Hi! With -ffuse-ops-with-volatile-access which is now even on by default thie splitter can split a 16 or 32-bit volatile memory test into an 8-bit volatile memory test, which is undesirable and e.g. when it refers to some memory mapped hw registers it could misbehave.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk/16.2? 2026-05-05 Jakub Jelinek <[email protected]> PR target/125180 * config/i386/i386.md (HI/SI test -> QI test splitter): Punt if operands[2] is a volatile MEM. * gcc.target/i386/pr125180.c: New test. --- gcc/config/i386/i386.md.jj 2026-04-30 10:18:13.812688945 +0200 +++ gcc/config/i386/i386.md 2026-05-04 17:40:00.188612108 +0200 @@ -12772,6 +12772,7 @@ (define_split "reload_completed && GET_MODE (operands[2]) != QImode && (!REG_P (operands[2]) || ANY_QI_REG_P (operands[2])) + && !(MEM_P (operands[2]) && MEM_VOLATILE_P (operands[2])) && ((ix86_match_ccmode (insn, CCZmode) && !(INTVAL (operands[3]) & ~255)) || (ix86_match_ccmode (insn, CCNOmode) --- gcc/testsuite/gcc.target/i386/pr125180.c.jj 2026-05-04 17:47:37.651134771 +0200 +++ gcc/testsuite/gcc.target/i386/pr125180.c 2026-05-04 17:47:19.826426119 +0200 @@ -0,0 +1,14 @@ +/* PR target/125180 */ +/* { dg-do compile } */ +/* { dg-options "-O2 -masm=att" } */ +/* { dg-final { scan-assembler "\ttestl\t\\\$1, \\\(" } } */ +/* { dg-final { scan-assembler-not "\ttestb\t\\\$1, \\\(" } } */ + +void foo (void); + +void +bar (unsigned volatile *x) +{ + if (*x & 1) + foo (); +} Jakub
