On Wed, Aug 19, 2020 at 6:25 AM H.J. Lu <hjl.to...@gmail.com> wrote: > > On Wed, Jul 15, 2020 at 10:42:27AM -0700, H.J. Lu wrote: > > Expand strncmp to "repz cmpsb" only with -minline-all-stringops since > > "repz cmpsb" can be much slower than strncmp function implemented with > > vector instructions, see > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43052 > > > > gcc/ > > > > PR target/95458 > > * config/i386/i386-expand.c (ix86_expand_cmpstrn_or_cmpmem): > > Return false for -mno-inline-all-stringops. > > > > gcc/testsuite/ > > > > PR target/95458 > > * gcc.target/i386/pr95458-1.c: New test. > > * gcc.target/i386/pr95458-2.c: Likewise. > > Expand strncmp to "repz cmpsb" only with -minline-all-stringops since > "repz cmpsb" can be much slower than strncmp function implemented with > vector instructions, see > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43052 > > gcc/ > > PR target/95458 > * config/i386/i386.md (cmpstrnsi): Expand only with > TARGET_INLINE_ALL_STRINGOPS. > > gcc/testsuite/ > > PR target/95458 > * gcc.target/i386/pr95458-1.c: New test. > * gcc.target/i386/pr95458-2.c: Likewise. > --- > gcc/config/i386/i386.md | 8 +++++++- > gcc/testsuite/gcc.target/i386/pr95458-1.c | 11 +++++++++++ > gcc/testsuite/gcc.target/i386/pr95458-2.c | 7 +++++++ > 3 files changed, 25 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/gcc.target/i386/pr95458-1.c > create mode 100644 gcc/testsuite/gcc.target/i386/pr95458-2.c > > diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md > index fb677e17817..f3fbed81c4a 100644 > --- a/gcc/config/i386/i386.md > +++ b/gcc/config/i386/i386.md > @@ -18007,7 +18007,13 @@ (define_expand "cmpstrnsi" > { > rtx addr1, addr2, countreg, align, out; > > - if (optimize_insn_for_size_p () && !TARGET_INLINE_ALL_STRINGOPS) > + /* Expand strncmp only with -minline-all-stringops since > + "repz cmpsb" can be much slower than strncmp functions > + implemented with vector instructions, see > + > + https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43052 > + */ > + if (!TARGET_INLINE_ALL_STRINGOPS) > FAIL; > > /* Can't use this if the user has appropriated ecx, esi or edi. */ > diff --git a/gcc/testsuite/gcc.target/i386/pr95458-1.c > b/gcc/testsuite/gcc.target/i386/pr95458-1.c > new file mode 100644 > index 00000000000..231a4787dce > --- /dev/null > +++ b/gcc/testsuite/gcc.target/i386/pr95458-1.c > @@ -0,0 +1,11 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -minline-all-stringops" } */ > + > +int > +func (char *d, unsigned int l) > +{ > + return __builtin_strncmp (d, "foo", l) ? 1 : 2; > +} > + > +/* { dg-final { scan-assembler-not "call\[\\t \]*_?strncmp" } } */ > +/* { dg-final { scan-assembler "cmpsb" } } */ > diff --git a/gcc/testsuite/gcc.target/i386/pr95458-2.c > b/gcc/testsuite/gcc.target/i386/pr95458-2.c > new file mode 100644 > index 00000000000..1a620444770 > --- /dev/null > +++ b/gcc/testsuite/gcc.target/i386/pr95458-2.c > @@ -0,0 +1,7 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -mno-inline-all-stringops" } */ > + > +#include "pr95458-1.c" > + > +/* { dg-final { scan-assembler "call\[\\t \]*_?strncmp" } } */ > +/* { dg-final { scan-assembler-not "cmpsb" } } */ > -- > 2.26.2 >
PING. -- H.J.
