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[LoopDeletion] Forget loop before setting values to undef

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After D71539, we need to forget the loop before setting the incoming
values of phi nodes in exit blocks, because we are looking through those
phi nodes now and the SCEV expression could depend on the loop phi. If
we update the phi nodes before forgetting the loop, we miss those users
during invalidation.

Reviewed By: reames

Differential Revision: https://reviews.llvm.org/D88167
This commit is contained in:
Florian Hahn
2020-09-29 10:38:44 +01:00
parent 9100bd772d
commit 60b852092c
3 changed files with 120 additions and 1 deletions
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4
llvm/lib/Transforms/Scalar/LoopDeletion.cpp
View File

@@ -165,6 +165,10 @@ static LoopDeletionResult deleteLoopIfDead(Loop *L, DominatorTree &DT,
if (ExitBlock && isLoopNeverExecuted(L)) {
LLVM_DEBUG(dbgs() << "Loop is proven to never execute, delete it!");
// We need to forget the loop before setting the incoming values of the exit
// phis to undef, so we properly invalidate the SCEV expressions for those
// phis.
SE.forgetLoop(L);
// Set incoming value to undef for phi nodes in the exit block.
for (PHINode &P : ExitBlock->phis()) {
std::fill(P.incoming_values().begin(), P.incoming_values().end(),

3
llvm/lib/Transforms/Utils/LoopUtils.cpp
View File

@@ -724,6 +724,9 @@ void llvm::deleteDeadLoop(Loop *L, DominatorTree *DT, ScalarEvolution *SE,
}
LI->destroy(L);
}
if (SE)
SE->verify();
}
/// Checks if \p L has single exit through latch block except possibly

114
llvm/test/Transforms/LoopDeletion/update-scev.ll
View File

@@ -1,4 +1,4 @@
; RUN: opt -S -analyze -scalar-evolution -loop-deletion -scalar-evolution < %s | FileCheck %s --check-prefix=SCEV-EXPRS
; RUN: opt -S -analyze -scalar-evolution -loop-deletion -scalar-evolution -verify-scev < %s | FileCheck %s --check-prefix=SCEV-EXPRS
; RUN: opt -S -loop-deletion < %s | FileCheck %s --check-prefix=IR-AFTER-TRANSFORM
; RUN: opt -S -indvars -loop-deletion -indvars < %s | FileCheck %s --check-prefix=ORIGINAL-CRASH
@@ -54,3 +54,115 @@ for.inc11: ; preds = %for.body6
for.cond14: ; preds = %for.cond14, %for.inc11
br i1 undef, label %for.cond, label %for.cond14
}
; LoopDeletion removes the loop %for.body7.1. Make sure %inc.lcssa.1 in the loop
; exit block is correctly invalidated.
define void @test2(double* %bx, i64 %by) local_unnamed_addr align 2 {
; IR-AFTER-TRANSFORM-LABEL: @test2(
; IR-AFTER-TRANSFORM-NOT: for.body7.1:
; SCEV-EXPRS-LABEL: test2
; SCEV-EXPRS: %inc.lcssa.1 = phi i64 [ undef, %for.body7.preheader.1 ]
; SCEV-EXPRS-NEXT: --> undef
entry:
%cmp = icmp sgt i64 %by, 0
br label %for.cond.preheader
for.cond.preheader: ; preds = %entry
br i1 %cmp, label %for.cond5.preheader.lr.ph, label %for.end14
for.cond5.preheader.lr.ph: ; preds = %for.cond.preheader
br label %for.cond5.preheader
for.cond.loopexit.loopexit: ; preds = %for.body10
%inc11.lcssa = phi i64 [ %inc11, %for.body10 ]
br label %for.cond.loopexit
for.cond.loopexit: ; preds = %for.cond8.preheader, %for.cond.loopexit.loopexit
%ca.3.lcssa = phi i64 [ %ca.2.lcssa, %for.cond8.preheader ], [ %inc11.lcssa, %for.cond.loopexit.loopexit ]
br i1 %cmp, label %for.cond5.preheader, label %for.end14.loopexit
for.cond5.preheader: ; preds = %for.cond.loopexit, %for.cond5.preheader.lr.ph
%ca.19 = phi i64 [ 0, %for.cond5.preheader.lr.ph ], [ %ca.3.lcssa, %for.cond.loopexit ]
br i1 false, label %for.cond8.preheader, label %for.body7.preheader
for.body7.preheader: ; preds = %for.cond5.preheader
br label %for.body7
for.cond8.preheader.loopexit: ; preds = %for.body7
%inc.lcssa = phi i64 [ %inc, %for.body7 ]
br label %for.cond8.preheader
for.cond8.preheader: ; preds = %for.cond8.preheader.loopexit, %for.cond5.preheader
%ca.2.lcssa = phi i64 [ %ca.19, %for.cond5.preheader ], [ %inc.lcssa, %for.cond8.preheader.loopexit ]
br i1 true, label %for.body10.preheader, label %for.cond.loopexit
for.body10.preheader: ; preds = %for.cond8.preheader
br label %for.body10
for.body7: ; preds = %for.body7, %for.body7.preheader
%ca.26 = phi i64 [ %inc, %for.body7 ], [ %ca.19, %for.body7.preheader ]
%inc = add nsw i64 %ca.26, 1
%arrayidx = getelementptr inbounds double, double* %bx, i64 %ca.26
store double 0.000000e+00, double* %arrayidx, align 8
br i1 false, label %for.cond8.preheader.loopexit, label %for.body7
for.body10: ; preds = %for.body10, %for.body10.preheader
%ca.37 = phi i64 [ %inc11, %for.body10 ], [ %ca.2.lcssa, %for.body10.preheader ]
%inc11 = add nsw i64 %ca.37, 1
br i1 true, label %for.body10, label %for.cond.loopexit.loopexit
for.end14.loopexit: ; preds = %for.cond.loopexit
br label %for.end14
for.end14: ; preds = %for.end14.loopexit, %for.cond.preheader
br i1 %cmp, label %for.cond5.preheader.lr.ph.1, label %for.end14.1
for.cond5.preheader.lr.ph.1: ; preds = %for.end14
br label %for.cond5.preheader.1
for.cond5.preheader.1: ; preds = %for.cond.loopexit.1, %for.cond5.preheader.lr.ph.1
%ca.19.1 = phi i64 [ 0, %for.cond5.preheader.lr.ph.1 ], [ %ca.3.lcssa.1, %for.cond.loopexit.1 ]
br i1 true, label %for.cond8.preheader.1, label %for.body7.preheader.1
for.body7.preheader.1: ; preds = %for.cond5.preheader.1
br label %for.body7.1
for.body7.1: ; preds = %for.body7.1, %for.body7.preheader.1
%ca.26.1 = phi i64 [ %inc.1, %for.body7.1 ], [ %ca.19.1, %for.body7.preheader.1 ]
%inc.1 = add nsw i64 %ca.26.1, 1
%arrayidx.1 = getelementptr inbounds double, double* %bx, i64 %ca.26.1
store double 0.000000e+00, double* %arrayidx.1, align 8
br i1 true, label %for.cond8.preheader.loopexit.1, label %for.body7.1
for.cond8.preheader.loopexit.1: ; preds = %for.body7.1
%inc.lcssa.1 = phi i64 [ %inc.1, %for.body7.1 ]
br label %for.cond8.preheader.1
for.cond8.preheader.1: ; preds = %for.cond8.preheader.loopexit.1, %for.cond5.preheader.1
%ca.2.lcssa.1 = phi i64 [ %ca.19.1, %for.cond5.preheader.1 ], [ %inc.lcssa.1, %for.cond8.preheader.loopexit.1 ]
br i1 false, label %for.body10.preheader.1, label %for.cond.loopexit.1
for.body10.preheader.1: ; preds = %for.cond8.preheader.1
br label %for.body10.1
for.body10.1: ; preds = %for.body10.1, %for.body10.preheader.1
%ca.37.1 = phi i64 [ %inc11.1, %for.body10.1 ], [ %ca.2.lcssa.1, %for.body10.preheader.1 ]
%inc11.1 = add nsw i64 %ca.37.1, 1
br i1 false, label %for.body10.1, label %for.cond.loopexit.loopexit.1
for.cond.loopexit.loopexit.1: ; preds = %for.body10.1
%inc11.lcssa.1 = phi i64 [ %inc11.1, %for.body10.1 ]
br label %for.cond.loopexit.1
for.cond.loopexit.1: ; preds = %for.cond.loopexit.loopexit.1, %for.cond8.preheader.1
%ca.3.lcssa.1 = phi i64 [ %ca.2.lcssa.1, %for.cond8.preheader.1 ], [ %inc11.lcssa.1, %for.cond.loopexit.loopexit.1 ]
br i1 %cmp, label %for.cond5.preheader.1, label %for.end14.loopexit.1
for.end14.loopexit.1: ; preds = %for.cond.loopexit.1
br label %for.end14.1
for.end14.1: ; preds = %for.end14.loopexit.1, %for.end14
ret void
}