[llvm-commits] [llvm] r168931 - in /llvm/trunk: include/llvm/Target/TargetTransformImpl.h include/llvm/TargetTransformInfo.h lib/Target/X86/X86ISelLowering.cpp lib/Target/X86/X86ISelLowering.h lib/Target/X86/X86TargetMachine.h lib/Transforms/Scalar/LoopIdiomRecognize.cpp test/Transforms/LoopIdiom/popcnt.ll

[Shuxin Yang]

Hi, Chandler:

   Thank you for pointing out the problem. Yes, the "&&" should be 
replaced with "||".
I will commit the fix after some tests.  I don't feel like to include a 
testing case for
such inadvertent bug.

    Following is the contrived *.ll to reproduce the problem.


   /the/path/to/opt  -loop-idiom -mtriple=x86_64-apple-darwin 
-mcpu=corei7 a.ll -S -o -

cat a.ll

target triple = "x86_64-apple-macosx10.8.0"

define i32 @PopCnt(i64 %a) nounwind uwtable readnone ssp {
entry:
   %tobool3 = icmp eq i64 %a, 0
   br i1 %tobool3, label %while.end, label %while.body

while.body:                                       ; preds = %entry, 
%while.body
   %c.05 = phi i32 [ %inc, %while.body ], [ 0, %entry ]
   %a.addr.04 = phi i64 [ %and, %while.body ], [ %a, %entry ]
   %t = add i32 %c.05, %c.05
   %inc = add nsw i32 %t, 1
   %sub = add i64 %a.addr.04, -1
   %and = and i64 %sub, %a.addr.04
   %tobool = icmp eq i64 %and, 0
   br i1 %tobool, label %while.end, label %while.body

while.end:                                        ; preds = %while.body, 
%entry
   %c.0.lcssa = phi i32 [ 0, %entry ], [ %inc, %while.body ]
   ret i32 %c.0.lcssa
}





> This is incorrect, and will crash LLVM on certain inputs: if InitConst 
> is null here, we pass the test and pass it to CreateAdd below that 
> eventually segfaults. Please fix, and please add a test case for this 
> case. I spotted it by inspection (after some code in the wild 
> crashed). I can try to help you with a testcase if you need, but it 
> should be quite straight forward to synthesize one.
> -------
>
> Here is the snippet regarding the other one I spotted by inspection:
> ----
>
>     +      PHINode *Phi = dyn_cast<PHINode>(Inst->getOperand(0));
>     +      if (!Phi && Phi->getParent() != LoopEntry)
>
>
>

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