Combine will fold immediate -1 differently than the other
*cmp*_carryinC* patterns. In this case we can use adcs
with an xzr input, and it occurs frequently when comparing
128-bit values to small negative constants.
* config/aarch64/aarch64.md (<su>cmp<GPI>_carryinC_m2): New.
---
gcc/config/aarch64/aarch64.md | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 9b1c3f797f9..076158b0071 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -3452,6 +3452,7 @@
""
)
+;; Substituting zero into the first input operand.
(define_insn "*usub<GPI:mode>3_carryinC_z1"
[(set (reg:CC CC_REGNUM)
(compare:CC
@@ -3482,6 +3483,7 @@
[(set_attr "type" "adc_reg")]
)
+;; Substituting zero into the second input operand.
(define_insn "*usub<GPI:mode>3_carryinC_z2"
[(set (reg:CC CC_REGNUM)
(compare:CC
@@ -3508,6 +3510,19 @@
[(set_attr "type" "adc_reg")]
)
+;; Substituting -1 into the second input operand.
+(define_insn "*<ANY_EXTEND:su>cmp<GPI:mode>3_carryinC_m2"
+ [(set (reg:CC CC_REGNUM)
+ (compare:CC
+ (neg:<DWI>
+ (match_operand:<DWI> 1 "aarch64_carry_operation" ""))
+ (ANY_EXTEND:<DWI>
+ (match_operand:GPI 0 "register_operand" "r"))))]
+ ""
+ "adcs\\t<w>zr, %<w>0, <w>zr"
+ [(set_attr "type" "adc_reg")]
+)
+
(define_insn "*usub<GPI:mode>3_carryinC"
[(set (reg:CC CC_REGNUM)
(compare:CC
--
2.20.1
