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SimplifyCFG: Add Trunc, ZExt and SExt to the list of cheap instructions for phi node folding

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130526 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Peter Collingbourne 2011-04-29 18:47:25 +00:00
parent c8497b6a25
commit 8a70192b51
2 changed files with 12 additions and 6 deletions
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3
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -261,6 +261,9 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB,
case Instruction::LShr:
case Instruction::AShr:
case Instruction::ICmp:
case Instruction::Trunc:
case Instruction::ZExt:
case Instruction::SExt:
break; // These are all cheap and non-trapping instructions.
}

15
test/Transforms/SimplifyCFG/PhiEliminate2.ll
View File

@ -1,14 +1,17 @@
; RUN: opt < %s -simplifycfg -S | not grep br
define i32 @test(i1 %C, i32 %V1, i32 %V2) {
define i32 @test(i1 %C, i32 %V1, i32 %V2, i16 %V3) {
entry:
br i1 %C, label %then, label %Cont
br i1 %C, label %then, label %else
then: ; preds = %entry
%V3 = or i32 %V2, %V1 ; <i32> [#uses=1]
%V4 = or i32 %V2, %V1 ; <i32> [#uses=1]
br label %Cont
Cont: ; preds = %then, %entry
%V4 = phi i32 [ %V1, %entry ], [ %V3, %then ] ; <i32> [#uses=0]
call i32 @test( i1 false, i32 0, i32 0 ) ; <i32>:0 [#uses=0]
else: ; preds = %entry
%V5 = sext i16 %V3 to i32 ; <i32> [#uses=1]
br label %Cont
Cont: ; preds = %then, %else
%V6 = phi i32 [ %V5, %else ], [ %V4, %then ] ; <i32> [#uses=0]
call i32 @test( i1 false, i32 0, i32 0, i16 0 ) ; <i32>:0 [#uses=0]
ret i32 %V1
}