DataFlowSanitizer: correctly combine labels in the case where they are equal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189133 91177308-0d34-0410-b5e6-96231b3b80d8

Author: pcc

lib/Transforms/Instrumentation/DataFlowSanitizer.cpp

@@ -775,7 +775,7 @@ Value *DataFlowSanitizer::combineShadows(Value *V1, Value *V2,
     BasicBlock *Tail = BI->getSuccessor(0);
     PHINode *Phi = PHINode::Create(ShadowTy, 2, "", Tail->begin());
     Phi->addIncoming(Call, Call->getParent());
-    Phi->addIncoming(ZeroShadow, Head);
+    Phi->addIncoming(V1, Head);
     Pos = Phi;
     return Phi;
   } else {

test/Instrumentation/DataFlowSanitizer/arith.ll

@@ -3,11 +3,12 @@ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f3
 
 define i8 @add(i8 %a, i8 %b) {
   ; CHECK: @"dfs$add"
-  ; CHECK: load{{.*}}__dfsan_arg_tls
-  ; CHECK: load{{.*}}__dfsan_arg_tls
-  ; CHECK: call{{.*}}__dfsan_union
+  ; CHECK-DAG: %[[ALABEL:.*]] = load{{.*}}__dfsan_arg_tls, i64 0, i64 0
+  ; CHECK-DAG: %[[BLABEL:.*]] = load{{.*}}__dfsan_arg_tls, i64 0, i64 1
+  ; CHECK: %[[UNION:.*]] = call{{.*}}__dfsan_union(i16 zeroext %[[ALABEL]], i16 zeroext %[[BLABEL]])
+  ; CHECK: %[[ADDLABEL:.*]] = phi i16 [ %[[UNION]], {{.*}} ], [ %[[ALABEL]], {{.*}} ]
   ; CHECK: add i8
-  ; CHECK: store{{.*}}__dfsan_retval_tls
+  ; CHECK: store i16 %[[ADDLABEL]], i16* @__dfsan_retval_tls
   ; CHECK: ret i8
   %c = add i8 %a, %b
   ret i8 %c