Hi, this is the first patch for PR78809 (totally 3 patches)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78809 inline strcmp with small constant strings The design doc is at: https://www.mail-archive.com/gcc@gcc.gnu.org/msg83822.html this patch is for the first part of change: A. for strncmp (s1, s2, n) if one of "s1" or "s2" is a constant string, "n" is a constant, and larger than the length of the constant string: change strncmp (s1, s2, n) to strcmp (s1, s2); adding test case strcmpopt_1.c into gcc.dg bootstraped and tested on both X86 and aarch64. no regression. Okay for commit? thanks. Qing ====================== gcc/ChangeLog 2017-11-15 Qing Zhao <qing.z...@oracle.com> * gimple-fold.c (gimple_fold_builtin_string_compare): Add handling of replacing call to strncmp with corresponding call to strcmp when meeting conditions. gcc/testsuite/ChangeLog 2017-11-15 Qing Zhao <qing.z...@oracle.com> PR middle-end/78809 * gcc.dg/strcmpopt_1.c: New test. --- gcc/gimple-fold.c | 15 +++++++++++++++ gcc/testsuite/gcc.dg/strcmpopt_1.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 43 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/strcmpopt_1.c diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c index adb6f3b..1ed6383 100644 --- a/gcc/gimple-fold.c +++ b/gcc/gimple-fold.c @@ -2258,6 +2258,21 @@ gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi) return true; } + /* If length is larger than the length of one constant string, + replace strncmp with corresponding strcmp */ + if (fcode == BUILT_IN_STRNCMP + && length > 0 + && ((p2 && (size_t) length > strlen (p2)) + || (p1 && (size_t) length > strlen (p1)))) + { + tree fn = builtin_decl_implicit (BUILT_IN_STRCMP); + if (!fn) + return false; + gimple *repl = gimple_build_call (fn, 2, str1, str2); + replace_call_with_call_and_fold (gsi, repl); + return true; + } + return false; } diff --git a/gcc/testsuite/gcc.dg/strcmpopt_1.c b/gcc/testsuite/gcc.dg/strcmpopt_1.c new file mode 100644 index 0000000..40596a2 --- /dev/null +++ b/gcc/testsuite/gcc.dg/strcmpopt_1.c @@ -0,0 +1,28 @@ +/* { dg-do run } */ +/* { dg-options "-fdump-tree-gimple" } */ + +#include <string.h> +#include <stdlib.h> + +int cmp1 (char *p) +{ + return strncmp (p, "fis", 4); +} +int cmp2 (char *q) +{ + return strncmp ("fis", q, 4); +} + +int main () +{ + + char *p = "fish"; + char *q = "fis\0"; + + if (cmp1 (p) == 0 || cmp2 (q) != 0) + abort (); + + return 0; +} + +/* { dg-final { scan-tree-dump-times "strcmp \\(" 2 "gimple" } } */ -- 1.9.1
