[LLVMdev] troubles with ISD::FPOWI

[Duncan Sands]

Hi Richard,

On 23/09/14 16:19, Richard Gorton wrote:
>
> I'm missing something - I tried that, and also adding some code to PromoteIntegerOperand to do that, but get other errors.

using SExtPromotedInteger as I suggested is more efficient than using 
SIGN_EXTEND[_INREG], but indeed the result will be the same.

> I submitted bug 21042 (with the .ll file as an example)

Please also attach the patch(es) you tried and the assertions you hit.

Ciao, Duncan.

>
>
> On Sep 21, 2014, at 5:15 AM, Duncan Sands <duncan.sands at deepbluecap.com> wrote:
>
>> Hi Richard,
>>
>> On 18/09/14 19:25, Richard Gorton wrote:
>>>
>>> Hi,
>>>
>>> I'm stumped by how to handle fpowi.  Here is the context: my architecture has i64, f32, and f64 registers.  No i32.  For calls & returns, we promote i32 to i64.  There is no support in the architecture to perform fpowi - it has to go through the runtime.
>>>
>>> I'm using gfortran + dragonegg + llvm3.4 to generate .ll files via plugin.
>>> The fortran expression
>>> 	REAL = REAL ** INTEGER*4
>>> Resulting in:
>>>    %4 = call float @llvm.powi.f32(float %1, i32 %3)
>>>
>>> So far, not unreasonable.
>>> But when I run this through the compiler, it asserts:
>>>
>>> -bash-4.1$ $DEVCLANG -target coge -O -S slamchf77.ll -mllvm -debug
>>> ...
>>> Promote integer result: 0x56061c0: i32 = sub 0x56049a0, 0x56046a0 [ORD=161] [ID=0]
>>>
>>> Promote integer operand: 0x56059c0: f32 = fpowi 0x5602580, 0x56061c0 [ORD=162] [ID=0]
>>>
>>> PromoteIntegerOperand Op #1: 0x56059c0: f32 = fpowi 0x5602580, 0x56061c0 [ORD=162] [ID=0]
>>>
>>> Do not know how to promote this operator's operand!
>>
>> you probably want to do the following: add a method for FPOWI in PromoteIntegerResult.  In the method, get the i64 version of the second operand using:
>>     SDValue Op = SExtPromotedInteger(N->getOperand(1));
>> Create and return a new FPOWI node that is the same as the original, only it uses Op as the second operand.
>>
>> Ciao, Duncan.
>>
>>
>