[LLVMdev] troubles with ISD::FPOWI

[Duncan Sands]

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.


>
> ------
> This is coming out of DAGTypeLegalizer::ExpandIntegerResult().
> I've tried adding some code to expand the integer operand (operand 1) via SIGN_EXTEND[_INREG] but keep getting other consistency errors.
>
> Another approach I tried was to set the calling convention:
> 	setLibcallCallingConv(RTLIB::POWI_F32, CallingConv::C);
> Which would seem to force the call to convert the i32 --> i64 just like any other call, but that did not work either
>
> Any suggestions (is this a real bug? - when I give other 64-bit targets, they also bomb out (sparcv9, aarch64)
>
> Regards,
>
> 	Richard Gorton
> 	Cognitive Electronics
> 	www.cog-e.com
>
>
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