4 files changed, 26 insertions, 6 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 4225bd54c89..74c50d2a246 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2625,9 +2625,23 @@ void SelectionDAGBuilder::visitIndirectBr(const IndirectBrInst &I) {
 }
 
 void SelectionDAGBuilder::visitUnreachable(const UnreachableInst &I) {
-  if (DAG.getTarget().Options.TrapUnreachable)
-    DAG.setRoot(
-        DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, DAG.getRoot()));
+  if (!DAG.getTarget().Options.TrapUnreachable)
+    return;
+
+  // We may be able to ignore unreachable behind a noreturn call.
+  if (DAG.getTarget().Options.NoTrapAfterNoreturn) {
+    const BasicBlock &BB = *I.getParent();
+    if (&I != &BB.front()) {
+      BasicBlock::const_iterator PredI =
+        std::prev(BasicBlock::const_iterator(&I));
+      if (const CallInst *Call = dyn_cast<CallInst>(&*PredI)) {
+        if (Call->doesNotReturn())
+          return;
+      }
+    }
+  }
+
+  DAG.setRoot(DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, DAG.getRoot()));
 }
 
 void SelectionDAGBuilder::visitFSub(const User &I) {
diff --git a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
index d7dea46a351..b25bcdb7edc 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
@@ -244,8 +244,10 @@ AArch64TargetMachine::AArch64TargetMachine(const Target &T, const Triple &TT,
       TLOF(createTLOF(getTargetTriple())), isLittle(LittleEndian) {
   initAsmInfo();
 
-  if (TT.isOSBinFormatMachO())
+  if (TT.isOSBinFormatMachO()) {
     this->Options.TrapUnreachable = true;
+    this->Options.NoTrapAfterNoreturn = true;
+  }
 
   // Enable GlobalISel at or below EnableGlobalISelAt0.
   if (getOptLevel() <= EnableGlobalISelAtO)
diff --git a/llvm/lib/Target/ARM/ARMTargetMachine.cpp b/llvm/lib/Target/ARM/ARMTargetMachine.cpp
index 6a7f4814d1c..bc2525b6b42 100644
--- a/llvm/lib/Target/ARM/ARMTargetMachine.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetMachine.cpp
@@ -239,8 +239,10 @@ ARMBaseTargetMachine::ARMBaseTargetMachine(const Target &T, const Triple &TT,
       this->Options.EABIVersion = EABI::EABI5;
   }
 
-  if (TT.isOSBinFormatMachO())
+  if (TT.isOSBinFormatMachO()) {
     this->Options.TrapUnreachable = true;
+    this->Options.NoTrapAfterNoreturn = true;
+  }
 
   initAsmInfo();
 }
diff --git a/llvm/lib/Target/X86/X86TargetMachine.cpp b/llvm/lib/Target/X86/X86TargetMachine.cpp
index 8402434cd47..9b45e3bddc8 100644
--- a/llvm/lib/Target/X86/X86TargetMachine.cpp
+++ b/llvm/lib/Target/X86/X86TargetMachine.cpp
@@ -229,8 +229,10 @@ X86TargetMachine::X86TargetMachine(const Target &T, const Triple &TT,
   // to ever want to mix 32 and 64-bit windows code in a single module
   // this should be fine.
   if ((TT.isOSWindows() && TT.getArch() == Triple::x86_64) || TT.isPS4() ||
-      TT.isOSBinFormatMachO())
+      TT.isOSBinFormatMachO()) {
     this->Options.TrapUnreachable = true;
+    this->Options.NoTrapAfterNoreturn = TT.isOSBinFormatMachO();
+  }
 
   initAsmInfo();
 }