[CodeGen] Always use string computed in Sema for PredefinedExpr

We can't use any other string, anyway, because its type wouldn't
match the type of the PredefinedExpr.

With this change, we don't compute a "nice" name for the __func__ global
when it's used in the initializer for a constant. This doesn't seem like
a great loss, and I'm not sure how to fix it without either storing more
information in the AST, or somehow threading through the information
from ExprConstant.cpp.

This could break some situations involving BlockDecl; currently,
CodeGenFunction::EmitPredefinedLValue has some logic to intentionally
emit a string different from what Sema computed.  This code skips that
logic... but that logic can't work correctly in general anyway.  (For
example, sizeof(__func__) returns the wrong result.) Hopefully this
doesn't affect practical code.

Fixes https://bugs.llvm.org/show_bug.cgi?id=40313 .

Differential Revision: https://reviews.llvm.org/D56821

llvm-svn: 351766

clang/lib/CodeGen/CGExprConstant.cpp

@@ -1788,17 +1788,7 @@ ConstantLValueEmitter::VisitObjCStringLiteral(const ObjCStringLiteral *E) {
 
 ConstantLValue
 ConstantLValueEmitter::VisitPredefinedExpr(const PredefinedExpr *E) {
-  if (auto CGF = Emitter.CGF) {
-    LValue Res = CGF->EmitPredefinedLValue(E);
-    return cast<ConstantAddress>(Res.getAddress());
-  }
-
-  auto kind = E->getIdentKind();
-  if (kind == PredefinedExpr::PrettyFunction) {
-    return CGM.GetAddrOfConstantCString("top level", ".tmp");
-  }
-
-  return CGM.GetAddrOfConstantCString("", ".tmp");
+  return CGM.GetAddrOfConstantStringFromLiteral(E->getFunctionName());
 }
 
 ConstantLValue

clang/test/CodeGen/const-init.c

@@ -121,8 +121,8 @@ struct g22 {int x;} __attribute((packed));
 struct g23 {char a; short b; char c; struct g22 d;};
 struct g23 g24 = {1,2,3,4};
 
-// CHECK: @g25.g26 = internal global i8* getelementptr inbounds ([4 x i8], [4 x i8]* @__func__.g25, i32 0, i32 0)
-// CHECK: @__func__.g25 = private unnamed_addr constant [4 x i8] c"g25\00"
+// CHECK: @g25.g26 = internal global i8* getelementptr inbounds ([4 x i8], [4 x i8]* @[[FUNC:.*]], i32 0, i32 0)
+// CHECK: @[[FUNC]] = private unnamed_addr constant [4 x i8] c"g25\00"
 int g25() {
   static const char *g26 = __func__;
   return *g26;
@@ -153,7 +153,7 @@ void g29() {
       DCC_PASSWD passwd;
   } DCC_SRVR_NM;
   // CHECK: @g29.a = internal global %struct.DCC_SRVR_NM { [2 x i8] c"@\00" }, align 1
-  // CHECK: @g29.b = internal global [1 x i32] [i32 ptrtoint ([5 x i8]* @.str to i32)], align 4
+  // CHECK: @g29.b = internal global [1 x i32] [i32 ptrtoint ([5 x i8]* @.str.1 to i32)], align 4
   // CHECK: @g29.c = internal global [1 x i32] [i32 97], align 4
   static DCC_SRVR_NM a = { {"@"} };
   static int b[1] = { "asdf" }; // expected-warning {{incompatible pointer to integer conversion initializing 'int' with an expression of type 'char [5]'}}

clang/test/CodeGenCXX/predefined-expr-cxx14.cpp

@@ -20,6 +20,8 @@
 // CHECK-DAG: @__func__.___ZN16ClassBlockConstrD2Ev_block_invoke = private unnamed_addr constant [31 x i8] c"~ClassBlockConstr_block_invoke\00"
 // CHECK-DAG: @__func__.___ZN16ClassBlockConstrC2Ev_block_invoke = private unnamed_addr constant [30 x i8] c"ClassBlockConstr_block_invoke\00"
 
+// CHECK-DAG: private unnamed_addr constant [32 x i8] c"const char *ConstexprPrettyFn()\00"
+
 int printf(const char * _Format, ...);
 
 class ClassInTopLevelNamespace {
@@ -83,6 +85,11 @@ public:
   const char *getFunc() const { return Func; }
 };
 
+constexpr const char* ConstexprPrettyFn() {
+  return __PRETTY_FUNCTION__;
+}
+const char* ConstexprPrettyVar = ConstexprPrettyFn();
+
 int
 main() {
   int a;