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* [Bug target/108048] New: PPCLE: gcc does not recognize that lbzx does zero extend
@ 2022-12-10 12:06 jens.seifert at de dot ibm.com
2022-12-10 12:09 ` [Bug target/108048] " jens.seifert at de dot ibm.com
0 siblings, 1 reply; 2+ messages in thread
From: jens.seifert at de dot ibm.com @ 2022-12-10 12:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108048
Bug ID: 108048
Summary: PPCLE: gcc does not recognize that lbzx does zero
extend
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: jens.seifert at de dot ibm.com
Target Milestone: ---
extern unsigned char magic1[256];
unsigned int hash(const unsigned char inp[4])
{
const unsigned long long INIT = 0x1ULL;
unsigned long long h1 = INIT;
h1 = magic1[((unsigned long long)inp[0]) ^ h1];
h1 = magic1[((unsigned long long)inp[1]) ^ h1];
h1 = magic1[((unsigned long long)inp[2]) ^ h1];
h1 = magic1[((unsigned long long)inp[3]) ^ h1];
return h1;
}
Generates:
hash(unsigned char const*):
.LCF0:
addi 2,2,.TOC.-.LCF0@l
lbz 9,0(3)
addis 10,2,.LC0@toc@ha
ld 10,.LC0@toc@l(10)
lbz 6,1(3)
lbz 7,2(3)
lbz 8,3(3)
xori 9,9,0x1
lbzx 9,10,9
xor 9,9,6
rlwinm 9,9,0,0xff <= unnecessary
lbzx 9,10,9
xor 9,9,7
rlwinm 9,9,0,0xff <= unnecessary
lbzx 9,10,9
xor 9,9,8
rlwinm 9,9,0,0xff <= unnecessary
lbzx 3,10,9
blr
All XOR operations are done in unsigned long long (64-bit). gcc adds
unnecessary rlwinm. lbz and lbzx does zero extension (no cleanup of upper bits
required).
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug target/108048] PPCLE: gcc does not recognize that lbzx does zero extend
2022-12-10 12:06 [Bug target/108048] New: PPCLE: gcc does not recognize that lbzx does zero extend jens.seifert at de dot ibm.com
@ 2022-12-10 12:09 ` jens.seifert at de dot ibm.com
0 siblings, 0 replies; 2+ messages in thread
From: jens.seifert at de dot ibm.com @ 2022-12-10 12:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108048
Jens Seifert <jens.seifert at de dot ibm.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #1 from Jens Seifert <jens.seifert at de dot ibm.com> ---
duplicate of https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107949
*** This bug has been marked as a duplicate of bug 107949 ***
^ permalink raw reply [flat|nested] 2+ messages in thread
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2022-12-10 12:06 [Bug target/108048] New: PPCLE: gcc does not recognize that lbzx does zero extend jens.seifert at de dot ibm.com
2022-12-10 12:09 ` [Bug target/108048] " jens.seifert at de dot ibm.com
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