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[IndVars] Fix PR26974: make sure replaceCongruentIVs doesn't break LCSSA

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Summary:
replaceCongruentIVs can break LCSSA when trying to replace IV increments
since it tries to replace all uses of a phi node with another phi node
while both of the phi nodes are not necessarily in the processed loop.
This will cause an assert in IndVars.

To fix this, we add a check to make sure that the replacement maintains
LCSSA.

Reviewers: sanjoy

Subscribers: mzolotukhin, llvm-commits

Differential Revision: http://reviews.llvm.org/D18266

llvm-svn: 263941
This commit is contained in:
Silviu Baranga 2016-03-21 12:44:29 +00:00
parent 7184969f04
commit d4c3c35f5f
2 changed files with 61 additions and 0 deletions
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1
lib/Analysis/ScalarEvolutionExpander.cpp
View File

@ -1820,6 +1820,7 @@ unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
IsomorphicInc->getType());
if (OrigInc != IsomorphicInc
&& TruncExpr == SE.getSCEV(IsomorphicInc)
&& SE.LI.replacementPreservesLCSSAForm(IsomorphicInc, OrigInc)
&& ((isa<PHINode>(OrigInc) && isa<PHINode>(IsomorphicInc))
|| hoistIVInc(OrigInc, IsomorphicInc))) {
DEBUG_WITH_TYPE(DebugType, dbgs()

60
test/Transforms/IndVarSimplify/pr26974.ll Normal file
View File

@ -0,0 +1,60 @@
; RUN: opt -indvars -S < %s | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
; indvars will try to replace %b.0.lcssa with %t.1. If it does this,
; it will break LCSSA.
@c = external global i32, align 4
; CHECK-LABEL: @fn1
define void @fn1() {
entry:
br label %for.body
for.cond1.preheader: ; preds = %for.body
%0 = load i32, i32* @c, align 4
br i1 undef, label %for.cond1.us.preheader, label %for.cond1
for.cond1.us.preheader: ; preds = %for.cond1.preheader
br label %for.cond1.us
for.cond1.us: ; preds = %for.cond1.us, %for.cond1.us.preheader
br label %for.cond1.us
for.body: ; preds = %for.body, %entry
br i1 undef, label %for.body, label %for.cond1.preheader
for.cond1: ; preds = %for.cond1.preheader
br i1 true, label %for.body9.lr.ph, label %for.cond13.preheader
for.body9.lr.ph: ; preds = %for.cond1
br i1 undef, label %for.body9.us.preheader, label %for.body9
for.body9.us.preheader: ; preds = %for.body9.lr.ph
br label %for.body9.us
for.body9.us: ; preds = %for.body9.us, %for.body9.us.preheader
br label %for.body9.us
for.cond13.preheader: ; preds = %for.body9, %for.cond1
%b.0.lcssa = phi i32 [ %0, %for.body9 ], [ 0, %for.cond1 ]
br label %for.cond13
for.body9: ; preds = %for.body9.lr.ph
br label %for.cond13.preheader
for.cond13: ; preds = %for.cond13, %for.cond13.preheader
%d.1 = phi i32 [ %t.1, %for.cond13 ], [ %0, %for.cond13.preheader ]
%t.1 = phi i32 [ %b.0.lcssa, %for.cond13 ], [ %0, %for.cond13.preheader ]
br i1 undef, label %for.cond18.preheader, label %for.cond13
for.cond18.preheader: ; preds = %for.cond13
br label %for.cond18
for.cond18: ; preds = %for.cond18, %for.cond18.preheader
%b.1 = phi i32 [ %xor, %for.cond18 ], [ %b.0.lcssa, %for.cond18.preheader ]
%add = add nsw i32 %b.1, %d.1
%xor = xor i32 %add, %b.1
br label %for.cond18
}