[PATCH] D37425: LoopVectorize: MaxVF should not be larger than the loop trip count
Zvi Rackover via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Sep 4 01:36:41 PDT 2017
This revision was automatically updated to reflect the committed changes.
Closed by commit rL312472: LoopVectorize: MaxVF should not be larger than the loop trip count (authored by zvi).
Repository:
rL LLVM
https://reviews.llvm.org/D37425
Files:
llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
llvm/trunk/test/Transforms/LoopVectorize/X86/pr34438.ll
Index: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1960,7 +1960,7 @@
private:
/// \return An upper bound for the vectorization factor, larger than zero.
/// One is returned if vectorization should best be avoided due to cost.
- unsigned computeFeasibleMaxVF(bool OptForSize);
+ unsigned computeFeasibleMaxVF(bool OptForSize, unsigned ConstTripCount = 0);
/// The vectorization cost is a combination of the cost itself and a boolean
/// indicating whether any of the contributing operations will actually
@@ -6187,7 +6187,7 @@
return None;
}
- unsigned MaxVF = computeFeasibleMaxVF(OptForSize);
+ unsigned MaxVF = computeFeasibleMaxVF(OptForSize, TC);
if (TC % MaxVF != 0) {
// If the trip count that we found modulo the vectorization factor is not
@@ -6208,7 +6208,9 @@
return MaxVF;
}
-unsigned LoopVectorizationCostModel::computeFeasibleMaxVF(bool OptForSize) {
+unsigned
+LoopVectorizationCostModel::computeFeasibleMaxVF(bool OptForSize,
+ unsigned ConstTripCount) {
MinBWs = computeMinimumValueSizes(TheLoop->getBlocks(), *DB, &TTI);
unsigned SmallestType, WidestType;
std::tie(SmallestType, WidestType) = getSmallestAndWidestTypes();
@@ -6237,7 +6239,9 @@
if (MaxVectorSize == 0) {
DEBUG(dbgs() << "LV: The target has no vector registers.\n");
MaxVectorSize = 1;
- }
+ } else if (ConstTripCount && ConstTripCount < MaxVectorSize &&
+ isPowerOf2_32(ConstTripCount))
+ MaxVectorSize = ConstTripCount;
assert(MaxVectorSize <= 64 && "Did not expect to pack so many elements"
" into one vector!");
Index: llvm/trunk/test/Transforms/LoopVectorize/X86/pr34438.ll
===================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/X86/pr34438.ll
+++ llvm/trunk/test/Transforms/LoopVectorize/X86/pr34438.ll
@@ -0,0 +1,35 @@
+; PR34438
+; Loop has a short trip count of 8 iterations. It should be vectorized because no runtime checks or tail loop are necessary.
+; Two cases tested AVX (MaxVF=8 = TripCount) and AVX512 (MaxVF=16 > TripCount)
+
+; RUN: opt < %s -loop-vectorize -mtriple=x86_64-apple-macosx10.8.0 -mcpu=corei7-avx -S | FileCheck %s
+; RUN: opt < %s -loop-vectorize -mtriple=x86_64-apple-macosx10.8.0 -mcpu=skylake-avx512 -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"
+
+define void @small_tc(float* noalias nocapture %A, float* noalias nocapture readonly %B) {
+; CHECK-LABEL: @small_tc
+; CHECK: load <8 x float>, <8 x float>*
+; CHECK: fadd fast <8 x float>
+entry:
+ br label %for.body
+
+for.body:
+ %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+ %arrayidx = getelementptr inbounds float, float* %B, i64 %indvars.iv
+ %0 = load float, float* %arrayidx, align 4, !llvm.mem.parallel_loop_access !3
+ %arrayidx2 = getelementptr inbounds float, float* %A, i64 %indvars.iv
+ %1 = load float, float* %arrayidx2, align 4, !llvm.mem.parallel_loop_access !3
+ %add = fadd fast float %0, %1
+ store float %add, float* %arrayidx2, align 4, !llvm.mem.parallel_loop_access !3
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %exitcond = icmp eq i64 %indvars.iv.next, 8
+ br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !4
+
+for.end:
+ ret void
+}
+
+!3 = !{!3}
+!4 = !{!4}
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