[LLVMdev] troubles with ISD::FPOWI

[Richard Gorton]

I'm missing something - I tried that, and also adding some code to PromoteIntegerOperand to do that, but get other errors.
I submitted bug 21042 (with the .ll file as an example)


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.
> 
>