Modified: trunk/Source/WTF/ChangeLog (145948 => 145949)
--- trunk/Source/WTF/ChangeLog 2013-03-15 22:05:36 UTC (rev 145948)
+++ trunk/Source/WTF/ChangeLog 2013-03-15 22:09:25 UTC (rev 145949)
@@ -1,5 +1,24 @@
2013-03-15 Benjamin Poulain <bpoul...@apple.com>
+ [iOS] Update StringImpl's equal to have a single version on all supported Apple CPUs
+ https://bugs.webkit.org/show_bug.cgi?id=112400
+
+ Reviewed by Michael Saboff.
+
+ * wtf/text/StringImpl.h:
+ (WTF::equal):
+ Tweak the code to make it work on older Apple CPUs:
+ -Use external "ouput" variable instead of the registers R9 and R12. This gets rid
+ of some register pressure previously imposed on the compiler. (Clang nicely
+ choose R9 and R12 when needed, following iOS ABI).
+ -Instead of using "R3" for storing the length / 4, update the length by -4 on
+ each iteration and work in the negative space for the tail. This frees one register
+ which is then used for isEqual.
+ -Get rid of the unconditional branch from the loop. By using subs and working in the
+ negative space, we can test for the Carry flag to jump back to the next LDR.
+
+2013-03-15 Benjamin Poulain <bpoul...@apple.com>
+
[iOS] Fix the length pass to memcmp in the fallback versions of String's equal
https://bugs.webkit.org/show_bug.cgi?id=112463
Modified: trunk/Source/WTF/wtf/text/StringImpl.h (145948 => 145949)
--- trunk/Source/WTF/wtf/text/StringImpl.h 2013-03-15 22:05:36 UTC (rev 145948)
+++ trunk/Source/WTF/wtf/text/StringImpl.h 2013-03-15 22:09:25 UTC (rev 145949)
@@ -917,43 +917,52 @@
return true;
}
-#elif CPU(APPLE_ARMV7S)
+#elif PLATFORM(IOS) && WTF_ARM_ARCH_AT_LEAST(7)
ALWAYS_INLINE bool equal(const LChar* a, const LChar* b, unsigned length)
{
bool isEqual = false;
- asm("lsr r3, %[length], #2\n"
+ uint32_t aValue;
+ uint32_t bValue;
+ asm("subs %[length], #4\n"
+ "blo 2f\n"
- "0:\n" // Tag 0 = Start of loop over 32 bits.
- "cbz r3, 2f\n"
- "ldr r9, [%[a]], #4\n"
- "sub r3, #1\n"
- "ldr r12, [%[b]], #4\n"
- "cmp r9, r12\n"
- "beq 0b\n"
- "b 66f\n"
+ "0:\n" // Label 0 = Start of loop over 32 bits.
+ "ldr %[aValue], [%[a]], #4\n"
+ "ldr %[bValue], [%[b]], #4\n"
+ "cmp %[aValue], %[bValue]\n"
+ "bne 66f\n"
+ "subs %[length], #4\n"
+ "bhs 0b\n"
- "2:\n" // Tag 2 = End of loop over 32 bits, check for pair of characters.
+ // At this point, length can be:
+ // -0: 00000000000000000000000000000000 (0 bytes left)
+ // -1: 11111111111111111111111111111111 (3 bytes left)
+ // -2: 11111111111111111111111111111110 (2 bytes left)
+ // -3: 11111111111111111111111111111101 (1 byte left)
+ // -4: 11111111111111111111111111111100 (length was 0)
+ // The pointers are at the correct position.
+ "2:\n" // Label 2 = End of loop over 32 bits, check for pair of characters.
"tst %[length], #2\n"
"beq 1f\n"
- "ldrh r9, [%[a]], #2\n"
- "ldrh r12, [%[b]], #2\n"
- "cmp r9, r12\n"
+ "ldrh %[aValue], [%[a]], #2\n"
+ "ldrh %[bValue], [%[b]], #2\n"
+ "cmp %[aValue], %[bValue]\n"
"bne 66f\n"
- "1:\n" // Tag 1 = Check for a single character left.
+ "1:\n" // Label 1 = Check for a single character left.
"tst %[length], #1\n"
"beq 42f\n"
- "ldrb r9, [%[a]]\n"
- "ldrb r12, [%[b]]\n"
- "cmp r9, r12\n"
+ "ldrb %[aValue], [%[a]]\n"
+ "ldrb %[bValue], [%[b]]\n"
+ "cmp %[aValue], %[bValue]\n"
"bne 66f\n"
- "42:\n" // Tag 42 = Success.
+ "42:\n" // Label 42 = Success.
"mov %[isEqual], #1\n"
- "66:\n" // Tag 66 = End without changing isEqual to 1.
- : [isEqual]"+r"(isEqual), [a]"+r"(a), [b]"+r"(b)
- : [length]"r"(length)
- : "r3", "r9", "r12"
+ "66:\n" // Label 66 = End without changing isEqual to 1.
+ : [length]"+r"(length), [isEqual]"+r"(isEqual), [a]"+r"(a), [b]"+r"(b), [aValue]"+r"(aValue), [bValue]"+r"(bValue)
+ :
+ :
);
return isEqual;
}
@@ -962,16 +971,6 @@
{
return !memcmp(a, b, length * sizeof(UChar));
}
-#elif PLATFORM(IOS) && WTF_ARM_ARCH_AT_LEAST(7)
-ALWAYS_INLINE bool equal(const LChar* a, const LChar* b, unsigned length)
-{
- return !memcmp(a, b, length);
-}
-
-ALWAYS_INLINE bool equal(const UChar* a, const UChar* b, unsigned length)
-{
- return !memcmp(a, b, length * sizeof(UChar));
-}
#else
ALWAYS_INLINE bool equal(const LChar* a, const LChar* b, unsigned length)
{
