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From: "jens.seifert at de dot ibm.com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/102117] s390: Inefficient code for 64x64=128 signed multiply for <= z13
Date: Sun, 29 Aug 2021 12:49:14 +0000 [thread overview]
Message-ID: <bug-102117-4-3kJAVLUeo1@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-102117-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102117
--- Comment #1 from Jens Seifert <jens.seifert at de dot ibm.com> ---
Sorry small bug in optimal sequence.
__int128 imul128_opt(long long a, long long b)
{
unsigned __int128 x = (unsigned __int128)(unsigned long long)a;
unsigned __int128 y = (unsigned __int128)(unsigned long long)b;
unsigned long long t1 = (a >> 63) & b;
unsigned long long t2 = (b >> 63) & a;
unsigned __int128 u128 = x * y;
unsigned long long hi = (u128 >> 64) - (t1 + t2);
unsigned long long lo = (unsigned long long)u128;
unsigned __int128 res = hi;
res <<= 64;
res |= lo;
return (__int128)res;
}
_Z11imul128_optxx:
.LFB1:
.cfi_startproc
ldgr %f2,%r12
.cfi_register 12, 17
ldgr %f0,%r13
.cfi_register 13, 16
lgr %r13,%r3
mlgr %r12,%r4
srag %r1,%r3,63
ngr %r1,%r4
srag %r4,%r4,63
ngr %r4,%r3
agr %r4,%r1
sgrk %r4,%r12,%r4
stg %r13,8(%r2)
lgdr %r12,%f2
.cfi_restore 12
lgdr %r13,%f0
.cfi_restore 13
stg %r4,0(%r2)
br %r14
.cfi_endproc
next prev parent reply other threads:[~2021-08-29 12:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-29 12:30 [Bug target/102117] New: " jens.seifert at de dot ibm.com
2021-08-29 12:49 ` jens.seifert at de dot ibm.com [this message]
2021-11-20 13:16 ` [Bug target/102117] " roger at nextmovesoftware dot com
2021-11-21 11:41 ` cvs-commit at gcc dot gnu.org
2021-11-25 19:17 ` roger at nextmovesoftware dot com
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