Hi,
This patch cleans up pre-checking of expand_block_compare. It does
1. Assert only P7 above can enter this function as it's already guard
by the expand.
2. Return false when optimizing for size.
3. Remove P7 CPU test as only P7 above can enter this function and P7
LE is excluded by targetm.slow_unaligned_access.
Bootstrapped and tested on x86 and powerpc64-linux BE and LE with no
regressions. Is this OK for trunk?
Thanks
Gui Haochen
ChangeLog
rs6000: Clean up pre-checking of expand_block_compare
gcc/
* gcc/config/rs6000/rs6000-string.cc (expand_block_compare): Assert
only P7 above can enter this function. Return false when it's
optimized for size. Remove P7 CPU test as only P7 above can enter
this function and P7 LE is excluded by the checking of
targetm.slow_unaligned_access on word_mode.
gcc/testsuite/
* gcc.target/powerpc/memcmp_for_size.c: New.
patch.diff
diff --git a/gcc/config/rs6000/rs6000-string.cc
b/gcc/config/rs6000/rs6000-string.cc
index d4030854b2a..dff69e90d0c 100644
--- a/gcc/config/rs6000/rs6000-string.cc
+++ b/gcc/config/rs6000/rs6000-string.cc
@@ -1946,6 +1946,15 @@ expand_block_compare_gpr(unsigned HOST_WIDE_INT bytes,
unsigned int base_align,
bool
expand_block_compare (rtx operands[])
{
+ gcc_assert (TARGET_POPCNTD);
+
+ if (optimize_insn_for_size_p ())
+ return false;
+
+ /* Allow this param to shut off all expansion. */
+ if (rs6000_block_compare_inline_limit == 0)
+ return false;
+
rtx target = operands[0];
rtx orig_src1 = operands[1];
rtx orig_src2 = operands[2];
@@ -1959,23 +1968,9 @@ expand_block_compare (rtx operands[])
if (TARGET_32BIT && TARGET_POWERPC64)
return false;
- bool isP7 = (rs6000_tune == PROCESSOR_POWER7);
-
- /* Allow this param to shut off all expansion. */
- if (rs6000_block_compare_inline_limit == 0)
- return false;
-
- /* targetm.slow_unaligned_access -- don't do unaligned stuff.
- However slow_unaligned_access returns true on P7 even though the
- performance of this code is good there. */
- if (!isP7
- && (targetm.slow_unaligned_access (word_mode, MEM_ALIGN (orig_src1))
- || targetm.slow_unaligned_access (word_mode, MEM_ALIGN (orig_src2))))
- return false;
-
- /* Unaligned l*brx traps on P7 so don't do this. However this should
- not affect much because LE isn't really supported on P7 anyway. */
- if (isP7 && !BYTES_BIG_ENDIAN)
+ /* targetm.slow_unaligned_access -- don't do unaligned stuff. */
+ if (targetm.slow_unaligned_access (word_mode, MEM_ALIGN (orig_src1))
+ || targetm.slow_unaligned_access (word_mode, MEM_ALIGN (orig_src2)))
return false;
/* If this is not a fixed size compare, try generating loop code and
@@ -2023,14 +2018,6 @@ expand_block_compare (rtx operands[])
if (!IN_RANGE (bytes, 1, max_bytes))
return expand_compare_loop (operands);
- /* The code generated for p7 and older is not faster than glibc
- memcmp if alignment is small and length is not short, so bail
- out to avoid those conditions. */
- if (!TARGET_EFFICIENT_UNALIGNED_FIXEDPOINT
- && ((base_align == 1 && bytes > 16)
- || (base_align == 2 && bytes > 32)))
- return false;
-
rtx final_label = NULL;
if (use_vec)
diff --git a/gcc/testsuite/gcc.target/powerpc/memcmp_for_size.c
b/gcc/testsuite/gcc.target/powerpc/memcmp_for_size.c
new file mode 100644
index 00000000000..c7e853ad593
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/memcmp_for_size.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+/* { dg-final { scan-assembler-times {\mb[l]? memcmp\M} 1 } } */
+
+int foo (const char* s1, const char* s2)
+{
+ return __builtin_memcmp (s1, s2, 4);
+}
