Doh! This time with the patch attached...
This patch resolves PR target/43892 (suboptimal add with carry) by adding
four new define_insn_and_split to the rs6000 backend, that all recognize
pairs of instructions where the first instruction sets the carry flag and
the second one consumes it. It also adds a commutative variant of
add<mode>3_carry_in_0 (aka "addze") to catch cases, not caught by recog's
insn canonicalization, where CA_REG appears first.
For the add32carry function in the original PR:
unsigned int add32carry(unsigned int sum, unsigned int x) {
unsigned int z = sum + x;
if (sum + x < x)
z++;
return z;
}
previously "-O2 -m32" would generate:
add32carry:
add 3,3,4
subfc 4,4,3
subfe 9,9,9
subf 3,9,3
blr
with this patch we now generate:
add32carry:
addc 3,3,4
addze 3,3
blr
And for the related examples in the new test case,
unsigned long add_leu(unsigned long a, unsigned long b, unsigned long c) {
return a + (b <= c);
}
unsigned long add_geu(unsigned long a, unsigned long b, unsigned long c) {
return a + (b >= c);
}
On powerpc64 with -O2 we'd previously generate:
add_leu:
subfc 4,4,5
subfe 9,9,9
addi 9,9,1
add 3,9,3
blr
add_geu:
subfc 5,5,4
subfe 9,9,9
addi 9,9,1
add 3,9,3
blr
but with this patch we now generate:
add_leu:
subfc 4,4,5
addze 3,3
blr
add_geu:
subfc 5,5,4
addze 3,3
blr
This patch has been tested on powerpc64-unknown-linux-gnu (many thanks to
gcc203.fsffrance.org on the GCC compile farm) with a make bootstrap and make
-k check with now new failures.
Ok for mainline?
2021-12-03 Roger Sayle <ro...@nextmovesoftware.com>
gcc/ChangeLog
PR target/43892
* config/rs6000/rs6000.md (*add<mode>3_carry_in_0_2): New
define_insn to recognize commutative form of add<mode>3_carry_in_0.
(*add<mode>3_geu, *add<mode>3_leu, *subf<mode>3_carry_in_xx_subf,
*add<mode>3_carry_in_addc): New define_insn_and_split patterns.
gcc/testsuite/ChangeLog
PR target/43892
* gcc.target/powerpc/addcmp.c: New test case.
* gcc.target/powerpc/pr43892.c: New test case.
Many thanks in advance.
Roger
--
diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index 6bec2bddbde..90c23556ccb 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -2067,6 +2067,16 @@
"addze %0,%1"
[(set_attr "type" "add")])
+;; Non-canonical form of add<mode>3_carry_in_0
+(define_insn "*add<mode>3_carry_in_0_2"
+ [(set (match_operand:GPR 0 "gpc_reg_operand" "=r")
+ (plus:GPR (reg:GPR CA_REGNO)
+ (match_operand:GPR 1 "gpc_reg_operand" "r")))
+ (clobber (reg:GPR CA_REGNO))]
+ ""
+ "addze %0,%1"
+ [(set_attr "type" "add")])
+
(define_insn "add<mode>3_carry_in_m1"
[(set (match_operand:GPR 0 "gpc_reg_operand" "=r")
(plus:GPR (plus:GPR (match_operand:GPR 1 "gpc_reg_operand" "r")
@@ -2078,6 +2088,95 @@
[(set_attr "type" "add")])
+;; PR target/43892 -> subf<mode>3_carry ; add<mode>3_carry_in_0
+(define_insn_and_split "*add<mode>3_geu"
+ [(set (match_operand:P 0 "gpc_reg_operand" "=r")
+ (plus:P (geu:P (match_operand:P 1 "gpc_reg_operand" "r")
+ (match_operand:P 2 "gpc_reg_operand" "r"))
+ (match_operand:P 3 "gpc_reg_operand" "r")))
+ (clobber (match_scratch:P 4 "=r"))
+ (clobber (reg:P CA_REGNO))]
+ ""
+ "#"
+ "&& 1"
+ [(const_int 0)]
+{
+ if (GET_CODE (operands[4]) == SCRATCH)
+ operands[4] = gen_reg_rtx (<MODE>mode);
+ emit_insn (gen_subf<mode>3_carry (operands[4], operands[1], operands[2]));
+ emit_insn (gen_add<mode>3_carry_in_0 (operands[0], operands[3]));
+ DONE;
+}
+ [(set_attr "type" "two")
+ (set_attr "length" "8")])
+
+;; PR target/43892 -> subf<mode>3_carry ; add<mode>3_carry_in_0
+(define_insn_and_split "*add<mode>3_leu"
+ [(set (match_operand:P 0 "gpc_reg_operand" "=r")
+ (plus:P (leu:P (match_operand:P 1 "gpc_reg_operand" "r")
+ (match_operand:P 2 "gpc_reg_operand" "r"))
+ (match_operand:P 3 "gpc_reg_operand" "r")))
+ (clobber (match_scratch:P 4 "=r"))
+ (clobber (reg:P CA_REGNO))]
+ ""
+ "#"
+ "&& 1"
+ [(const_int 0)]
+{
+ if (GET_CODE (operands[4]) == SCRATCH)
+ operands[4] = gen_reg_rtx (<MODE>mode);
+ emit_insn (gen_subf<mode>3_carry (operands[4], operands[2], operands[1]));
+ emit_insn (gen_add<mode>3_carry_in_0 (operands[0], operands[3]));
+ DONE;
+}
+ [(set_attr "type" "two")
+ (set_attr "length" "8")])
+
+;; PR target/43892 -> subf<mode>3_carry_in_xx ; subf<mode>3
+(define_insn_and_split "*subf<mode>3_carry_in_xx_subf"
+ [(set (match_operand:P 0 "gpc_reg_operand" "=r")
+ (plus:P (minus:P (match_operand:P 1 "gpc_reg_operand" "r")
+ (reg:P CA_REGNO))
+ (const_int 1)))
+ (clobber (match_scratch:P 2 "=r"))
+ (clobber (reg:P CA_REGNO))]
+ ""
+ "#"
+ "&& 1"
+ [(const_int 0)]
+{
+ if (GET_CODE (operands[2]) == SCRATCH)
+ operands[2] = gen_reg_rtx (<MODE>mode);
+ emit_insn (gen_subf<mode>3_carry_in_xx (operands[2]));
+ emit_insn (gen_sub<mode>3 (operands[0], operands[1], operands[2]));
+ DONE;
+}
+ [(set_attr "type" "two")
+ (set_attr "length" "8")])
+
+;; PR target/43892 -> add<mode>3_carry ; add<mode>3_carry_in_0
+(define_insn_and_split "*add<mode>3_carry_in_addc"
+ [(set (match_operand:P 0 "gpc_reg_operand" "=r")
+ (plus:P (plus:P
+ (ltu:P (plus:P (match_operand:P 1 "gpc_reg_operand" "r")
+ (match_operand:P 2 "gpc_reg_operand" "r"))
+ (match_dup 1))
+ (match_dup 2))
+ (match_dup 1)))
+ (clobber (reg:P CA_REGNO))]
+ ""
+ "#"
+ "&& 1"
+ [(const_int 0)]
+{
+ emit_insn (gen_add<mode>3_carry (operands[0], operands[1], operands[2]));
+ emit_insn (gen_add<mode>3_carry_in_0 (operands[0], operands[0]));
+ DONE;
+}
+ [(set_attr "type" "two")
+ (set_attr "length" "8")])
+
+
(define_expand "one_cmpl<mode>2"
[(set (match_operand:SDI 0 "gpc_reg_operand")
(not:SDI (match_operand:SDI 1 "gpc_reg_operand")))]
diff --git a/gcc/testsuite/gcc.target/powerpc/addcmp.c
b/gcc/testsuite/gcc.target/powerpc/addcmp.c
new file mode 100644
index 00000000000..6ca971bfc66
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/addcmp.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+unsigned long add_leu(unsigned long a, unsigned long b, unsigned long c) {
+ return a + (b <= c);
+}
+
+unsigned long add_geu(unsigned long a, unsigned long b, unsigned long c) {
+ return a + (b >= c);
+}
+
+/* { dg-final { scan-assembler-times "addze " 2 } } */
diff --git a/gcc/testsuite/gcc.target/powerpc/pr43892.c
b/gcc/testsuite/gcc.target/powerpc/pr43892.c
new file mode 100644
index 00000000000..f5d6b852c5f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr43892.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+unsigned long foo(unsigned long sum, unsigned long x)
+{
+ unsigned long z = sum + x;
+ if (sum + x < x)
+ z++;
+ return z;
+}
+
+/* { dg-final { scan-assembler "addze " } } */
