[PATCH v3] RISC-V: Add split pattern to generate SFB instructions. [PR113095]

Since the match.pd transforms (zero_one == 0) ? y : z <op> y,
into ((typeof(y))zero_one * z) <op> y. Add splitters to recongize
this expression to generate SFB instructions.

gcc/ChangeLog:
	PR target/113095
	* config/riscv/sfb.md: New splitters to rewrite single bit
	sign extension as the condition to SFB instructions.

gcc/testsuite/ChangeLog:
	* gcc.target/riscv/sfb.c: New test.
	* gcc.target/riscv/pr113095.c: New test.

gcc/config/riscv/sfb.md

@@ -35,3 +35,35 @@
   [(set_attr "length" "8")
    (set_attr "type" "sfb_alu")
    (set_attr "mode" "<GPR:MODE>")])
+
+;; Combine creates this form ((typeof(y))zero_one * z) <op> y
+;; for SiFive short forward branches.
+
+(define_split
+  [(set (match_operand:X 0 "register_operand")
+	(and:X (sign_extract:X (match_operand:X 1 "register_operand")
+			       (const_int 1)
+			       (match_operand 2 "immediate_operand"))
+	       (match_operand:X 3 "register_operand")))
+   (clobber (match_operand:X 4 "register_operand"))]
+  "TARGET_SFB_ALU"
+  [(set (match_dup 4) (zero_extract:X (match_dup 1) (const_int 1) (match_dup 2)))
+   (set (match_dup 0) (if_then_else:X (ne (match_dup 4) (const_int 0))
+				      (match_dup 3)
+				      (const_int 0)))])
+
+(define_split
+  [(set (match_operand:X 0 "register_operand")
+	(and:X (sign_extract:X (match_operand:X 1 "register_operand")
+			       (const_int 1)
+			       (match_operand 2 "immediate_operand"))
+	       (match_operand:X 3 "register_operand")))
+   (clobber (match_operand:X 4 "register_operand"))]
+  "TARGET_SFB_ALU && (UINTVAL (operands[2]) < 11)"
+  [(set (match_dup 4) (and:X (match_dup 1) (match_dup 2)))
+   (set (match_dup 0) (if_then_else:X (ne (match_dup 4) (const_int 0))
+				      (match_dup 3)
+				      (const_int 0)))]
+{
+  operands[2] = GEN_INT (1 << UINTVAL(operands[2]));
+})

gcc/testsuite/gcc.target/riscv/pr113095.c

@@ -0,0 +1,21 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -march=rv32gc -mabi=ilp32d -mtune=sifive-7-series" { target { rv32 } } } */
+/* { dg-options "-O2 -march=rv64gc -mabi=lp64d -mtune=sifive-7-series" {target { rv64 } } } */
+
+extern void abort (void);
+extern void exit (int);
+
+unsigned short __attribute__ ((noinline, noclone))
+foo (unsigned short x) {
+  if (x == 1)
+    x ^= 0x4002;
+
+  return x;
+}
+
+int main () {
+  if (foo(1) != 0x4003)
+    abort ();
+
+  exit(0);
+}

gcc/testsuite/gcc.target/riscv/sfb.c

@@ -0,0 +1,24 @@
+//* { dg-do compile } */
+/* { dg-options "-O2 -march=rv32gc -mabi=ilp32d -mtune=sifive-7-series" } */
+
+int f1(unsigned int x, unsigned int y, unsigned int z)
+{
+  return ((x & 1) == 0) ? y : z ^ y;
+}
+
+int f2(unsigned int x, unsigned int y, unsigned int z)
+{
+  return ((x & 1) != 0) ? z ^ y : y;
+}
+
+int f3(unsigned int x, unsigned int y, unsigned int z)
+{
+  return ((x & 1) == 0) ? y : z | y;
+}
+
+int f4(unsigned int x, unsigned int y, unsigned int z)
+{
+  return ((x & 1) != 0) ? z | y : y;
+}
+/* { dg-final { scan-assembler-times "bne" 4 } } */
+/* { dg-final { scan-assembler-times "movcc" 4 } } */