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Check to see if a two-entry PHI block can be simplified

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before trying to merge the block into its predecessors.
This allows two-entry-phi-return.ll to be simplified
into a single basic block.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48252 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2008-03-11 21:53:06 +00:00
parent a8ab8938a7
commit 882d87d168
2 changed files with 21 additions and 6 deletions
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12
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -1224,6 +1224,12 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
// away...
Changed |= ConstantFoldTerminator(BB);
// If there is a trivial two-entry PHI node in this basic block, and we can
// eliminate it, do so now.
if (PHINode *PN = dyn_cast<PHINode>(BB->begin()))
if (PN->getNumIncomingValues() == 2)
Changed |= FoldTwoEntryPHINode(PN);
// If this is a returning block with only PHI nodes in it, fold the return
// instruction into any unconditional branch predecessors.
//
@ -1915,11 +1921,5 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
}
}
// If there is a trivial two-entry PHI node in this basic block, and we can
// eliminate it, do so now.
if (PHINode *PN = dyn_cast<PHINode>(BB->begin()))
if (PN->getNumIncomingValues() == 2)
Changed |= FoldTwoEntryPHINode(PN);
return Changed;
}

15
test/Transforms/SimplifyCFG/two-entry-phi-return.ll Normal file
View File

@ -0,0 +1,15 @@
; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | not grep br
define i1 @qux(i8* %m, i8* %n, i8* %o, i8* %p) nounwind {
entry:
%tmp7 = icmp eq i8* %m, %n
br i1 %tmp7, label %bb, label %UnifiedReturnBlock
bb:
%tmp15 = icmp eq i8* %o, %p
br label %UnifiedReturnBlock
UnifiedReturnBlock:
%result = phi i1 [ 0, %entry ], [ %tmp15, %bb ]
ret i1 %result
}