[llvm] r329042 - peel loops with runtime small trip counts
Ikhlas Ajbar via llvm-commits
llvm-commits at lists.llvm.org
Mon Apr 2 20:39:43 PDT 2018
Author: iajbar
Date: Mon Apr 2 20:39:43 2018
New Revision: 329042
URL: http://llvm.org/viewvc/llvm-project?rev=329042&view=rev
Log:
peel loops with runtime small trip counts
For Hexagon, peeling loops with small runtime trip count is beneficial for our
benchmarks. We set PeelCount in HexagonTargetInfo.cpp and we use PeelCount set
by the target for computing the desired peel count.
Differential Revision: https://reviews.llvm.org/D44880
Added:
llvm/trunk/test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll
Modified:
llvm/trunk/include/llvm/Transforms/Utils/UnrollLoop.h
llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp
llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
Modified: llvm/trunk/include/llvm/Transforms/Utils/UnrollLoop.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/UnrollLoop.h?rev=329042&r1=329041&r2=329042&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/UnrollLoop.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/UnrollLoop.h Mon Apr 2 20:39:43 2018
@@ -73,6 +73,8 @@ void computePeelCount(Loop *L, unsigned
TargetTransformInfo::UnrollingPreferences &UP,
unsigned &TripCount, ScalarEvolution &SE);
+bool canPeel(Loop *L);
+
bool peelLoop(Loop *L, unsigned PeelCount, LoopInfo *LI, ScalarEvolution *SE,
DominatorTree *DT, AssumptionCache *AC, bool PreserveLCSSA);
Modified: llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp?rev=329042&r1=329041&r2=329042&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp (original)
+++ llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp Mon Apr 2 20:39:43 2018
@@ -44,6 +44,13 @@ HexagonTTIImpl::getPopcntSupport(unsigne
void HexagonTTIImpl::getUnrollingPreferences(Loop *L, ScalarEvolution &SE,
TTI::UnrollingPreferences &UP) {
UP.Runtime = UP.Partial = true;
+ // Only try to peel innermost loops with small runtime trip counts.
+ if (L && L->empty() &&
+ SE.getSmallConstantTripCount(L) == 0 &&
+ SE.getSmallConstantMaxTripCount(L) > 0 &&
+ SE.getSmallConstantMaxTripCount(L) <= 5) {
+ UP.PeelCount = 2;
+ }
}
bool HexagonTTIImpl::shouldFavorPostInc() const {
Modified: llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp?rev=329042&r1=329041&r2=329042&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp Mon Apr 2 20:39:43 2018
@@ -978,6 +978,9 @@ static LoopUnrollResult tryToUnrollLoop(
if (UP.Threshold == 0 && (!UP.Partial || UP.PartialThreshold == 0))
return LoopUnrollResult::Unmodified;
+ if (UP.PeelCount && !canPeel(L))
+ UP.PeelCount = 0;
+
SmallPtrSet<const Value *, 32> EphValues;
CodeMetrics::collectEphemeralValues(L, &AC, EphValues);
Modified: llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp?rev=329042&r1=329041&r2=329042&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp Mon Apr 2 20:39:43 2018
@@ -69,7 +69,7 @@ static const unsigned InfiniteIterations
std::numeric_limits<unsigned>::max();
// Check whether we are capable of peeling this loop.
-static bool canPeel(Loop *L) {
+bool llvm::canPeel(Loop *L) {
// Make sure the loop is in simplified form
if (!L->isLoopSimplifyForm())
return false;
@@ -221,6 +221,9 @@ void llvm::computePeelCount(Loop *L, uns
TargetTransformInfo::UnrollingPreferences &UP,
unsigned &TripCount, ScalarEvolution &SE) {
assert(LoopSize > 0 && "Zero loop size is not allowed!");
+ // Save the UP.PeelCount value set by the target in
+ // TTI.getUnrollingPreferences or by the flag -unroll-peel-count.
+ unsigned TargetPeelCount = UP.PeelCount;
UP.PeelCount = 0;
if (!canPeel(L))
return;
@@ -240,7 +243,9 @@ void llvm::computePeelCount(Loop *L, uns
SmallDenseMap<PHINode *, unsigned> IterationsToInvariance;
// Now go through all Phis to calculate their the number of iterations they
// need to become invariants.
- unsigned DesiredPeelCount = 0;
+ // Start the max computation with the UP.PeelCount value set by the target
+ // in TTI.getUnrollingPreferences or by the flag -unroll-peel-count.
+ unsigned DesiredPeelCount = TargetPeelCount;
BasicBlock *BackEdge = L->getLoopLatch();
assert(BackEdge && "Loop is not in simplified form?");
for (auto BI = L->getHeader()->begin(); isa<PHINode>(&*BI); ++BI) {
Added: llvm/trunk/test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll?rev=329042&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll (added)
+++ llvm/trunk/test/Transforms/LoopUnroll/Hexagon/peel-small-loop.ll Mon Apr 2 20:39:43 2018
@@ -0,0 +1,37 @@
+; RUN: opt -loop-unroll -mtriple=hexagon -S < %s | FileCheck %s
+; Check that the loop is peeled twice for Hexagon.
+; CHECK: while.body.peel
+; CHECK: while.body.peel2
+
+%struct.STREAM = type { %union.anon, i32, i32 }
+%union.anon = type { i32* }
+
+define void @function(%struct.STREAM* nocapture readonly %b) local_unnamed_addr {
+entry:
+ %bitPtr3 = getelementptr inbounds %struct.STREAM, %struct.STREAM* %b, i32 0, i32 2
+ %0 = load i32, i32* %bitPtr3, align 4
+ %cmp11 = icmp ult i32 %0, 32
+ br i1 %cmp11, label %while.body.preheader, label %do.end
+
+while.body.preheader:
+ %value2 = getelementptr inbounds %struct.STREAM, %struct.STREAM* %b, i32 0, i32 1
+ %1 = load i32, i32* %value2, align 4
+ %w = getelementptr inbounds %struct.STREAM, %struct.STREAM* %b, i32 0, i32 0, i32 0
+ %2 = load i32*, i32** %w, align 4
+ br label %while.body
+
+while.body:
+ %bitPtr.014 = phi i32 [ %add, %while.body ], [ %0, %while.body.preheader ]
+ %value.013 = phi i32 [ %shl, %while.body ], [ %1, %while.body.preheader ]
+ %ptr.012 = phi i32* [ %incdec.ptr, %while.body ], [ %2, %while.body.preheader ]
+ %add = add nuw i32 %bitPtr.014, 8
+ %shr = lshr i32 %value.013, 24
+ %incdec.ptr = getelementptr inbounds i32, i32* %ptr.012, i32 1
+ store i32 %shr, i32* %ptr.012, align 4
+ %shl = shl i32 %value.013, 8
+ %cmp = icmp ult i32 %add, 17
+ br i1 %cmp, label %while.body, label %do.end
+
+do.end:
+ ret void
+}
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