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Do not hoist instruction above branch condition. The instruction may use branch condition.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56286 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel
2008-09-17 18:21:49 +00:00
parent 00622952ce
commit 48fbc2d39b
2 changed files with 20 additions and 9 deletions
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11
lib/Transforms/Utils/SimplifyCFG.cpp
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@@ -1046,15 +1046,8 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
return false; return false;
} }
// If we get here, we can hoist the instruction. Try to place it before the // If we get here, we can hoist the instruction.
// icmp instruction preceeding the conditional branch. BIParent->getInstList().splice(BI, BB1->getInstList(), I);
BasicBlock::iterator InsertPos = BI;
if (InsertPos != BIParent->begin())
--InsertPos;
if (InsertPos == BrCond && !isa<PHINode>(BrCond))
BIParent->getInstList().splice(InsertPos, BB1->getInstList(), I);
else
BIParent->getInstList().splice(BI, BB1->getInstList(), I);
// Create a select whose true value is the speculatively executed value and // Create a select whose true value is the speculatively executed value and
// false value is the previously determined FalseV. // false value is the previously determined FalseV.

18
test/Transforms/SimplifyCFG/2008-09-17-SpeculativeHoist.ll Normal file
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@@ -0,0 +1,18 @@
; RUN: llvm-as < %s | opt -simplifycfg -disable-output
; PR 2800
define void @foo() {
start:
%tmp = call i1 @bar( ) ; <i1> [#uses=4]
br i1 %tmp, label %brtrue, label %brfalse
brtrue: ; preds = %start
%tmpnew = and i1 %tmp, %tmp ; <i1> [#uses=1]
br label %brfalse
brfalse: ; preds = %brtrue, %start
%andandtmp.0 = phi i1 [ %tmp, %start ], [ %tmpnew, %brtrue ] ; <i1> [#uses=0]
ret void
}
declare i1 @bar()