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Re: A case where PHI-OPT pessimizes the code
On Mon, Apr 23, 2012 at 2:27 PM, Richard Guenther
<richard.guenther@gmail.com> wrote:
> int foo (_Bool b)
> {
> ?if (b)
> ? ?return 1;
> ?else
> ? ?return 0;
> }
Indeed PHI-OPT performs the transformation on this code, too. But the
resulting code on powerpc64 is fine:
[stevenb@gcc1-power7 gcc]$ cat t.c.149t.optimized
;; Function foo (foo, funcdef_no=0, decl_uid=1996, cgraph_uid=0)
foo (_Bool b)
{
int D.2006;
<bb 2>:
D.2006_4 = (int) b_2(D);
return D.2006_4;
}
[stevenb@gcc1-power7 gcc]$ cat t.s
.file "t.c"
.section ".toc","aw"
.section ".text"
.align 2
.p2align 4,,15
.globl foo
.section ".opd","aw"
.align 3
foo:
.quad .L.foo,.TOC.@tocbase,0
.previous
.type foo, @function
.L.foo:
blr
.long 0
.byte 0,0,0,0,0,0,0,0
.size foo,.-.L.foo
.ident "GCC: (GNU) 4.8.0 20120418 (experimental) [trunk
revision 186580]"
[stevenb@gcc1-power7 gcc]$
However, this C test case shows the problem:
[stevenb@gcc1-power7 gcc]$ head -n 24 t.c
#define ONEUL (1UL)
int
foo (long unsigned int a)
{
_Bool b;
long unsigned int cst, csui;
if (a > 27) goto return_zero;
/*cst = 217579583UL;*/
cst = (ONEUL << 0) | (ONEUL << 1) | (ONEUL << 2) | (ONEUL << 3)
| (ONEUL << 4) |
(ONEUL << 5) | (ONEUL << 19) | (ONEUL << 20) | (ONEUL << 21)
| (ONEUL << 22) |
(ONEUL << 23) | (ONEUL << 26) | (ONEUL << 27);
csui = (ONEUL << a);
b = ((csui & cst) != 0);
if (b)
return 1;
else
return 0;
return_zero:
return 0;
}
[stevenb@gcc1-power7 gcc]$ ./cc1 -quiet -O2 -fdump-tree-all t.c
[stevenb@gcc1-power7 gcc]$ cat t.s
.file "t.c"
.section ".toc","aw"
.section ".text"
.align 2
.p2align 4,,15
.globl foo
.section ".opd","aw"
.align 3
foo:
.quad .L.foo,.TOC.@tocbase,0
.previous
.type foo, @function
.L.foo:
cmpldi 7,3,27
bgt 7,.L3
li 10,1
lis 9,0xcf8
sld 3,10,3
ori 9,9,63
and. 10,3,9
mfcr 9
rlwinm 9,9,3,1
xori 3,9,1
blr
.p2align 4,,15
.L3:
.L2:
li 3,0
blr
.long 0
.byte 0,0,0,0,0,0,0,0
.size foo,.-.L.foo
.ident "GCC: (GNU) 4.8.0 20120418 (experimental) [trunk
revision 186580]"
I will file a PR for this later today, maybe after trying on a few
other targets to see if this is a middle-end problem or a target
issue.
Ciao!
Steven