https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111597
Bug ID: 111597
Summary: pattern "(T)(A)+cst -->(T)(A+cst)" cause suboptimal
for ppc64
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: guojiufu at gcc dot gnu.org
Target Milestone: ---
In match.pd there is a pattern:
/* ((T)(A)) + CST -> (T)(A + CST) */
#if GIMPLE
(simplify
(plus (convert:s SSA_NAME@0) INTEGER_CST@1)
(if (TREE_CODE (TREE_TYPE (@0)) == INTEGER_TYPE
&& TREE_CODE (type) == INTEGER_TYPE
&& TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0))
&& int_fits_type_p (@1, TREE_TYPE (@0)))
/* Perform binary operation inside the cast if the constant fits
and (A + CST)'s range does not overflow. *
But this pattern seems not in favor of all targets.
For example, the below code hits this pattern,
long foo1 (int x)
{
if (x>1000)
return 0;
int x1 = x +1;
return (long) x1 + 40;
}
Compile with "-O2 -S", on ppc64le, the generated asm is:
cmpwi 0,3,1000
bgt 0,.L3
addi 3,3,41
extsw 3,3 ;; this is suboptimal
blr
.p2align 4,,15
.L3:
li 3,0
blr
--------------
But for the below code, the generated asm seems better: without
long foo1 (int x)
{
if (x>1000)
return 0;
return (long) x + 40;
}
cmpwi 0,3,1000
bgt 0,.L3
addi 3,3,40
blr
.p2align 4,,15
.L3:
li 3,0
blr
