ; WIN64: addq ${{[0-9]+}}, %rsp
 ; WIN64: retq
-; Check for 'ud2' after noreturn call
+; Check for 'int3' after noreturn call
 ; WIN64: callq _Unwind_Resume
-; WIN64-NEXT: ud2
+; WIN64-NEXT: int3
 ; WIN64: .seh_endproc