https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93123
Bug ID: 93123
Summary: Lacking basic optimization around __int128 bitwise
operations against constants
Product: gcc
Version: 8.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jens.seifert at de dot ibm.com
Target Milestone: ---
unsigned __int128 and128WithConst(unsigned __int128 a)
{
unsigned __int128 c128 = (((unsigned __int128)(~0ULL)) << 64) | ((unsigned
__int128)(~0xFULL));
return a & c128;
}
gcc -O2 -maix64 -save-temps int128.C
Output:
._Z12andWithConsto:
LFB..0:
li 10,-1
li 11,-16
and 3,3,10
and 4,4,11
blr
Expected result: Single instruction: rldicr on low part (register 4).
Bitwise and with 0xFF..FF is a no-op.
Bitwise and with 0xFF..F0 can be done using rldicr.
