Relax the "don't unroll loops containing calls" rule. Instead, when a loop contains a call, lower the

unrolling threshold to the optimize-for-size threshold.  Basically, for loops containing calls, unrolling
can still be profitable as long as the loop is REALLY small.

llvm-svn: 113439

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index f20f7dc5d6d..f0a661cb699 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -132,8 +132,10 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
     unsigned LoopSize = ApproximateLoopSize(L, NumCalls);
     DEBUG(dbgs() << "  Loop Size = " << LoopSize << "\n");
     if (NumCalls != 0) {
-      DEBUG(dbgs() << "  Not unrolling loop with function calls.\n");
-      return false;
+      // Even for a loop that contains calls, it can still be profitable to
+      // unroll if the loop is really, REALLY small.
+      DEBUG(dbgs() <<"  Using lower threshold for loop with function calls.\n");
+      CurrentThreshold = OptSizeUnrollThreshold;
     }
     uint64_t Size = (uint64_t)LoopSize*Count;
     if (TripCount != 1 && Size > CurrentThreshold) {