LoopUnroll: If we're doing partial unrolling, use the PartialThreshold to limit unrolling.

Otherwise we use the same threshold as for complete unrolling, which is
way too high. This made us unroll any loop smaller than 150 instructions
by 8 times, but only if someone specified -march=core2 or better,
which happens to be the default on darwin.

llvm-svn: 207940

1 files changed, 6 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index 3290c6ff45b..fc28fd2bdce 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -238,9 +238,12 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
       return false;
     }
     uint64_t Size = (uint64_t)LoopSize*Count;
-    if (TripCount != 1 && Size > Threshold) {
-      DEBUG(dbgs() << "  Too large to fully unroll with count: " << Count
-            << " because size: " << Size << ">" << Threshold << "\n");
+    if (TripCount != 1 &&
+        (Size > Threshold || (Count != TripCount && Size > PartialThreshold))) {
+      if (Size > Threshold)
+        DEBUG(dbgs() << "  Too large to fully unroll with count: " << Count
+                     << " because size: " << Size << ">" << Threshold << "\n");
+
       bool AllowPartial = UserAllowPartial ? CurrentAllowPartial : UP.Partial;
       if (!AllowPartial && !(Runtime && TripCount == 0)) {
         DEBUG(dbgs() << "  will not try to unroll partially because "