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[IndVars] Preserve LCSSA in eliminateIdentitySCEV

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Summary:
After r249211, SCEV can see through some LCSSA phis.  Add a
`replacementPreservesLCSSAForm` check before replacing uses of these phi
nodes with a simplified use of the induction variable to avoid breaking
LCSSA.

Fixes 25047.

Depends on D13460.

Reviewers: atrick, hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13461

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249575 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das 2015-10-07 17:38:31 +00:00
parent 655d66e1fe
commit d23e55c402
2 changed files with 52 additions and 0 deletions
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3
lib/Transforms/Utils/SimplifyIndVar.cpp
View File

@ -333,6 +333,9 @@ bool SimplifyIndvar::eliminateIdentitySCEV(Instruction *UseInst,
if (!DT || !DT->dominates(IVOperand, UseInst))
return false;
if (!LI->replacementPreservesLCSSAForm(UseInst, IVOperand))
return false;
DEBUG(dbgs() << "INDVARS: Eliminated identity: " << *UseInst << '\n');
UseInst->replaceAllUsesWith(IVOperand);

49
test/Transforms/IndVarSimplify/pr25047.ll Normal file
View File

@ -0,0 +1,49 @@
; RUN: opt -indvars -S < %s | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.11.0"
define void @fn1(i1 %c0, i1 %c1) {
; CHECK-LABEL: @fn1(
entry:
br i1 %c0, label %for.end.34, label %for.cond.1thread-pre-split
for.cond.loopexit: ; preds = %for.end.29, %for.end.7
%f.lcssa = phi i32 [ %f.1, %for.end.29 ], [ %f.1, %for.end.7 ]
br i1 %c1, label %for.end.34, label %for.cond.1thread-pre-split
for.cond.1thread-pre-split: ; preds = %for.cond.loopexit, %entry
%f.047 = phi i32 [ %f.lcssa, %for.cond.loopexit ], [ 0, %entry ]
br label %for.cond.1
for.cond.1: ; preds = %for.cond.1, %for.cond.1thread-pre-split
br i1 %c1, label %for.cond.4, label %for.cond.1
for.cond.4: ; preds = %for.end.29, %for.cond.1
%f.1 = phi i32 [ 0, %for.end.29 ], [ %f.047, %for.cond.1 ]
br label %for.cond.5
for.cond.5: ; preds = %for.cond.5, %for.cond.4
%h.0 = phi i32 [ 0, %for.cond.4 ], [ %inc, %for.cond.5 ]
%cmp = icmp slt i32 %h.0, 1
%inc = add nsw i32 %h.0, 1
br i1 %cmp, label %for.cond.5, label %for.end.7
for.end.7: ; preds = %for.cond.5
%g.lcssa = phi i32 [ %h.0, %for.cond.5 ]
%tobool10 = icmp eq i32 %g.lcssa, 0
br i1 %tobool10, label %for.end.8, label %for.cond.loopexit
for.end.8: ; preds = %for.end.7
br i1 %c1, label %for.cond.19, label %for.end.29
for.cond.19: ; preds = %for.cond.19, %for.end.8
br label %for.cond.19
for.end.29: ; preds = %for.end.8
%tobool30 = icmp eq i32 %f.1, 0
br i1 %tobool30, label %for.cond.4, label %for.cond.loopexit
for.end.34: ; preds = %for.cond.loopexit, %entry
ret void
}