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

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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207940 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LoopUnrollPass.cpp b/lib/Transforms/Scalar/LoopUnrollPass.cpp
index 3290c6ff45bb7faf31cbc283f9424b13633ba39f..fc28fd2bdce263aa15d289fe2bad4933074e3410 100644 (file)
--- a/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/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 "

diff --git a/test/Transforms/LoopUnroll/X86/partial.ll b/test/Transforms/LoopUnroll/X86/partial.ll
index 15867cbea0acf13fd8e52c72b5ec7dc81999c58b..75b9c3fb89a69a1b7c3c4441765c8e43891d9485 100644 (file)
--- a/test/Transforms/LoopUnroll/X86/partial.ll
+++ b/test/Transforms/LoopUnroll/X86/partial.ll
@@ -76,5 +76,52 @@ for.end:                                          ; preds = %vector.body
   ret void
 }
 
+define zeroext i16 @test1(i16* nocapture readonly %arr, i32 %n) #0 {
+entry:
+  %cmp25 = icmp eq i32 %n, 0
+  br i1 %cmp25, label %for.end, label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
+  %reduction.026 = phi i16 [ %add14, %for.body ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i16* %arr, i64 %indvars.iv
+  %0 = load i16* %arrayidx, align 2
+  %add = add i16 %0, %reduction.026
+  %sext = mul i64 %indvars.iv, 12884901888
+  %idxprom3 = ashr exact i64 %sext, 32
+  %arrayidx4 = getelementptr inbounds i16* %arr, i64 %idxprom3
+  %1 = load i16* %arrayidx4, align 2
+  %add7 = add i16 %add, %1
+  %sext28 = mul i64 %indvars.iv, 21474836480
+  %idxprom10 = ashr exact i64 %sext28, 32
+  %arrayidx11 = getelementptr inbounds i16* %arr, i64 %idxprom10
+  %2 = load i16* %arrayidx11, align 2
+  %add14 = add i16 %add7, %2
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, %n
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body, %entry
+  %reduction.0.lcssa = phi i16 [ 0, %entry ], [ %add14, %for.body ]
+  ret i16 %reduction.0.lcssa
+
+; This loop is too large to be partially unrolled (size=16)
+
+; CHECK-LABEL: @test1
+; CHECK: br
+; CHECK: br
+; CHECK: br
+; CHECK: br
+; CHECK-NOT: br
+
+; CHECK-NOUNRL-LABEL: @test1
+; CHECK-NOUNRL: br
+; CHECK-NOUNRL: br
+; CHECK-NOUNRL: br
+; CHECK-NOUNRL: br
+; CHECK-NOUNRL-NOT: br
+}
+
 attributes #0 = { nounwind uwtable }