apr_cstr: Improve apr_cstr_casecmp() and apr_cstr_casecmpn() performances.

The new versions [1] compile to a shorter/faster assembly than the previous
ones [2], no functionnal change.

[1] apr_cstr_casecmp() after this commit:
Dump of assembler code for function apr_cstr_casecmp:
   0x0000000000049fc0 <+0>:     movzbl (%rdi),%eax
   0x0000000000049fc3 <+3>:     movzbl (%rsi),%edx
   0x0000000000049fc6 <+6>:     lea    0x3d573(%rip),%r8        # 0x87540 <ucharmap>
   0x0000000000049fcd <+13>:    movzbl (%r8,%rax,1),%eax
   0x0000000000049fd2 <+18>:    movzbl (%r8,%rdx,1),%ecx
   0x0000000000049fd7 <+23>:    cmp    %ecx,%eax
   0x0000000000049fd9 <+25>:    jne    0x49ffe <apr_cstr_casecmp+62>
   0x0000000000049fdb <+27>:    xor    %edx,%edx
   0x0000000000049fdd <+29>:    jmp    0x49ffa <apr_cstr_casecmp+58>
   0x0000000000049fdf <+31>:    nop
   0x0000000000049fe0 <+32>:    add    $0x1,%rdx
   0x0000000000049fe4 <+36>:    movzbl (%rdi,%rdx,1),%eax
   0x0000000000049fe8 <+40>:    movzbl (%rsi,%rdx,1),%ecx
   0x0000000000049fec <+44>:    movzbl (%r8,%rax,1),%eax
   0x0000000000049ff1 <+49>:    movzbl (%r8,%rcx,1),%ecx
   0x0000000000049ff6 <+54>:    cmp    %ecx,%eax
   0x0000000000049ff8 <+56>:    jne    0x49ffe <apr_cstr_casecmp+62>
   0x0000000000049ffa <+58>:    test   %eax,%eax
   0x0000000000049ffc <+60>:    jne    0x49fe0 <apr_cstr_casecmp+32>
   0x0000000000049ffe <+62>:    sub    %ecx,%eax
   0x000000000004a000 <+64>:    ret   
End of assembler dump.

[2] apr_cstr_casecmp() before this commit:
Dump of assembler code for function apr_cstr_casecmp:
   0x000000000004a000 <+0>:     movzbl (%rdi),%eax
   0x000000000004a003 <+3>:     movzbl (%rsi),%edx
   0x000000000004a006 <+6>:     lea    0x3d533(%rip),%r8        # 0x87540 <ucharmap>
   0x000000000004a00d <+13>:    mov    %rdi,%r9
   0x000000000004a010 <+16>:    mov    %rax,%rcx
   0x000000000004a013 <+19>:    movswl (%r8,%rdx,2),%edx
   0x000000000004a018 <+24>:    movswl (%r8,%rax,2),%eax
   0x000000000004a01d <+29>:    sub    %edx,%eax
   0x000000000004a01f <+31>:    jne    0x4a052 <apr_cstr_casecmp+82>
   0x000000000004a021 <+33>:    mov    $0x1,%edx
   0x000000000004a026 <+38>:    test   %ecx,%ecx
   0x000000000004a028 <+40>:    je     0x4a052 <apr_cstr_casecmp+82>
   0x000000000004a02a <+42>:    nopw   0x0(%rax,%rax,1)
   0x000000000004a030 <+48>:    movzbl (%r9,%rdx,1),%eax
   0x000000000004a035 <+53>:    movzbl (%rsi,%rdx,1),%ecx
   0x000000000004a039 <+57>:    add    $0x1,%rdx
   0x000000000004a03d <+61>:    mov    %rax,%rdi
   0x000000000004a040 <+64>:    movswl (%r8,%rcx,2),%ecx
   0x000000000004a045 <+69>:    movswl (%r8,%rax,2),%eax
   0x000000000004a04a <+74>:    sub    %ecx,%eax
   0x000000000004a04c <+76>:    jne    0x4a052 <apr_cstr_casecmp+82>
   0x000000000004a04e <+78>:    test   %edi,%edi
   0x000000000004a050 <+80>:    jne    0x4a030 <apr_cstr_casecmp+48>
   0x000000000004a052 <+82>:    ret   
End of assembler dump.



git-svn-id: https://svn.apache.org/repos/asf/apr/apr/trunk@1897102 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 16 insertions, 26 deletions

diff --git a/strings/apr_cstr.c b/strings/apr_cstr.c
index 7717c4406..8ee55b54b 100644
--- a/strings/apr_cstr.c
+++ b/strings/apr_cstr.c
@@ -197,7 +197,7 @@ APR_DECLARE(char *) apr_cstr_join(const apr_array_header_t *strings,
  * octets (such as extended latin alphabetics) are never case-folded.
  * NOTE: Other than Alpha A-Z/a-z, each code point is unique!
  */
-static const short ucharmap[] = {
+static const unsigned char ucharmap[256] = {
     0x0,  0x1,  0x2,  0x3,  0x4,  0x5,  0x6,  0x7,
     0x8,  0x9,  0xa,  0xb,  0xc,  0xd,  0xe,  0xf,
     0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
@@ -244,7 +244,7 @@ static const short ucharmap[] = {
  *
  * NOTE: Other than Alpha A-Z/a-z, each code point is unique!
  */
-static const short ucharmap[] = {
+static const unsigned char ucharmap[256] = {
     0x00, 0x01, 0x02, 0x03, 0x9C, 0x09, 0x86, 0x7F,
     0x97, 0x8D, 0x8E, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
     0x10, 0x11, 0x12, 0x13, 0x9D, 0x85, 0x08, 0x87,
@@ -282,36 +282,26 @@ static const short ucharmap[] = {
 
 APR_DECLARE(int) apr_cstr_casecmp(const char *s1, const char *s2)
 {
-    const unsigned char *str1 = (const unsigned char *)s1;
-    const unsigned char *str2 = (const unsigned char *)s2;
-    for (;;)
-    {
-        const int c1 = (int)(*str1);
-        const int c2 = (int)(*str2);
-        const int cmp = ucharmap[c1] - ucharmap[c2];
-        /* Not necessary to test for !c2, this is caught by cmp */
-        if (cmp || !c1)
-            return cmp;
-        str1++;
-        str2++;
+    apr_size_t i = 0;
+    for (;; ++i) {
+        const int c1 = ucharmap[(unsigned char)s1[i]];
+        const int c2 = ucharmap[(unsigned char)s2[i]];
+        /* Not necessary to test for !c2, this is caught by c1 != c2 */
+        if (c1 != c2 || !c1)
+            return c1 - c2;
     }
 }
 
 APR_DECLARE(int) apr_cstr_casecmpn(const char *s1, const char *s2,
                                    apr_size_t n)
 {
-    const unsigned char *str1 = (const unsigned char *)s1;
-    const unsigned char *str2 = (const unsigned char *)s2;
-    while (n--)
-    {
-        const int c1 = (int)(*str1);
-        const int c2 = (int)(*str2);
-        const int cmp = ucharmap[c1] - ucharmap[c2];
-        /* Not necessary to test for !c2, this is caught by cmp */
-        if (cmp || !c1)
-            return cmp;
-        str1++;
-        str2++;
+    apr_size_t i = 0;
+    for (; i < n; ++i) {
+        const int c1 = ucharmap[(unsigned char)s1[i]];
+        const int c2 = ucharmap[(unsigned char)s2[i]];
+        /* Not necessary to test for !c2, this is caught by c1 != c2 */
+        if (c1 != c2 || !c1)
+            return c1 - c2;
     }
     return 0;
 }