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

[Eli Friedman]

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.

Also, missing testcase.

-Eli