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