https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109019
Bug ID: 109019
Summary: Failure to optimize b + c -1
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: tkoenig at gcc dot gnu.org
Target Milestone: ---
Looks like a general RTL issue, I see this on POWER, RV64 and ARM64 (the
latter two on godbolt).
[tkoenig@gcc135 ~]$ cat c.c
long foo (long b, long c)
{
return b + c - 1;
}
[tkoenig@gcc135 ~]$ gcc -O3 -S c.c
[tkoenig@gcc135 ~]$ cat c.s
.file "c.c"
.machine power8
.abiversion 2
.section ".text"
.align 2
.p2align 4,,15
.globl foo
.type foo, @function
foo:
.LFB0:
.cfi_startproc
add 3,3,4
addi 3,3,-1
blr
.long 0
.byte 0,0,0,0,0,0,0,0
.cfi_endproc
.LFE0:
.size foo,.-foo
.ident "GCC: (GNU) 13.0.1 20230215 (experimental)"
.section .note.GNU-stack,"",@progbits
This should be
addi 3,4,-1
ret
