[llvm] r331037 - [LoopInterchange] Allow some loops with PHI nodes in the exit block.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Fri Apr 27 06:52:51 PDT 2018
Author: fhahn
Date: Fri Apr 27 06:52:51 2018
New Revision: 331037
URL: http://llvm.org/viewvc/llvm-project?rev=331037&view=rev
Log:
[LoopInterchange] Allow some loops with PHI nodes in the exit block.
We currently support LCSSA PHI nodes in the outer loop exit, if their
incoming values do not come from the outer loop latch or if the
outer loop latch has a single predecessor. In that case, the outer loop latch
will be executed only if the inner loop gets executed. If we have multiple
predecessors for the outer loop latch, it may be executed even if the inner
loop does not get executed.
This is a first step to support the case described in
https://bugs.llvm.org/show_bug.cgi?id=30472
Reviewers: efriedma, karthikthecool, mcrosier
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D43237
Added:
llvm/trunk/test/Transforms/LoopInterchange/lcssa.ll
Removed:
llvm/trunk/test/Transforms/LoopInterchange/current-limitations-lcssa.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp
llvm/trunk/test/Transforms/LoopInterchange/reductions.ll
Modified: llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp?rev=331037&r1=331036&r2=331037&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopInterchange.cpp Fri Apr 27 06:52:51 2018
@@ -543,10 +543,6 @@ struct LoopInterchange : public Function
printDepMatrix(DependencyMatrix);
#endif
- // Since we currently do not handle LCSSA PHI's any failure in loop
- // condition will now branch to LoopNestExit.
- // TODO: This should be removed once we handle LCSSA PHI nodes.
-
// Get the Outermost loop exit.
BasicBlock *LoopNestExit = OuterMostLoop->getExitBlock();
if (!LoopNestExit) {
@@ -554,12 +550,6 @@ struct LoopInterchange : public Function
return false;
}
- if (isa<PHINode>(LoopNestExit->begin())) {
- DEBUG(dbgs() << "PHI Nodes in loop nest exit is not handled for now "
- "since on failure all loops branch to loop nest exit.\n");
- return false;
- }
-
unsigned SelecLoopId = selectLoopForInterchange(LoopList);
// Move the selected loop outwards to the best possible position.
for (unsigned i = SelecLoopId; i > 0; i--) {
@@ -862,19 +852,6 @@ bool LoopInterchangeLegality::currentLim
}
// TODO: We only handle LCSSA PHI's corresponding to reduction for now.
- BasicBlock *OuterExit = OuterLoop->getExitBlock();
- if (!containsSafePHI(OuterExit, true)) {
- DEBUG(dbgs() << "Can only handle LCSSA PHIs in outer loops currently.\n");
- ORE->emit([&]() {
- return OptimizationRemarkMissed(DEBUG_TYPE, "NoLCSSAPHIOuter",
- OuterLoop->getStartLoc(),
- OuterLoop->getHeader())
- << "Only outer loops with LCSSA PHIs can be interchange "
- "currently.";
- });
- return true;
- }
-
BasicBlock *InnerExit = InnerLoop->getExitBlock();
if (!containsSafePHI(InnerExit, false)) {
DEBUG(dbgs() << "Can only handle LCSSA PHIs in inner loops currently.\n");
@@ -962,6 +939,43 @@ bool LoopInterchangeLegality::currentLim
return false;
}
+// We currently support LCSSA PHI nodes in the outer loop exit, if their
+// incoming values do not come from the outer loop latch or if the
+// outer loop latch has a single predecessor. In that case, the value will
+// be available if both the inner and outer loop conditions are true, which
+// will still be true after interchanging. If we have multiple predecessor,
+// that may not be the case, e.g. because the outer loop latch may be executed
+// if the inner loop is not executed.
+static bool areLoopExitPHIsSupported(Loop *OuterLoop, Loop *InnerLoop) {
+ BasicBlock *LoopNestExit = OuterLoop->getUniqueExitBlock();
+ for (PHINode &PHI : LoopNestExit->phis()) {
+ // FIXME: We currently are not able to detect floating point reductions
+ // and have to use floating point PHIs as a proxy to prevent
+ // interchanging in the presence of floating point reductions.
+ if (PHI.getType()->isFloatingPointTy())
+ return false;
+ for (unsigned i = 0; i < PHI.getNumIncomingValues(); i++) {
+ Instruction *IncomingI = dyn_cast<Instruction>(PHI.getIncomingValue(i));
+ if (!IncomingI || IncomingI->getParent() != OuterLoop->getLoopLatch())
+ continue;
+
+ // The incoming value is defined in the outer loop latch. Currently we
+ // only support that in case the outer loop latch has a single predecessor.
+ // This guarantees that the outer loop latch is executed if and only if
+ // the inner loop is executed (because tightlyNested() guarantees that the
+ // outer loop header only branches to the inner loop or the outer loop
+ // latch).
+ // FIXME: We could weaken this logic and allow multiple predecessors,
+ // if the values are produced outside the loop latch. We would need
+ // additional logic to update the PHI nodes in the exit block as
+ // well.
+ if (OuterLoop->getLoopLatch()->getUniquePredecessor() == nullptr)
+ return false;
+ }
+ }
+ return true;
+}
+
bool LoopInterchangeLegality::canInterchangeLoops(unsigned InnerLoopId,
unsigned OuterLoopId,
CharMatrix &DepMatrix) {
@@ -1037,6 +1051,17 @@ bool LoopInterchangeLegality::canInterch
});
return false;
}
+
+ if (!areLoopExitPHIsSupported(OuterLoop, InnerLoop)) {
+ DEBUG(dbgs() << "Found unsupported PHI nodes in outer loop exit.\n");
+ ORE->emit([&]() {
+ return OptimizationRemarkMissed(DEBUG_TYPE, "UnsupportedExitPHI",
+ OuterLoop->getStartLoc(),
+ OuterLoop->getHeader())
+ << "Found unsupported PHI node in loop exit.";
+ });
+ return false;
+ }
return true;
}
Removed: llvm/trunk/test/Transforms/LoopInterchange/current-limitations-lcssa.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopInterchange/current-limitations-lcssa.ll?rev=331036&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopInterchange/current-limitations-lcssa.ll (original)
+++ llvm/trunk/test/Transforms/LoopInterchange/current-limitations-lcssa.ll (removed)
@@ -1,70 +0,0 @@
-; REQUIRES: asserts
-; RUN: opt < %s -basicaa -loop-interchange -S -debug 2>&1 | FileCheck %s
-
-target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
-target triple = "x86_64-unknown-linux-gnu"
-
- at A = common global [100 x [100 x i32]] zeroinitializer
- at C = common global [100 x [100 x i32]] zeroinitializer
-
-;; FIXME:
-;; Test for interchange when we have an lcssa phi. This should ideally be interchanged but it is currently not supported.
-;; for(gi=1;gi<N;gi++)
-;; for(gj=1;gj<M;gj++)
-;; A[gj][gi] = A[gj - 1][gi] + C[gj][gi];
-
-; CHECK: PHI Nodes in loop nest exit is not handled for now since on failure all loops branch to loop nest exit.
-
- at gi = common global i32 0
- at gj = common global i32 0
-
-define void @interchange_07(i32 %N, i32 %M){
-entry:
- store i32 1, i32* @gi
- %cmp21 = icmp sgt i32 %N, 1
- br i1 %cmp21, label %for.cond1.preheader.lr.ph, label %for.end16
-
-for.cond1.preheader.lr.ph:
- %cmp218 = icmp sgt i32 %M, 1
- %gi.promoted = load i32, i32* @gi
- %0 = add i32 %M, -1
- %1 = sext i32 %gi.promoted to i64
- %2 = sext i32 %N to i64
- %3 = add i32 %gi.promoted, 1
- %4 = icmp slt i32 %3, %N
- %smax = select i1 %4, i32 %N, i32 %3
- br label %for.cond1.preheader
-
-for.cond1.preheader:
- %indvars.iv25 = phi i64 [ %1, %for.cond1.preheader.lr.ph ], [ %indvars.iv.next26, %for.inc14 ]
- br i1 %cmp218, label %for.body3, label %for.inc14
-
-for.body3:
- %indvars.iv = phi i64 [ %indvars.iv.next, %for.body3 ], [ 1, %for.cond1.preheader ]
- %5 = add nsw i64 %indvars.iv, -1
- %arrayidx5 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %5, i64 %indvars.iv25
- %6 = load i32, i32* %arrayidx5
- %arrayidx9 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @C, i64 0, i64 %indvars.iv, i64 %indvars.iv25
- %7 = load i32, i32* %arrayidx9
- %add = add nsw i32 %7, %6
- %arrayidx13 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %indvars.iv, i64 %indvars.iv25
- store i32 %add, i32* %arrayidx13
- %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
- %lftr.wideiv = trunc i64 %indvars.iv to i32
- %exitcond = icmp eq i32 %lftr.wideiv, %0
- br i1 %exitcond, label %for.inc14, label %for.body3
-
-for.inc14:
- %inc.lcssa23 = phi i32 [ 1, %for.cond1.preheader ], [ %M, %for.body3 ]
- %indvars.iv.next26 = add nsw i64 %indvars.iv25, 1
- %cmp = icmp slt i64 %indvars.iv.next26, %2
- br i1 %cmp, label %for.cond1.preheader, label %for.cond.for.end16_crit_edge
-
-for.cond.for.end16_crit_edge:
- store i32 %inc.lcssa23, i32* @gj
- store i32 %smax, i32* @gi
- br label %for.end16
-
-for.end16:
- ret void
-}
Added: llvm/trunk/test/Transforms/LoopInterchange/lcssa.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopInterchange/lcssa.ll?rev=331037&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopInterchange/lcssa.ll (added)
+++ llvm/trunk/test/Transforms/LoopInterchange/lcssa.ll Fri Apr 27 06:52:51 2018
@@ -0,0 +1,171 @@
+; RUN: opt < %s -basicaa -loop-interchange -pass-remarks-missed='loop-interchange' -pass-remarks-output=%t
+; RUN: cat %t | FileCheck --check-prefix REMARK %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+ at A = common global [100 x [100 x i32]] zeroinitializer
+ at C = common global [100 x [100 x i32]] zeroinitializer
+ at X = common global i32 0
+ at Y = common global i64 0
+ at F = common global float 0.0
+
+; We cannot interchange this loop at the moment, because iv.outer.next is
+; produced in the outer loop latch and used in the loop exit block. If the inner
+; loop body is not executed, the outer loop latch won't be executed either
+; after interchanging.
+; REMARK: UnsupportedExitPHI
+; REMARK-NEXT: lcssa_01
+
+define void @lcssa_01(){
+entry:
+ %cmp21 = icmp sgt i64 100, 1
+ br i1 %cmp21, label %outer.ph, label %for.end16
+
+outer.ph:
+ %cmp218 = icmp sgt i64 100, 1
+ br label %outer.header
+
+outer.header:
+ %iv.outer= phi i64 [ 1, %outer.ph ], [ %iv.outer.next, %outer.inc ]
+ br i1 %cmp218, label %for.body3, label %outer.inc
+
+for.body3:
+ %iv.inner = phi i64 [ %iv.inner.next, %for.body3 ], [ 1, %outer.header ]
+ %arrayidx5 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %iv.inner, i64 %iv.outer
+ %vA = load i32, i32* %arrayidx5
+ %arrayidx9 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @C, i64 0, i64 %iv.inner, i64 %iv.outer
+ %vC = load i32, i32* %arrayidx9
+ %add = add nsw i32 %vA, %vC
+ store i32 %add, i32* %arrayidx5
+ %iv.inner.next = add nuw nsw i64 %iv.inner, 1
+ %exitcond = icmp eq i64 %iv.inner.next, 100
+ br i1 %exitcond, label %outer.inc, label %for.body3
+
+outer.inc:
+ %iv.outer.next = add nsw i64 %iv.outer, 1
+ %cmp = icmp eq i64 %iv.outer.next, 100
+ br i1 %cmp, label %outer.header, label %for.exit
+
+for.exit:
+ store i64 %iv.outer.next, i64 * @Y
+ br label %for.end16
+
+for.end16:
+ ret void
+}
+
+; REMARK: UnsupportedExitPHI
+; REMARK-NEXT: lcssa_02
+define void @lcssa_02(){
+entry:
+ %cmp21 = icmp sgt i64 100, 1
+ br i1 %cmp21, label %outer.ph, label %for.end16
+
+outer.ph:
+ %cmp218 = icmp sgt i64 100, 1
+ br label %outer.header
+
+outer.header:
+ %iv.outer= phi i64 [ 1, %outer.ph ], [ %iv.outer.next, %outer.inc ]
+ br i1 %cmp218, label %for.body3, label %outer.inc
+
+for.body3:
+ %iv.inner = phi i64 [ %iv.inner.next, %for.body3 ], [ 1, %outer.header ]
+ %arrayidx5 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %iv.inner, i64 %iv.outer
+ %vA = load i32, i32* %arrayidx5
+ %arrayidx9 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @C, i64 0, i64 %iv.inner, i64 %iv.outer
+ %vC = load i32, i32* %arrayidx9
+ %add = add nsw i32 %vA, %vC
+ store i32 %add, i32* %arrayidx5
+ %iv.inner.next = add nuw nsw i64 %iv.inner, 1
+ %exitcond = icmp eq i64 %iv.inner.next, 100
+ br i1 %exitcond, label %outer.inc, label %for.body3
+
+outer.inc:
+ %iv.inner.end = phi i64 [ 0, %outer.header ], [ %iv.inner.next, %for.body3 ]
+ %iv.outer.next = add nsw i64 %iv.outer, 1
+ %cmp = icmp eq i64 %iv.outer.next, 100
+ br i1 %cmp, label %outer.header, label %for.exit
+
+for.exit:
+ store i64 %iv.inner.end, i64 * @Y
+ br label %for.end16
+
+for.end16:
+ ret void
+}
+
+
+; REMARK: Interchanged
+; REMARK-NEXT: lcssa_03
+define void @lcssa_03(){
+entry:
+ br label %outer.header
+
+outer.header:
+ %iv.outer= phi i64 [ 1, %entry ], [ %iv.outer.next, %outer.inc ]
+ br label %for.body3
+
+for.body3:
+ %iv.inner = phi i64 [ %iv.inner.next, %for.body3 ], [ 1, %outer.header ]
+ %arrayidx5 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %iv.inner, i64 %iv.outer
+ %vA = load i32, i32* %arrayidx5
+ %arrayidx9 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @C, i64 0, i64 %iv.inner, i64 %iv.outer
+ %vC = load i32, i32* %arrayidx9
+ %add = add nsw i32 %vA, %vC
+ store i32 %add, i32* %arrayidx5
+ %iv.inner.next = add nuw nsw i64 %iv.inner, 1
+ %exitcond = icmp eq i64 %iv.inner.next, 100
+ br i1 %exitcond, label %outer.inc, label %for.body3
+
+outer.inc:
+ %iv.outer.next = add nsw i64 %iv.outer, 1
+ %cmp = icmp eq i64 %iv.outer.next, 100
+ br i1 %cmp, label %outer.header, label %for.exit
+
+for.exit:
+ store i64 %iv.inner, i64 * @Y
+ br label %for.end16
+
+for.end16:
+ ret void
+}
+
+; FIXME: We currently do not support LCSSA phi nodes involving floating point
+; types, as we fail to detect floating point reductions for now.
+; REMARK: UnsupportedPHIOuter
+; REMARK-NEXT: lcssa_04
+define void @lcssa_04(){
+entry:
+ br label %outer.header
+
+outer.header:
+ %iv.outer= phi i64 [ 1, %entry ], [ %iv.outer.next, %outer.inc ]
+ %float.outer= phi float [ 1.0, %entry ], [ 2.0, %outer.inc ]
+ br label %for.body3
+
+for.body3:
+ %iv.inner = phi i64 [ %iv.inner.next, %for.body3 ], [ 1, %outer.header ]
+ %arrayidx5 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @A, i64 0, i64 %iv.inner, i64 %iv.outer
+ %vA = load i32, i32* %arrayidx5
+ %arrayidx9 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* @C, i64 0, i64 %iv.inner, i64 %iv.outer
+ %vC = load i32, i32* %arrayidx9
+ %add = add nsw i32 %vA, %vC
+ store i32 %add, i32* %arrayidx5
+ %iv.inner.next = add nuw nsw i64 %iv.inner, 1
+ %exitcond = icmp eq i64 %iv.inner.next, 100
+ br i1 %exitcond, label %outer.inc, label %for.body3
+
+outer.inc:
+ %iv.outer.next = add nsw i64 %iv.outer, 1
+ %cmp = icmp eq i64 %iv.outer.next, 100
+ br i1 %cmp, label %outer.header, label %for.exit
+
+for.exit:
+ store float %float.outer, float* @F
+ br label %for.end16
+
+for.end16:
+ ret void
+}
Modified: llvm/trunk/test/Transforms/LoopInterchange/reductions.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopInterchange/reductions.ll?rev=331037&r1=331036&r2=331037&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopInterchange/reductions.ll (original)
+++ llvm/trunk/test/Transforms/LoopInterchange/reductions.ll Fri Apr 27 06:52:51 2018
@@ -220,3 +220,43 @@ for.inc13:
for.end15: ; preds = %for.inc13, %entry
ret void
}
+
+;; for( int i=1;i<N;i++)
+;; for( int j=1;j<N;j++)
+;; X+=A[j][i];
+;; Y = X
+; CHECK: Loops interchanged.
+define void @reduction_05(i32 %N) {
+entry:
+ %cmp16 = icmp sgt i32 %N, 1
+ br i1 %cmp16, label %for.body7.lr.ph, label %for.end8
+
+for.body7.lr.ph: ; preds = %entry, %for.cond1.for.inc6_crit_edge
+ %indvars.iv18 = phi i64 [ %indvars.iv.next19, %for.cond1.for.inc6_crit_edge ], [ 1, %entry ]
+ %X.promoted = load i32, i32* @X
+ br label %for.body7
+
+for.body7: ; preds = %for.body7, %for.body7.lr.ph
+ %indvars.iv = phi i64 [ 1, %for.body7.lr.ph ], [ %indvars.iv.next, %for.body7 ]
+ %add15 = phi i32 [ %X.promoted, %for.body7.lr.ph ], [ %add, %for.body7 ]
+ %arrayidx5 = getelementptr inbounds [500 x [500 x i32]], [500 x [500 x i32]]* @A, i64 0, i64 %indvars.iv, i64 %indvars.iv18
+ %0 = load i32, i32* %arrayidx5
+ %add = add nsw i32 %add15, %0
+ %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.cond1.for.inc6_crit_edge, label %for.body7
+
+for.cond1.for.inc6_crit_edge: ; preds = %for.body7
+ store i32 %add, i32* @X
+ %indvars.iv.next19 = add nuw nsw i64 %indvars.iv18, 1
+ %lftr.wideiv20 = trunc i64 %indvars.iv.next19 to i32
+ %exitcond21 = icmp eq i32 %lftr.wideiv20, %N
+ br i1 %exitcond21, label %for.end8, label %for.body7.lr.ph
+
+for.end8: ; preds = %for.cond1.for.inc6_crit_edge, %entry
+ %add.res = phi i32 [ %add, %for.cond1.for.inc6_crit_edge], [ 0, %entry ]
+ store i32 %add.res, i32* @Y
+
+ ret void
+}
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