[llvm-commits] [llvm] r152847 - /llvm/trunk/lib/Target/ARM/ARMFastISel.cpp

[Chad Rosier]

Eli's comments have been addressed in r152869.  Thanks, Eli!

 Chad

On Mar 15, 2012, at 3:37 PM, Chad Rosier <mcrosier at apple.com> wrote:

> 
> On Mar 15, 2012, at 3:06 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
> 
>> On Thu, Mar 15, 2012 at 2:40 PM, Chad Rosier <mcrosier at apple.com> wrote:
>>> Author: mcrosier
>>> Date: Thu Mar 15 16:40:23 2012
>>> New Revision: 152847
>>> 
>>> URL: http://llvm.org/viewvc/llvm-project?rev=152847&view=rev
>>> Log:
>>> [fast-isel] Don't try to encode LONG_MIN using cmn instructions.
>>> rdar://11038907
>>> 
>>> Modified:
>>>   llvm/trunk/lib/Target/ARM/ARMFastISel.cpp
>>> 
>>> Modified: llvm/trunk/lib/Target/ARM/ARMFastISel.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMFastISel.cpp?rev=152847&r1=152846&r2=152847&view=diff
>>> ==============================================================================
>>> --- llvm/trunk/lib/Target/ARM/ARMFastISel.cpp (original)
>>> +++ llvm/trunk/lib/Target/ARM/ARMFastISel.cpp Thu Mar 15 16:40:23 2012
>>> @@ -1384,12 +1384,16 @@
>>>        SrcVT == MVT::i1) {
>>>      const APInt &CIVal = ConstInt->getValue();
>>>      Imm = (isZExt) ? (int)CIVal.getZExtValue() : (int)CIVal.getSExtValue();
>>> -      if (Imm < 0) {
>>> -        isNegativeImm = true;
>>> -        Imm = -Imm;
>>> +      // We can't encode LONG_MIN (i.e., 0x80000000) as an immediate because
>>> +      // there is no way to represent 2147483648 as a signed 32-bit int.
>>> +      if (Imm != (int)0x80000000) {
>>> +        if (Imm < 0) {
>>> +          isNegativeImm = true;
>>> +          Imm = -Imm;
>>> +        }
>>> +        UseImm = isThumb2 ? (ARM_AM::getT2SOImmVal(Imm) != -1) :
>>> +          (ARM_AM::getSOImmVal(Imm) != -1);
>>>      }
>>> -      UseImm = isThumb2 ? (ARM_AM::getT2SOImmVal(Imm) != -1) :
>>> -        (ARM_AM::getSOImmVal(Imm) != -1);
>> 
>> Why not just skip the negation rather than forcing it not to use an
>> immediate?  ARM_AM::getT2SOImmVal(INT_MIN) will succeed, AFAIK.
> 
> Ah, yes.  That would be a better fix.  I'll double check if it works.
> 
>> Also, missing test case.
> 
> Coming up!
> 
> Thanks, Eli.	
> 
>> -Eli
> 
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