Hello!
Attached patch enables post-reload compare optimization pass for x86 targets.
As shown in following test, patch removes redundant compare:
--cut here--
int test(int a, int b)
{
int lt = a < b;
int eq = a == b;
if (lt)
return 1;
return eq;
}
--cut here--
gcc -O2 on x86_64, a cmove target:
test:
xorl %edx, %edx
cmpl %esi, %edi
movl $1, %eax
sete %dl
cmovge %edx, %eax
ret
gcc-O2 -fno-compare-elim:
test:
xorl %edx, %edx
cmpl %esi, %edi
movl $1, %eax
sete %dl
cmpl %esi, %edi
cmovge %edx, %eax
ret
2012-02-05 Uros Bizjak <ubiz...@gmail.com>
PR target/28685
* config/i386/i386.c (TARGET_FLAGS_REGNUM): New.
testsuite/ChangeLog:
PR target/28685
* gcc.target/i386/pr28685.c: New test.
The patch was tested on x86_64-pc-linux-gnu {,-m32}. The patch will be
committed to 4.8 once stage 1 opens.
Uros.
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 183904)
+++ config/i386/i386.c (working copy)
@@ -38685,6 +38685,9 @@
#undef TARGET_EXPAND_TO_RTL_HOOK
#define TARGET_EXPAND_TO_RTL_HOOK ix86_maybe_switch_abi
+#undef TARGET_FLAGS_REGNUM
+#define TARGET_FLAGS_REGNUM FLAGS_REG
+
#undef TARGET_LEGITIMATE_ADDRESS_P
#define TARGET_LEGITIMATE_ADDRESS_P ix86_legitimate_address_p
Index: testsuite/gcc.target/i386/pr28685.c
===================================================================
--- testsuite/gcc.target/i386/pr28685.c (revision 0)
+++ testsuite/gcc.target/i386/pr28685.c (revision 0)
@@ -0,0 +1,12 @@
+/* { dg-options "-O2" } */
+
+int test(int a, int b)
+{
+ int lt = a < b;
+ int eq = a == b;
+ if (lt)
+ return 1;
+ return eq;
+}
+
+/* { dg-final { scan-assembler-times "cmp" 1 } } */
