[LoopUnrollRuntime] Remove strict assert about VMap requirement

When unrolling under multiple exits which is under off-by-default option,
the assert that checks for VMap entry in loop exit values is too strong.
(assert if VMap entry did not exist, the value should be a
constant). However, values derived from
constants or from values outside loop, does not have a VMap entry too.

Removed the assert and added a testcase showcasing the property for
non-constant values.

llvm-svn: 307542

1 files changed, 3 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 8733a1388df..59408ffe7a7 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -710,11 +710,10 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
      // node.
      for (unsigned i =0; i < oldNumOperands; i++){
        Value *newVal = VMap[Phi->getIncomingValue(i)];
-       if (!newVal) {
-         assert(isa<Constant>(Phi->getIncomingValue(i)) &&
-                "VMap should exist for all values except constants!");
+       // newVal can be a constant or derived from values outside the loop, and
+       // hence need not have a VMap value.
+       if (!newVal)
          newVal = Phi->getIncomingValue(i);
-       }
        Phi->addIncoming(newVal,
                            cast<BasicBlock>(VMap[Phi->getIncomingBlock(i)]));
      }