https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103605
Bug ID: 103605
Summary: [PowerPC] fmin/fmax should be inlined always with
xsmindp/xsmaxdp
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: pc at gcc dot gnu.org
Target Milestone: ---
--
$ gcc --version
gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-2)
[...]
$ gcc -c -O2 fmin.c && objdump -dr fmin.o
0: 00 00 4c 3c addis r2,r12,0
0: R_PPC64_REL16_HA .TOC.
4: 00 00 42 38 addi r2,r2,0
4: R_PPC64_REL16_LO .TOC.+0x4
8: a6 02 08 7c mflr r0
c: 10 00 01 f8 std r0,16(r1)
10: e1 ff 21 f8 stdu r1,-32(r1)
14: 01 00 00 48 bl 14 <fm+0x14>
14: R_PPC64_REL24 fmin
18: 00 00 00 60 nop
1c: 20 00 21 38 addi r1,r1,32
20: 10 00 01 e8 ld r0,16(r1)
24: a6 03 08 7c mtlr r0
28: 20 00 80 4e blr
$ gcc -c -O2 fmin.c -ffast-math && objdump -dr fmin.o
0: 40 14 21 f0 xsmincdp vs1,vs1,vs2
4: 20 00 80 4e blr
--
And it appears that a better instruction choice in the above case is xsmindp,
and it can be used with and without "-ffast-math", as it matches the semantics
required of fmin. Similarly, xsmaxdp with fmax.
