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Fix my previous patch to handle a degenerate case that the llvm-gcc 

bootstrap buildbot tripped over.

llvm-svn: 121674
This commit is contained in:
Chris Lattner 2010-12-13 03:43:57 +00:00
parent 11dafaa3ec
commit 62cc76e9cc
2 changed files with 39 additions and 0 deletions
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16
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -1820,6 +1820,22 @@ static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI) {
return SimplifyCFG(BB) | true;
}
// Ok, the block is reachable from the default dest. If the constant we're
// comparing exists in one of the other edges, then we can constant fold ICI
// and zap it.
if (SI->findCaseValue(Cst) != 0) {
Value *V;
if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
V = ConstantInt::getFalse(BB->getContext());
else
V = ConstantInt::getTrue(BB->getContext());
ICI->replaceAllUsesWith(V);
ICI->eraseFromParent();
// BB is now empty, so it is likely to simplify away.
return SimplifyCFG(BB) | true;
}
// The use of the icmp has to be in the 'end' block, by the only PHI node in
// the block.
BasicBlock *SuccBlock = BB->getTerminator()->getSuccessor(0);

23
llvm/test/Transforms/SimplifyCFG/switch_create.ll
View File

@ -88,3 +88,26 @@ lor.end: ; preds = %lor.rhs, %lor.lhs.f
; CHECK: ]
}
define i32 @test5(i8 zeroext %c) nounwind ssp noredzone {
entry:
switch i8 %c, label %lor.rhs [
i8 62, label %lor.end
i8 34, label %lor.end
i8 92, label %lor.end
]
lor.rhs: ; preds = %entry
%V = icmp eq i8 %c, 92
br label %lor.end
lor.end: ; preds = %entry, %entry, %entry, %lor.rhs
%0 = phi i1 [ true, %entry ], [ %V, %lor.rhs ], [ true, %entry ], [ true, %entry ]
%lor.ext = zext i1 %0 to i32
ret i32 %lor.ext
; CHECK: @test5
; CHECK: switch i8 %c, label %lor.rhs [
; CHECK: i8 62, label %lor.end
; CHECK: i8 34, label %lor.end
; CHECK: i8 92, label %lor.end
; CHECK: ]
}