Patch by Vadim Chugunov
Win64 stack unwinder gets confused when execution flow "falls through" after
a call to 'noreturn' function. This fixes the "missing epilogue" problem by
emitting a trap instruction for IR 'unreachable' on x86_x64-pc-windows.
A secondary use for it would be for anyone wanting to make double-sure that
'noreturn' functions, indeed, do not return.
llvm-svn: 206684
diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index 09563fd..a5b7274 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -1041,8 +1041,10 @@
}
case Instruction::Unreachable:
- // Nothing to emit.
- return true;
+ if (TM.Options.TrapUnreachable)
+ return FastEmit_(MVT::Other, MVT::Other, ISD::TRAP) != 0;
+ else
+ return true;
case Instruction::Alloca:
// FunctionLowering has the static-sized case covered.
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 06cd8b3..1aaac5f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2765,6 +2765,11 @@
getValue(I.getAddress())));
}
+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
Type *Ty = I.getType();
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 290d83a..a04108d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -642,7 +642,7 @@
void visitBr(const BranchInst &I);
void visitSwitch(const SwitchInst &I);
void visitIndirectBr(const IndirectBrInst &I);
- void visitUnreachable(const UnreachableInst &I) { /* noop */ }
+ void visitUnreachable(const UnreachableInst &I);
// Helpers for visitSwitch
bool handleSmallSwitchRange(CaseRec& CR,