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| author | Nadav Rotem <nrotem@apple.com> | 2012-10-31 03:31:07 +0000 |
|---|---|---|
| committer | Nadav Rotem <nrotem@apple.com> | 2012-10-31 03:31:07 +0000 |
| commit | 5b2c4dc5f8f70352f029d595797089821eb39b3c (patch) | |
| tree | 5ffb655cdd74ec272750c49407181271f76c5f98 | |
| parent | 42d43351b274603ed0ac28128498a35b8987ce15 (diff) | |
| download | external_llvm-5b2c4dc5f8f70352f029d595797089821eb39b3c.zip external_llvm-5b2c4dc5f8f70352f029d595797089821eb39b3c.tar.gz external_llvm-5b2c4dc5f8f70352f029d595797089821eb39b3c.tar.bz2 | |
LoopVectorize: Do not vectorize loops with tiny constant trip counts.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167101 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | lib/Transforms/Vectorize/LoopVectorize.cpp | 8 | ||||
| -rw-r--r-- | test/Transforms/LoopVectorize/small-loop.ll | 33 |
2 files changed, 41 insertions, 0 deletions
diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp index e82dfa2..fd728bd 100644 --- a/lib/Transforms/Vectorize/LoopVectorize.cpp +++ b/lib/Transforms/Vectorize/LoopVectorize.cpp @@ -1145,6 +1145,14 @@ bool LoopVectorizationLegality::canVectorize() { return false; } + // Do not loop-vectorize loops with a tiny trip count. + unsigned TC = SE->getSmallConstantTripCount(TheLoop, BB); + if (TC > 0 && TC < 16) { + DEBUG(dbgs() << "LV: Found a loop with a very small trip count. " << + "This loop is not worth vectorizing.\n"); + return false; + } + DEBUG(dbgs() << "LV: We can vectorize this loop!\n"); // Okay! We can vectorize. At this point we don't have any other mem analysis diff --git a/test/Transforms/LoopVectorize/small-loop.ll b/test/Transforms/LoopVectorize/small-loop.ll new file mode 100644 index 0000000..4a6e4b2 --- /dev/null +++ b/test/Transforms/LoopVectorize/small-loop.ll @@ -0,0 +1,33 @@ +; RUN: opt < %s -loop-vectorize -force-vector-width=4 -dce -instcombine -licm -S | FileCheck %s + +target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128" +target triple = "x86_64-apple-macosx10.8.0" + +@a = common global [2048 x i32] zeroinitializer, align 16 +@b = common global [2048 x i32] zeroinitializer, align 16 +@c = common global [2048 x i32] zeroinitializer, align 16 + +;CHECK: @example1 +;CHECK-NOT: load <4 x i32> +;CHECK: ret void +define void @example1() nounwind uwtable ssp { + br label %1 + +; <label>:1 ; preds = %1, %0 + %indvars.iv = phi i64 [ 0, %0 ], [ %indvars.iv.next, %1 ] + %2 = getelementptr inbounds [2048 x i32]* @b, i64 0, i64 %indvars.iv + %3 = load i32* %2, align 4 + %4 = getelementptr inbounds [2048 x i32]* @c, i64 0, i64 %indvars.iv + %5 = load i32* %4, align 4 + %6 = add nsw i32 %5, %3 + %7 = getelementptr inbounds [2048 x i32]* @a, i64 0, i64 %indvars.iv + store i32 %6, i32* %7, align 4 + %indvars.iv.next = add i64 %indvars.iv, 1 + %lftr.wideiv = trunc i64 %indvars.iv.next to i32 + %exitcond = icmp eq i32 %lftr.wideiv, 8 ; <----- A really small trip count. + br i1 %exitcond, label %8, label %1 + +; <label>:8 ; preds = %1 + ret void +} + |