https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85819
Bug ID: 85819
Summary: conversion from __v[48]su to __v[48]sf should use FMA
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: kretz at kde dot org
Target Milestone: ---
Testcase (cf. https://godbolt.org/g/UoU3zj):
using T = float;
using To [[gnu::vector_size(32)]] = T;
using From [[gnu::vector_size(32)]] = unsigned;
#define A2(I) (T)a[I], (T)a[1+I]
#define A4(I) A2(I), A2(2+I)
#define A8(I) A4(I), A4(4+I)
To f(From a) {
return To{A8(0)};
}
This compiles to:
vpand .LC0(%rip), %ymm0, %ymm1
vpsrld $16, %ymm0, %ymm0
vcvtdq2ps %ymm0, %ymm0
vcvtdq2ps %ymm1, %ymm1
vmulps .LC1(%rip), %ymm0, %ymm0
vaddps %ymm0, %ymm1, %ymm0
ret
The last vmulps and vaddps can be contracted to vfmadd132ps .LC1(%rip), %ymm1,
%ymm0.
The same is true for vector_size(16).
