[PATCH 2/5] [RISC-V] Generate Zicond instruction for basic semantics

This patch completes the recognition of the basic semantics
defined in the spec, namely:

Conditional zero, if condition is equal to zero
  rd = (rs2 == 0) ? 0 : rs1
Conditional zero, if condition is non zero
  rd = (rs2 != 0) ? 0 : rs1

gcc/ChangeLog:

	* config/riscv/riscv.md: Include zicond.md
	* config/riscv/zicond.md: New file.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/zicond-primitiveSemantics.c: New test.

	Co-authored-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
	Co-authored-by: Raphael Zinsly <rzinsly@ventanamicro.com>
	Co-authored-by: Jeff Law <jlaw@ventanamicro.com>

3 files changed, 134 insertions, 0 deletions

diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index 24515bc..8d8fc93 100644
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -3319,3 +3319,4 @@
 (include "sifive-7.md")
 (include "thead.md")
 (include "vector.md")
+(include "zicond.md")
diff --git a/gcc/config/riscv/zicond.md b/gcc/config/riscv/zicond.md
new file mode 100644
index 0000000..723a224
--- /dev/null
+++ b/gcc/config/riscv/zicond.md
@@ -0,0 +1,84 @@
+;; Machine description for the RISC-V Zicond extension
+;; Copyright (C) 2022-23 Free Software Foundation, Inc.
+
+;; This file is part of GCC.
+
+;; GCC is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 3, or (at your option)
+;; any later version.
+
+;; GCC is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GCC; see the file COPYING3.  If not see
+;; <http://www.gnu.org/licenses/>.
+
+(define_code_iterator eq_or_ne [eq ne])
+(define_code_attr eqz [(eq "nez") (ne "eqz")])
+(define_code_attr nez [(eq "eqz") (ne "nez")])
+
+;; Zicond
+(define_insn "*czero.<eqz>.<GPR:mode><ANYI:mode>"
+  [(set (match_operand:GPR 0 "register_operand"                      "=r")
+        (if_then_else:GPR (eq_or_ne (match_operand:ANYI 1 "register_operand" "r")
+                                    (const_int 0))
+                          (match_operand:GPR 2 "register_operand"    "r")
+                          (const_int 0)))]
+  "TARGET_ZICOND"
+  "czero.<eqz>\t%0,%2,%1"
+)
+
+(define_insn "*czero.<nez>.<GPR:mode><ANYI:mode>"
+  [(set (match_operand:GPR 0 "register_operand"                     "=r")
+        (if_then_else:GPR (eq_or_ne (match_operand:ANYI 1 "register_operand" "r")
+                                    (const_int 0))
+                          (const_int 0)
+                          (match_operand:GPR 2 "register_operand"   "r")))]
+  "TARGET_ZICOND"
+  "czero.<nez>\t%0,%2,%1"
+)
+
+;; Special optimization under eq/ne in primitive semantics
+(define_insn "*czero.eqz.<GPR:mode><ANYI:mode>.opt1"
+  [(set (match_operand:GPR 0 "register_operand"                   "=r")
+        (if_then_else:GPR (eq (match_operand:ANYI 1 "register_operand" "r")
+                              (const_int 0))
+                          (match_operand:GPR 2 "register_operand" "1")
+                          (match_operand:GPR 3 "register_operand" "r")))]
+  "TARGET_ZICOND && rtx_equal_p (operands[1], operands[2])"
+  "czero.eqz\t%0,%3,%1"
+)
+
+(define_insn "*czero.eqz.<GPR:mode><ANYI:mode>.opt2"
+  [(set (match_operand:GPR 0 "register_operand"                   "=r")
+        (if_then_else:GPR (eq (match_operand:ANYI 1 "register_operand" "r")
+                              (const_int 0))
+                          (match_operand:GPR 2 "register_operand" "r")
+                          (match_operand:GPR 3 "register_operand" "1")))]
+  "TARGET_ZICOND && rtx_equal_p (operands[1],  operands[3])"
+  "czero.nez\t%0,%2,%1"
+)
+
+(define_insn "*czero.nez.<GPR:mode><ANYI:mode>.opt3"
+  [(set (match_operand:GPR 0 "register_operand"                   "=r")
+        (if_then_else:GPR (ne (match_operand:ANYI 1 "register_operand" "r")
+                              (const_int 0))
+                          (match_operand:GPR 2 "register_operand" "r")
+                          (match_operand:GPR 3 "register_operand" "1")))]
+  "TARGET_ZICOND && rtx_equal_p (operands[1], operands[3])"
+  "czero.eqz\t%0,%2,%1"
+)
+
+(define_insn "*czero.nez.<GPR:mode><ANYI:mode>.opt4"
+  [(set (match_operand:GPR 0 "register_operand"                   "=r")
+        (if_then_else:GPR (ne (match_operand:ANYI 1 "register_operand" "r")
+                              (const_int 0))
+                          (match_operand:GPR 2 "register_operand" "1")
+                          (match_operand:GPR 3 "register_operand" "r")))]
+  "TARGET_ZICOND && rtx_equal_p (operands[1], operands[2])"
+  "czero.nez\t%0,%3,%1"
+)
diff --git a/gcc/testsuite/gcc.target/riscv/zicond-primitiveSemantics.c b/gcc/testsuite/gcc.target/riscv/zicond-primitiveSemantics.c
new file mode 100644
index 0000000..76c5019
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zicond-primitiveSemantics.c
@@ -0,0 +1,49 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc_zicond -mabi=lp64d" { target { rv64 } } } */
+/* { dg-options "-march=rv32gc_zicond -mabi=ilp32f" { target { rv32 } } } */
+/* { dg-skip-if "" { *-*-* } {"-O0"} } */
+
+long primitiveSemantics_00(long a, long b) { return a == 0 ? 0 : b; }
+
+long primitiveSemantics_01(long a, long b) { return a != 0 ? 0 : b; }
+
+long primitiveSemantics_02(long a, long b) { return a == 0 ? b : 0; }
+
+long primitiveSemantics_03(long a, long b) { return a != 0 ? b : 0; }
+
+long primitiveSemantics_04(long a, long b) {
+  if (a)
+    b = 0;
+  return b;
+}
+
+long primitiveSemantics_05(long a, long b) {
+  if (!a)
+    b = 0;
+  return b;
+}
+
+int primitiveSemantics_06(int a, int b) { return a == 0 ? 0 : b; }
+
+int primitiveSemantics_07(int a, int b) { return a != 0 ? 0 : b; }
+
+int primitiveSemantics_08(int a, int b) { return a == 0 ? b : 0; }
+
+int primitiveSemantics_09(int a, int b) { return a != 0 ? b : 0; }
+
+int primitiveSemantics_10(int a, int b) {
+  if (a)
+    b = 0;
+  return b;
+}
+
+int primitiveSemantics_11(int a, int b) {
+  if (!a)
+    b = 0;
+  return b;
+}
+
+/* { dg-final { scan-assembler-times "czero.eqz" 6 } } */
+/* { dg-final { scan-assembler-times "czero.nez" 6 } } */
+/* { dg-final { scan-assembler-not "beq" } } */
+/* { dg-final { scan-assembler-not "bne" } } */