[RFC PATCH v1 05/10] RISC-V: Support noce_try_store_flag_mask as czero.eqz/czero.nez

[Philipp Tomsich <philipp.tomsich@vrull.eu>]

When if-conversion in noce_try_store_flag_mask starts the sequence off
with an order-operator, our patterns for czero.eqz/nez will receive
the result of the order-operator as a register argument; consequently,
they can't know that the result will be either 1 or 0.

To convey this information (and make czero.eqz/nez applicable), we
wrap the result of the order-operator in a eq/ne against (const_int 0).
This commit adds the split pattern to handle these cases.

During if-conversion, if noce_try_store_flag_mask succeeds, we may see
    if (cur < next) {
	next = 0;
    }
transformed into
   27: r82:SI=ltu(r76:DI,r75:DI)
      REG_DEAD r76:DI
   28: r81:SI=r82:SI^0x1
      REG_DEAD r82:SI
   29: r80:DI=zero_extend(r81:SI)
      REG_DEAD r81:SI

This currently escapes the combiner, as RISC-V does not have a pattern
to apply the 'slt' instruction to 'geu' verbs.  By adding a pattern in
this commit, we match such cases.

gcc/ChangeLog:

	* config/riscv/predicates.md (anyge_operator): Define.
	(anygt_operator): Same.
	(anyle_operator): Same.
	(anylt_operator): Same.
	* config/riscv/riscv.md: Helpers for ge(u) & le(u).
	* config/riscv/zicond.md: Add split to wrap an an
	order-operator suitably for generating czero.eqz/nez

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/zicond-le-02.c: New test.
	* gcc.target/riscv/zicond-lt-03.c: New test.

Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
---

 gcc/config/riscv/predicates.md                | 12 +++++
 gcc/config/riscv/riscv.md                     | 26 ++++++++++
 gcc/config/riscv/zicond.md                    | 50 +++++++++++++++++++
 gcc/testsuite/gcc.target/riscv/zicond-le-02.c | 11 ++++
 gcc/testsuite/gcc.target/riscv/zicond-lt-03.c | 16 ++++++
 5 files changed, 115 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/riscv/zicond-le-02.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/zicond-lt-03.c

diff --git a/gcc/config/riscv/predicates.md b/gcc/config/riscv/predicates.md
index 034d088c656..6b6f867824e 100644
--- a/gcc/config/riscv/predicates.md
+++ b/gcc/config/riscv/predicates.md
@@ -204,6 +204,18 @@ (define_predicate "modular_operator"
 (define_predicate "equality_operator"
   (match_code "eq,ne"))
 
+(define_predicate "anyge_operator"
+  (match_code "ge,geu"))
+
+(define_predicate "anygt_operator"
+  (match_code "gt,gtu"))
+
+(define_predicate "anyle_operator"
+  (match_code "le,leu"))
+
+(define_predicate "anylt_operator"
+  (match_code "lt,ltu"))
+
 (define_predicate "order_operator"
   (match_code "eq,ne,lt,ltu,le,leu,ge,geu,gt,gtu"))
 
diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index 7c632bb4d65..6f255a80379 100644
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -2668,6 +2668,19 @@ (define_insn "*sge<u>_<X:mode><GPR:mode>"
   [(set_attr "type" "slt")
    (set_attr "mode" "<X:MODE>")])
 
+(define_split
+  [(set (match_operand:GPR 0 "register_operand")
+	(match_operator:GPR 1 "anyle_operator"
+	       [(match_operand:X 2 "register_operand")
+		(match_operand:X 3 "register_operand")]))]
+  "TARGET_ZICOND"
+  [(set (match_dup 0) (match_dup 4))
+   (set (match_dup 0) (eq:GPR (match_dup 0) (const_int 0)))]
+ {
+  operands[4] = gen_rtx_fmt_ee (GET_CODE (operands[1]) == LE ? LT : LTU,
+				<GPR:MODE>mode, operands[3], operands[2]);
+ })
+
 (define_insn "*slt<u>_<X:mode><GPR:mode>"
   [(set (match_operand:GPR           0 "register_operand" "= r")
 	(any_lt:GPR (match_operand:X 1 "register_operand" "  r")
@@ -2689,6 +2702,19 @@ (define_insn "*sle<u>_<X:mode><GPR:mode>"
   [(set_attr "type" "slt")
    (set_attr "mode" "<X:MODE>")])
 
+(define_split
+  [(set (match_operand:GPR 0 "register_operand")
+	(match_operator:GPR 1 "anyge_operator"
+	       [(match_operand:X 2 "register_operand")
+		(match_operand:X 3 "register_operand")]))]
+  "TARGET_ZICOND"
+  [(set (match_dup 0) (match_dup 4))
+   (set (match_dup 0) (eq:GPR (match_dup 0) (const_int 0)))]
+{
+  operands[4] = gen_rtx_fmt_ee (GET_CODE (operands[1]) == GE ? LT : LTU,
+				<GPR:MODE>mode, operands[2], operands[3]);
+})
+
 ;;
 ;;  ....................
 ;;
diff --git a/gcc/config/riscv/zicond.md b/gcc/config/riscv/zicond.md
index 19d0b35585b..9d1ce067150 100644
--- a/gcc/config/riscv/zicond.md
+++ b/gcc/config/riscv/zicond.md
@@ -48,3 +48,53 @@ (define_split
   if (!rtx_equal_p (operands[0], operands[2]))
      operands[4] = operands[0];
 })
+
+;; Make order operators digestible to the vt.maskc<n> logic by
+;; wrapping their result in a comparison against (const_int 0).
+
+;; "a >= b" is "!(a < b)"
+(define_split
+  [(set (match_operand:X 0 "register_operand")
+	(and:X (neg:X (match_operator:X 1 "anyge_operator"
+			     [(match_operand:X 2 "register_operand")
+			      (match_operand:X 3 "arith_operand")]))
+	       (match_operand:X 4 "register_operand")))
+   (clobber (match_operand:X 5 "register_operand"))]
+  "TARGET_ZICOND"
+  [(set (match_dup 5) (match_dup 6))
+   (set (match_dup 0) (and:X (neg:X (eq:X (match_dup 5) (const_int 0)))
+			     (match_dup 4)))]
+{
+  operands[6] = gen_rtx_fmt_ee (GET_CODE (operands[1]) == GE ? LT : LTU,
+				<X:MODE>mode, operands[2], operands[3]);
+})
+
+;; "a > b"
+(define_split
+  [(set (match_operand:X 0 "register_operand")
+	(and:X (neg:X (match_operator:X 1 "anygt_operator"
+			     [(match_operand:X 2 "register_operand")
+			      (match_operand:X 3 "arith_operand")]))
+	       (match_operand:X 4 "register_operand")))
+   (clobber (match_operand:X 5 "register_operand"))]
+  "TARGET_ZICOND"
+  [(set (match_dup 5) (match_dup 1))
+   (set (match_dup 0) (and:X (neg:X (ne:X (match_dup 5) (const_int 0)))
+			     (match_dup 4)))])
+
+;; "a <= b" is "!(a > b)"
+(define_split
+  [(set (match_operand:X 0 "register_operand")
+	(and:X (neg:X (match_operator:X 1 "anyle_operator"
+			     [(match_operand:X 2 "register_operand")
+			      (match_operand:X 3 "arith_operand")]))
+	       (match_operand:X 4 "register_operand")))
+   (clobber (match_operand:X 5 "register_operand"))]
+  "TARGET_ZICOND"
+  [(set (match_dup 5) (match_dup 6))
+   (set (match_dup 0) (and:X (neg:X (eq:X (match_dup 5) (const_int 0)))
+			     (match_dup 4)))]
+{
+  operands[6] = gen_rtx_fmt_ee (GET_CODE (operands[1]) == LE ? GT : GTU,
+				<X:MODE>mode, operands[2], operands[3]);
+})
diff --git a/gcc/testsuite/gcc.target/riscv/zicond-le-02.c b/gcc/testsuite/gcc.target/riscv/zicond-le-02.c
new file mode 100644
index 00000000000..32844bc0278
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zicond-le-02.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc_zicond -mabi=lp64" } */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-Og" "-O1" "-Os" "-Oz"  } } */
+
+long long le2 (long long a, long long b, long long c)
+{
+  return (a <= c) ? b : 0;
+}
+
+/* { dg-final { scan-assembler-times "sgt\t" 1 } } */
+/* { dg-final { scan-assembler-times "czero.nez\t" 1 } } */
diff --git a/gcc/testsuite/gcc.target/riscv/zicond-lt-03.c b/gcc/testsuite/gcc.target/riscv/zicond-lt-03.c
new file mode 100644
index 00000000000..1c4f0d6ba10
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zicond-lt-03.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc_zicond -mabi=lp64 -mbranch-cost=4" } */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-Og" "-O1" "-Os" "-Oz"  } } */
+
+long long sink (long long);
+
+long long lt3 (long long a, long long b)
+{
+  if (a < b)
+    b = 0;
+
+  return sink(b);
+}
+
+/* { dg-final { scan-assembler-times "slt\t" 1 } } */
+/* { dg-final { scan-assembler-times "czero.nez\t" 1 } } */
-- 
2.34.1