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Teach simplifycfg that setcc is cheap and non-trapping, so that it can

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convert this:

        %tmp.1 = seteq int %i, 0                ; <bool> [#uses=1]
        br bool %tmp.1, label %shortcirc_done, label %shortcirc_next

shortcirc_next:         ; preds = %entry
        %tmp.4 = seteq int %j, 0                ; <bool> [#uses=1]
        br label %shortcirc_done

shortcirc_done:         ; preds = %shortcirc_next, %entry
        %shortcirc_val = phi bool [ %tmp.4, %shortcirc_next ], [ true, %entry ]         ; <bool> [#uses=1]

to this:
        %tmp.1 = seteq int %i, 0                ; <bool> [#uses=1]
        %tmp.4 = seteq int %j, 0                ; <bool> [#uses=1]
        %shortcirc_val = select bool %tmp.1, bool true, bool %tmp.4             ; <bool> [#uses=1]

... which is later simplified by instcombine into an or.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21388 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-04-21 05:31:13 +00:00
parent 01d7139f93
commit bf5d4fb7d8
1 changed files with 6 additions and 0 deletions
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6
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -232,6 +232,12 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB,
case Instruction::Xor:
case Instruction::Shl:
case Instruction::Shr:
case Instruction::SetEQ:
case Instruction::SetNE:
case Instruction::SetLT:
case Instruction::SetGT:
case Instruction::SetLE:
case Instruction::SetGE:
break; // These are all cheap and non-trapping instructions.
}