[CodeGen] Fix some broken IR generated by -fsanitize=unsigned-integer-overflow

I think the author of the function assumed that `GetInsertBlock()`
wouldn't change from where `atomicPHI` was created, but this isn't
true when `-fsanitize=unsigned-integer-overflow` is enabled (we
generate an overflow/continuation label). Fix by keeping track of the
block we want to return to to complete the cmpxchg loop.

rdar://48406558

Differential revision: https://reviews.llvm.org/D58744

llvm-svn: 355054

1 files changed, 33 insertions, 0 deletions

diff --git a/clang/test/CodeGen/sanitize-atomic-int-overflow.c b/clang/test/CodeGen/sanitize-atomic-int-overflow.c
new file mode 100644
index 00000000000..a1064f47c34
--- /dev/null
+++ b/clang/test/CodeGen/sanitize-atomic-int-overflow.c
@@ -0,0 +1,33 @@
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.14.0 -fsanitize=unsigned-integer-overflow %s -emit-llvm -o - | FileCheck %s
+
+_Atomic(unsigned) atomic;
+
+// CHECK-LABEL: define void @cmpd_assign
+void cmpd_assign() {
+  // CHECK: br label %[[LOOP_START:.*]]
+
+  // CHECK: [[LOOP_START]]:
+  // CHECK-NEXT: phi i32 {{.*}}, [ {{.*}}, %[[INCOMING_BLOCK:.*]] ]
+
+  // CHECK: [[INCOMING_BLOCK]]:
+  // CHECK-NEXT: cmpxchg
+  // CHECK-NEXT: extractvalue
+  // CHECK-NEXT: extractvalue
+  // CHECK-NEXT: br i1 %8, label %{{.*}}, label %[[LOOP_START]]
+  atomic += 1;
+}
+
+// CHECK-LABEL: define void @inc
+void inc() {
+  // CHECK: br label %[[LOOP_START:.*]]
+
+  // CHECK: [[LOOP_START]]:
+  // CHECK-NEXT: phi i32 {{.*}}, [ {{.*}}, %[[INCOMING_BLOCK:.*]] ]
+
+  // CHECK: [[INCOMING_BLOCK]]:
+  // CHECK-NEXT: cmpxchg
+  // CHECK-NEXT: extractvalue
+  // CHECK-NEXT: extractvalue
+  // CHECK-NEXT: br i1 %8, label %{{.*}}, label %[[LOOP_START]]
+  atomic++;
+}