Use carry flag from addition to implement GEU/LTU compares
with negated operand, so e.g.
~x < y
compiles to:
addq %rsi, %rdi
setc %al
instead of:
notq %rdi
cmpq %rsi, %rdi
setb %al
2020-05-06 Uroš Bizjak <ubiz...@gmail.com>
PR target/94913
* config/i386/predicates.md (add_comparison_operator): New predicate.
* config/i386/i386.md (compare->add splitter): New splitters.
testsuite/ChangeLog:
2020-05-06 Uroš Bizjak <ubiz...@gmail.com>
PR target/94913
* gcc.target/i386/pr94913-1.c: New test.
* gcc.target/i386/pr94913-2.c: Ditto.
Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
Committed to mainline.
Uros.
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 911ef7a6c4c..5fe851e0312 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -12324,6 +12324,21 @@
;; Store-flag instructions.
+(define_split
+ [(set (match_operand:QI 0 "nonimmediate_operand")
+ (match_operator:QI 1 "add_comparison_operator"
+ [(not:SWI (match_operand:SWI 2 "register_operand"))
+ (match_operand:SWI 3 "nonimmediate_operand")]))]
+ ""
+ [(parallel
+ [(set (reg:CCC FLAGS_REG)
+ (compare:CCC
+ (plus:SWI (match_dup 2) (match_dup 3))
+ (match_dup 2)))
+ (clobber (scratch:SWI))])
+ (set (match_dup 0)
+ (match_op_dup 1 [(reg:CCC FLAGS_REG) (const_int 0)]))])
+
(define_split
[(set (match_operand:QI 0 "nonimmediate_operand")
(match_operator:QI 1 "shr_comparison_operator"
@@ -12518,6 +12533,26 @@
;; Basic conditional jump instructions.
+(define_split
+ [(set (pc)
+ (if_then_else
+ (match_operator 1 "add_comparison_operator"
+ [(not:SWI (match_operand:SWI 2 "register_operand"))
+ (match_operand:SWI 3 "nonimmediate_operand")])
+ (label_ref (match_operand 0))
+ (pc)))]
+ ""
+ [(parallel
+ [(set (reg:CCC FLAGS_REG)
+ (compare:CCC
+ (plus:SWI (match_dup 2) (match_dup 3))
+ (match_dup 2)))
+ (clobber (scratch:SWI))])
+ (set (pc)
+ (if_then_else (match_op_dup 1 [(reg:CCC FLAGS_REG) (const_int 0)])
+ (label_ref (match_operand 0))
+ (pc)))])
+
(define_split
[(set (pc)
(if_then_else
diff --git a/gcc/config/i386/predicates.md b/gcc/config/i386/predicates.md
index 1a5e2210eca..8d8bcb1a765 100644
--- a/gcc/config/i386/predicates.md
+++ b/gcc/config/i386/predicates.md
@@ -1293,6 +1293,9 @@
(define_predicate "shr_comparison_operator"
(match_code "gtu,leu"))
+(define_predicate "add_comparison_operator"
+ (match_code "geu,ltu"))
+
;; Return true if OP is a valid comparison operator in valid mode.
(define_predicate "ix86_comparison_operator"
(match_operand 0 "comparison_operator")
diff --git a/gcc/testsuite/gcc.target/i386/pr94913-1.c
b/gcc/testsuite/gcc.target/i386/pr94913-1.c
new file mode 100644
index 00000000000..f21032d4522
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr94913-1.c
@@ -0,0 +1,21 @@
+/* PR target/94913 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+char fooc (unsigned char x, unsigned char y)
+{
+ return (unsigned char) ~x < y;
+}
+
+short foos (unsigned short x, unsigned short y)
+{
+ return (unsigned short) ~x < y;
+}
+
+long fooi (unsigned long x, unsigned long y)
+{
+ return (unsigned long) ~x < y;
+}
+
+/* { dg-final { scan-assembler-not "cmp" } } */
+/* { dg-final { scan-assembler-times "add" 3 } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr94913-2.c
b/gcc/testsuite/gcc.target/i386/pr94913-2.c
new file mode 100644
index 00000000000..22bca2bf27b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr94913-2.c
@@ -0,0 +1,24 @@
+/* PR target/94913 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+void f1 (void);
+void f2 (void);
+
+void fooc (unsigned char x, unsigned char y)
+{
+ if ((unsigned char) ~x < y) f1 (); else f2 ();
+}
+
+void foos (unsigned short x, unsigned short y)
+{
+ if ((unsigned short) ~x < y) f1 (); else f2 ();
+}
+
+void fooi (unsigned long x, unsigned long y)
+{
+ if ((unsigned long) ~x < y) f1 (); else f2 ();
+}
+
+/* { dg-final { scan-assembler-not "cmp" } } */
+/* { dg-final { scan-assembler-times "add" 3 } } */
