Hi,
This patch adds a combine pattern for "CA minus one". As CA only has two
values (0 or 1), we could convert following pattern
(sign_extend:DI (plus:SI (reg:SI 98 ca)
(const_int -1 [0xffffffffffffffff]))))
to
(plus:DI (reg:DI 98 ca)
(const_int -1 [0xffffffffffffffff])))
With this patch, one unnecessary sign extend is eliminated.
Bootstrapped and tested on powerpc64-linux BE and LE with no regressions.
Is this okay for trunk? Any recommendations? Thanks a lot.
ChangeLog
2022-05-16 Haochen Gui <[email protected]>
gcc/
PR target/95737
* config/rs6000/rs6000.md (subfsi3_carry_in_xx_64): New.
gcc/testsuite/
PR target/95737
* gcc.target/powerpc/pr95737.c: New.
patch.diff
diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index 64049a6e521..b97ac453fc0 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -2353,6 +2353,19 @@ (define_insn "subf<mode>3_carry_in_xx"
"subfe %0,%0,%0"
[(set_attr "type" "add")])
+(define_insn_and_split "*subfsi3_carry_in_xx_64"
+ [(set (match_operand:DI 0 "gpc_reg_operand" "=r")
+ (sign_extend:DI (plus:SI (reg:SI CA_REGNO)
+ (const_int -1))))]
+ "TARGET_POWERPC64"
+ "#"
+ ""
+ [(parallel [(set (match_dup 0)
+ (plus:DI (reg:DI CA_REGNO)
+ (const_int -1)))
+ (clobber (reg:DI CA_REGNO))])]
+ ""
+)
(define_insn "@neg<mode>2"
[(set (match_operand:GPR 0 "gpc_reg_operand" "=r")
diff --git a/gcc/testsuite/gcc.target/powerpc/pr95737.c
b/gcc/testsuite/gcc.target/powerpc/pr95737.c
new file mode 100644
index 00000000000..30f0f819393
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr95737.c
@@ -0,0 +1,11 @@
+/* PR target/95737 */
+/* { dg-do compile } */
+/* Disable isel for P9 and later */
+/* { dg-options "-O2 -mno-isel" } */
+/* { dg-final { scan-assembler-not {\mextsw\M} } } */
+
+
+unsigned long negativeLessThan (unsigned long a, unsigned long b)
+{
+ return -(a < b);
+}
