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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

llvm-svn: 101870
This commit is contained in:
Chris Lattner 2010-04-20 05:09:16 +00:00
parent 7a2ce4afd8
commit e5a995a834
2 changed files with 33 additions and 5 deletions
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19
lib/Transforms/Scalar/LoopUnswitch.cpp
View File

@ -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:

19
test/Transforms/LoopUnswitch/crash.ll
View File

@ -45,3 +45,22 @@ for.body: ; preds = %for.body, %bb.nph
for.end: ; preds = %for.body, %entry
ret void
}
; PR6879
define i32* @test3(i32** %p_45, i16 zeroext %p_46, i64 %p_47, i64 %p_48, i16 signext %p_49) nounwind {
entry:
br label %for.cond
for.cond: ; preds = %for.cond4, %entry
br i1 false, label %for.cond4, label %for.end88
for.cond4: ; preds = %for.cond
%conv46 = trunc i32 0 to i8 ; <i8> [#uses=2]
%cmp60 = icmp sgt i8 %conv46, 124 ; <i1> [#uses=1]
%or.cond = and i1 undef, %cmp60 ; <i1> [#uses=1]
%cond = select i1 %or.cond, i8 %conv46, i8 undef ; <i8> [#uses=0]
br label %for.cond
for.end88: ; preds = %for.cond
ret i32* undef
}