[CodeGen] Tweak isTriviallyRecursive further

isTriviallyRecursive is a hack used to bridge a gap between the
expectations that source code assumes and the semantics that LLVM IR can
provide.  Specifically, asm labels on functions are treated as an
explicit name for a GlobalObject in Clang but treated like an
output-processing step in GCC.  Tweak this hack a little further to emit
calls to library functions instead of emitting an incorrect definition.
The definition in question would have available_externally linkage (this
is OK) but result in a call to itself which will either result in an
infinite loop or stack overflow.

This fixes PR23964.

llvm-svn: 241043

2 files changed, 8 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 461f694acb0..ea09ba8d4fb 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1457,12 +1457,7 @@ CodeGenModule::isTriviallyRecursive(const FunctionDecl *FD) {
     Name = FD->getName();
   }
 
-  auto &BI = Context.BuiltinInfo;
-  unsigned BuiltinID = Context.Idents.get(Name).getBuiltinID();
-  if (!BuiltinID || !BI.isPredefinedLibFunction(BuiltinID))
-    return false;
-
-  FunctionIsDirectlyRecursive Walker(Name, BI);
+  FunctionIsDirectlyRecursive Walker(Name, Context.BuiltinInfo);
   Walker.TraverseFunctionDecl(const_cast<FunctionDecl*>(FD));
   return Walker.Result;
 }
diff --git a/clang/test/CodeGen/pr9614.c b/clang/test/CodeGen/pr9614.c
index de21dbbb23f..63cb5af1868 100644
--- a/clang/test/CodeGen/pr9614.c
+++ b/clang/test/CodeGen/pr9614.c
@@ -18,11 +18,16 @@ prefetch(void) {
   __builtin_prefetch(0, 0, 1);
 }
 
+extern inline __attribute__((__always_inline__, __gnu_inline__)) void *memchr(void *__s, int __c, __SIZE_TYPE__ __n) {
+  return __builtin_memchr(__s, __c, __n);
+}
+
 void f(void) {
   foo();
   abs(0);
   strrchr_foo("", '.');
   prefetch();
+  memchr("", '.', 0);
 }
 
 // CHECK-LABEL: define void @f()
@@ -30,9 +35,11 @@ void f(void) {
 // CHECK: call i32 @abs(i32 0)
 // CHECK: call i8* @strrchr(
 // CHECK: call void @llvm.prefetch(
+// CHECK: call i8* @memchr(
 // CHECK: ret void
 
 // CHECK: declare void @foo()
 // CHECK: declare i32 @abs(i32
 // CHECK: declare i8* @strrchr(i8*, i32)
+// CHECK: declare i8* @memchr(
 // CHECK: declare void @llvm.prefetch(