[codegen]Ensure __builtin_trap() has an unreachable

clang/lib/CodeGen/CGBuiltin.cpp

@@ -4020,9 +4020,18 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     Function *F = CGM.getIntrinsic(Intrinsic::clear_cache, {CGM.DefaultPtrTy});
     return RValue::get(Builder.CreateCall(F, {Begin, End}));
   }
-  case Builtin::BI__builtin_trap:
-    EmitTrapCall(Intrinsic::trap);
+  case Builtin::BI__builtin_trap: {
+    llvm::CallInst *Trap = EmitTrapCall(Intrinsic::trap);
+    Trap->setDoesNotReturn();
+    Trap->setDoesNotThrow();
+    Builder.CreateUnreachable();
+    if (Builder.GetInsertBlock()) {
+      // Dummy block for the ret void - it'll be cleaned up.
+      llvm::BasicBlock *DeadBB = createBasicBlock("dead.trap");
+      EmitBlock(DeadBB);
+    }
     return RValue::get(nullptr);
+  }
   case Builtin::BI__builtin_verbose_trap: {
     llvm::DILocation *TrapLocation = Builder.getCurrentDebugLocation();
     if (getDebugInfo()) {

clang/test/CodeGen/amdgpu-builtin-is-invocable.c

@@ -20,7 +20,7 @@
 // AMDGCN-GFX1010-SAME: ) #[[ATTR0:[0-9]+]] {
 // AMDGCN-GFX1010-NEXT:  [[ENTRY:.*:]]
 // AMDGCN-GFX1010-NEXT:    call void @llvm.trap()
-// AMDGCN-GFX1010-NEXT:    ret void
+// AMDGCN-GFX1010-NEXT:    unreachable
 //
 // AMDGCNSPIRV-LABEL: define spir_func void @foo(
 // AMDGCNSPIRV-SAME: ) addrspace(4) #[[ATTR0:[0-9]+]] {
@@ -38,6 +38,8 @@
 // AMDGCNSPIRV-NEXT:    br i1 [[TOBOOL3]], label %[[IF_THEN]], label %[[IF_END:.*]]
 // AMDGCNSPIRV:       [[IF_THEN]]:
 // AMDGCNSPIRV-NEXT:    call addrspace(4) void @llvm.trap()
+// AMDGCNSPIRV-NEXT:    unreachable
+// AMDGCNSPIRV:        dead.trap:
 // AMDGCNSPIRV-NEXT:    br label %[[IF_END]]
 // AMDGCNSPIRV:       [[IF_END]]:
 // AMDGCNSPIRV-NEXT:    ret void

clang/test/CodeGen/amdgpu-builtin-processor-is.c

@@ -14,6 +14,8 @@
 // AMDGCN-GFX900-SAME: ) #[[ATTR0:[0-9]+]] {
 // AMDGCN-GFX900-NEXT:  [[ENTRY:.*:]]
 // AMDGCN-GFX900-NEXT:    call void @llvm.trap()
+// AMDGCN-GFX900-NEXT:    unreachable
+// AMDGCN-GFX900:       dead.trap:
 // AMDGCN-GFX900-NEXT:    ret void
 //
 // AMDGCN-GFX1010-LABEL: define dso_local void @foo(
@@ -45,6 +47,8 @@
 // AMDGCNSPIRV-NEXT:    br i1 [[TOBOOL7]], label %[[IF_THEN]], label %[[IF_END:.*]]
 // AMDGCNSPIRV:       [[IF_THEN]]:
 // AMDGCNSPIRV-NEXT:    call addrspace(4) void @llvm.trap()
+// AMDGCNSPIRV-NEXT:    unreachable
+// AMDGCNSPIRV:       dead.trap:    
 // AMDGCNSPIRV-NEXT:    br label %[[IF_END]]
 // AMDGCNSPIRV:       [[IF_END]]:
 // AMDGCNSPIRV-NEXT:    ret void

clang/test/CodeGen/attr-nomerge.cpp

@@ -100,10 +100,9 @@ void something_else_again() {
 // CHECK: load ptr, ptr
 // CHECK: %[[AG:.*]] = load ptr, ptr
 // CHECK-NEXT: call void %[[AG]](ptr {{.*}}) #[[ATTR1]]
-// CHECK: call void @llvm.trap() #[[ATTR0]]
-// CHECK: call void @llvm.debugtrap() #[[ATTR0]]
-// CHECK: call void @llvm.trap() #[[ATTR0]]
-// CHECK: call void  @_ZN1AD1Ev(ptr {{.*}}) #[[ATTR1]]
+// CHECK: call void @llvm.trap() #[[ATTR8:[0-9]+]]
+// CHECK: unreachable
 
 // CHECK-DAG: attributes #[[ATTR0]] = {{{.*}}nomerge{{.*}}}
 // CHECK-DAG: attributes #[[ATTR1]] = {{{.*}}nomerge{{.*}}}
+// CHECK-DAG  attributes #[[ATTR8]] = { nomerge noreturn nounwind }

clang/test/CodeGen/pr53127.cpp

@@ -15,6 +15,8 @@ void operator delete(void*);
 // CHECK-NEXT:    br i1 [[CALL]], label [[COND_TRUE:%.*]], label [[COND_FALSE:%.*]]
 // CHECK:       cond.true:
 // CHECK-NEXT:    call void @llvm.trap()
+// CHECK-NEXT:    unreachable
+// CHECK:       dead.trap:
 // CHECK-NEXT:    br label [[COND_END:%.*]]
 // CHECK:       cond.false:
 // CHECK-NEXT:    br label [[COND_END]]

clang/test/CodeGenCXX/microsoft-abi-byval-vararg.cpp

@@ -41,6 +41,7 @@ void call_var_args() {
 }
 
 // CHECK-LABEL: define dso_local void @"?call_var_args@@YAXXZ"()
+// FIXME all of these are after the trap so they should be gone.
 // CHECK: call void {{.*varargs_zero.*}}(ptr inalloca(<{ %struct.A }>) %{{.*}})
 // CHECK: call void {{.*varargs_one.*}}(ptr inalloca(<{ i32, %struct.A }>) %{{.*}})
 // CHECK: call void {{.*varargs_two.*}}(ptr inalloca(<{ i32, i32, %struct.A }>) %{{.*}})

clang/test/CodeGenCXX/trap-fnattr.cpp

@@ -30,7 +30,7 @@ int test_add_overflow(int a, int b) {
   return a + b;
 }
 
-// TRAPFUNC: attributes [[ATTR0]] = { {{.*}}"trap-func-name"="mytrap" }
+// TRAPFUNC: attributes [[ATTR0]] = { noreturn no unwind "trap-func-name"="mytrap" }
 // TRAPFUNC: attributes [[ATTR1]] = { {{.*}}"trap-func-name"="mytrap" }
 
 // NOOPTION-NOT: attributes [[ATTR2]] = { {{.*}}"trap-func-name"="mytrap" }