diff options
Diffstat (limited to 'gcc/gimple-fold.c')
| -rw-r--r-- | gcc/gimple-fold.c | 92 |
1 files changed, 65 insertions, 27 deletions
diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c index e176be8..cfae9db 100644 --- a/gcc/gimple-fold.c +++ b/gcc/gimple-fold.c @@ -2323,8 +2323,7 @@ gimple_load_first_char (location_t loc, tree str, gimple_seq *stmts) return var; } -/* Fold a call to the str{n}{case}cmp builtin pointed by GSI iterator. - FCODE is the name of the builtin. */ +/* Fold a call to the str{n}{case}cmp builtin pointed by GSI iterator. */ static bool gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi) @@ -2337,18 +2336,19 @@ gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi) tree str1 = gimple_call_arg (stmt, 0); tree str2 = gimple_call_arg (stmt, 1); tree lhs = gimple_call_lhs (stmt); - HOST_WIDE_INT length = -1; + tree len = NULL_TREE; + unsigned HOST_WIDE_INT bound = HOST_WIDE_INT_M1U; /* Handle strncmp and strncasecmp functions. */ if (gimple_call_num_args (stmt) == 3) { - tree len = gimple_call_arg (stmt, 2); + len = gimple_call_arg (stmt, 2); if (tree_fits_uhwi_p (len)) - length = tree_to_uhwi (len); + bound = tree_to_uhwi (len); } /* If the LEN parameter is zero, return zero. */ - if (length == 0) + if (bound == 0) { replace_call_with_value (gsi, integer_zero_node); return true; @@ -2361,8 +2361,32 @@ gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi) return true; } - const char *p1 = c_getstr (str1); - const char *p2 = c_getstr (str2); + /* Initially set to the number of characters, including the terminating + nul if each array has one. LENx == strnlen (Sx, LENx) implies that + the array Sx is not terminated by a nul. + For nul-terminated strings then adjusted to their length so that + LENx == NULPOSx holds. */ + unsigned HOST_WIDE_INT len1 = HOST_WIDE_INT_MAX, len2 = len1; + const char *p1 = c_getstr (str1, &len1); + const char *p2 = c_getstr (str2, &len2); + + /* The position of the terminating nul character if one exists, otherwise + a value greater than LENx. */ + unsigned HOST_WIDE_INT nulpos1 = HOST_WIDE_INT_MAX, nulpos2 = nulpos1; + + if (p1) + { + size_t n = strnlen (p1, len1); + if (n < len1) + len1 = nulpos1 = n; + } + + if (p2) + { + size_t n = strnlen (p2, len2); + if (n < len2) + len2 = nulpos2 = n; + } /* For known strings, return an immediate value. */ if (p1 && p2) @@ -2374,17 +2398,30 @@ gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi) { case BUILT_IN_STRCMP: case BUILT_IN_STRCMP_EQ: - { - r = strcmp (p1, p2); - known_result = true; + if (len1 != nulpos1 || len2 != nulpos2) break; - } + + r = strcmp (p1, p2); + known_result = true; + break; + case BUILT_IN_STRNCMP: case BUILT_IN_STRNCMP_EQ: { - if (length == -1) + /* Reduce the bound to be no more than the length + of the shorter of the two strings, or the sizes + of the unterminated arrays. */ + unsigned HOST_WIDE_INT n = bound; + + if (len1 == nulpos1 && len1 < n) + n = len1 + 1; + if (len2 == nulpos2 && len2 < n) + n = len2 + 1; + + if (MIN (nulpos1, nulpos2) + 1 < n) break; - r = strncmp (p1, p2, length); + + r = strncmp (p1, p2, n); known_result = true; break; } @@ -2394,9 +2431,9 @@ gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi) break; case BUILT_IN_STRNCASECMP: { - if (length == -1) + if (bound == HOST_WIDE_INT_M1U) break; - r = strncmp (p1, p2, length); + r = strncmp (p1, p2, bound); if (r == 0) known_result = true; break; @@ -2412,7 +2449,7 @@ gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi) } } - bool nonzero_length = length >= 1 + bool nonzero_bound = (bound >= 1 && bound < HOST_WIDE_INT_M1U) || fcode == BUILT_IN_STRCMP || fcode == BUILT_IN_STRCMP_EQ || fcode == BUILT_IN_STRCASECMP; @@ -2420,7 +2457,7 @@ gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi) location_t loc = gimple_location (stmt); /* If the second arg is "", return *(const unsigned char*)arg1. */ - if (p2 && *p2 == '\0' && nonzero_length) + if (p2 && *p2 == '\0' && nonzero_bound) { gimple_seq stmts = NULL; tree var = gimple_load_first_char (loc, str1, &stmts); @@ -2435,7 +2472,7 @@ gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi) } /* If the first arg is "", return -*(const unsigned char*)arg2. */ - if (p1 && *p1 == '\0' && nonzero_length) + if (p1 && *p1 == '\0' && nonzero_bound) { gimple_seq stmts = NULL; tree var = gimple_load_first_char (loc, str2, &stmts); @@ -2454,9 +2491,9 @@ gimple_fold_builtin_string_compare (gimple_stmt_iterator *gsi) return true; } - /* If len parameter is one, return an expression corresponding to + /* If BOUND is one, return an expression corresponding to (*(const unsigned char*)arg2 - *(const unsigned char*)arg1). */ - if (fcode == BUILT_IN_STRNCMP && length == 1) + if (fcode == BUILT_IN_STRNCMP && bound == 1) { gimple_seq stmts = NULL; tree temp1 = gimple_load_first_char (loc, str1, &stmts); @@ -2480,12 +2517,13 @@ 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)))) + /* If BOUND is greater than the length of one constant string, + and the other argument is also a nul-terminated string, replace + strncmp with strcmp. */ + if (fcode == BUILT_IN_STRNCMP + && bound > 0 && bound < HOST_WIDE_INT_M1U + && ((p2 && len2 < bound && len2 == nulpos2) + || (p1 && len1 < bound && len1 == nulpos1))) { tree fn = builtin_decl_implicit (BUILT_IN_STRCMP); if (!fn) |