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[SCEV] Pick backedge values for phi nodes correctly
Summary: `getConstantEvolutionLoopExitValue` and `ComputeExitCountExhaustively` assumed all phi nodes in the loop header have the same order of incoming values. This is not correct, and this commit changes `getConstantEvolutionLoopExitValue` and `ComputeExitCountExhaustively` to lookup the backedge value of a phi node using the loop's latch block. Unfortunately, there is still some code duplication `getConstantEvolutionLoopExitValue` and `ComputeExitCountExhaustively`. At some point in the future we should extract out a helper class / method that can evolve constant evolution phi nodes across iterations. Fixes 25060. Thanks to Mattias Eriksson for the spot-on analysis! Depends on D13457. Reviewers: atrick, hfinkel Subscribers: materi, llvm-commits Differential Revision: http://reviews.llvm.org/D13458 llvm-svn: 249712
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,37 @@ | ||
; RUN: opt -S -indvars < %s | FileCheck %s | ||
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define i16 @fn1() { | ||
; CHECK-LABEL: @fn1( | ||
entry: | ||
br label %bb1 | ||
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bb1: | ||
%i = phi i16 [ 0, %entry ], [ 1, %bb1 ] | ||
%storemerge = phi i16 [ %storemerge2, %bb1 ], [ 0, %entry ] | ||
%storemerge2 = phi i16 [ 10, %entry ], [ 200, %bb1 ] | ||
%tmp10 = icmp eq i16 %i, 1 | ||
br i1 %tmp10, label %bb5, label %bb1 | ||
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bb5: | ||
%storemerge.lcssa = phi i16 [ %storemerge, %bb1 ] | ||
; CHECK: ret i16 10 | ||
ret i16 %storemerge.lcssa | ||
} | ||
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define i16 @fn2() { | ||
; CHECK-LABEL: @fn2( | ||
entry: | ||
br label %bb1 | ||
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bb1: | ||
%canary = phi i16 [ 0, %entry ], [ %canary.inc, %bb1 ] | ||
%i = phi i16 [ 0, %entry ], [ %storemerge, %bb1 ] | ||
%storemerge = phi i16 [ 0, %bb1 ], [ 10, %entry ] | ||
%canary.inc = add i16 %canary, 1 | ||
%_tmp10 = icmp eq i16 %i, 10 | ||
br i1 %_tmp10, label %bb5, label %bb1 | ||
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bb5: | ||
; CHECK: ret i16 1 | ||
ret i16 %canary | ||
} |