diff options
Diffstat (limited to 'llvm')
| -rw-r--r-- | llvm/lib/Transforms/Scalar/GVN.cpp | 4 | ||||
| -rw-r--r-- | llvm/test/Transforms/GVN/br-identical.ll | 38 |
2 files changed, 42 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp index e93833c32f4..60903c8b4aa 100644 --- a/llvm/lib/Transforms/Scalar/GVN.cpp +++ b/llvm/lib/Transforms/Scalar/GVN.cpp @@ -2804,6 +2804,10 @@ bool GVN::processFoldableCondBr(BranchInst *BI) { if (!BI || BI->isUnconditional()) return false; + // If a branch has two identical successors, we cannot declare either dead. + if (BI->getSuccessor(0) == BI->getSuccessor(1)) + return false; + ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition()); if (!Cond) return false; diff --git a/llvm/test/Transforms/GVN/br-identical.ll b/llvm/test/Transforms/GVN/br-identical.ll new file mode 100644 index 00000000000..dfb7abe9a5d --- /dev/null +++ b/llvm/test/Transforms/GVN/br-identical.ll @@ -0,0 +1,38 @@ +; RUN: opt -gvn -S -o - %s | FileCheck %s + +; If a branch has two identical successors, we cannot declare either dead. + +define void @widget(i1 %p) { +entry: + br label %bb2 + +bb2: + %t1 = phi i64 [ 0, %entry ], [ %t5, %bb7 ] + %t2 = add i64 %t1, 1 + %t3 = icmp ult i64 0, %t2 + br i1 %t3, label %bb3, label %bb4 + +bb3: + %t4 = call i64 @f() + br label %bb4 + +bb4: + ; CHECK-NOT: phi {{.*}} undef + %foo = phi i64 [ %t4, %bb3 ], [ 0, %bb2 ] + br i1 %p, label %bb5, label %bb6 + +bb5: + br i1 true, label %bb7, label %bb7 + +bb6: + br i1 true, label %bb7, label %bb7 + +bb7: + %t5 = add i64 %t1, 1 + br i1 %p, label %bb2, label %bb8 + +bb8: + ret void +} + +declare i64 @f() |
