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RewriteLoopBodyWithConditionConstant can end up rewriting the

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condition we're unswitching on.  In this case, don't try to
simplify the second copy of the loop which may be dead or not,
but is probably a constant now.  This fixes PR6879


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101870 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2010-04-20 05:09:16 +00:00
parent f1cfb95337
commit a78130c320
2 changed files with 33 additions and 5 deletions
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lib/Transforms/Scalar/LoopUnswitch.cpp
+14 -5
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@@ -677,15 +677,22 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
LoopProcessWorklist.push_back(NewLoop);
redoLoop = true;
// Keep a WeakVH holding onto LIC. If the first call to RewriteLoopBody
// deletes the instruction (for example by simplifying a PHI that feeds into
// the condition that we're unswitching on), we don't rewrite the second
// iteration.
WeakVH LICHandle(LIC);
// Now we rewrite the original code to know that the condition is true and the
// new code to know that the condition is false.
RewriteLoopBodyWithConditionConstant(L, LIC, Val, false);
// It's possible that simplifying one loop could cause the other to be
// deleted. If so, don't simplify it.
if (!LoopProcessWorklist.empty() && LoopProcessWorklist.back() == NewLoop)
RewriteLoopBodyWithConditionConstant(NewLoop, LIC, Val, true);
// It's possible that simplifying one loop could cause the other to be
// changed to another value or a constant. If its a constant, don't simplify
// it.
if (!LoopProcessWorklist.empty() && LoopProcessWorklist.back() == NewLoop &&
LICHandle && !isa<Constant>(LICHandle))
RewriteLoopBodyWithConditionConstant(NewLoop, LICHandle, Val, true);
}
/// RemoveFromWorklist - Remove all instances of I from the worklist vector
@@ -981,6 +988,8 @@ void LoopUnswitch::SimplifyCode(std::vector<Instruction*> &Worklist, Loop *L) {
continue;
}
// FIXME: Change this to use instruction simplify interfaces!
// Special case hacks that appear commonly in unswitched code.
switch (I->getOpcode()) {
case Instruction::Select: