[to-be-committed] [RISC-V] Improve (1 << N) | C for rv64

Another improvement for generating Zbs instructions.

In this case we're looking at stuff like (1 << N) | C where N varies and C is a
single bit constant.

In this pattern the (1 << N) happens in SImode, but is zero extended out to
DImode before the bit manipulation.  The fact that we're modifying a DImode
object in the logical op is important as it means we don't have to worry about
whether or not the resulting value is sign extended from SI to DI.

This has run through Ventana's CI system.  I'll wait for it to roll through
pre-commit CI before moving forward.

gcc/
	* config/riscv/bitmanip.md ((1 << N) | C): New splitter for IOR/XOR
	of a single bit an a DImode object.

gcc/testsuite/

	* gcc.target/riscv/zbs-zext.c: New test.

2 files changed, 46 insertions, 0 deletions

diff --git a/gcc/config/riscv/bitmanip.md b/gcc/config/riscv/bitmanip.md
index 4ee413c..0d35fb7 100644
--- a/gcc/config/riscv/bitmanip.md
+++ b/gcc/config/riscv/bitmanip.md
@@ -627,6 +627,21 @@
   "bseti\t%0,%1,%S2"
   [(set_attr "type" "bitmanip")])
 
+;; We can easily handle zero extensions
+(define_split
+  [(set (match_operand:DI 0 "register_operand")
+    (any_or:DI (zero_extend:DI
+		 (ashift:SI (const_int 1)
+			    (match_operand:QI 1 "register_operand")))
+	       (match_operand:DI 2 "single_bit_mask_operand")))
+   (clobber (match_operand:DI 3 "register_operand"))]
+  "TARGET_64BIT && TARGET_ZBS"
+  [(set (match_dup 3)
+        (match_dup 2))
+   (set (match_dup 0)
+     (any_or:DI (ashift:DI (const_int 1) (match_dup 1))
+		(match_dup 3)))])
+
 (define_insn "*bclr<mode>"
   [(set (match_operand:X 0 "register_operand" "=r")
 	(and:X (rotate:X (const_int -2)
diff --git a/gcc/testsuite/gcc.target/riscv/zbs-zext.c b/gcc/testsuite/gcc.target/riscv/zbs-zext.c
new file mode 100644
index 0000000..5773b15
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zbs-zext.c
@@ -0,0 +1,31 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc_zbs -mabi=lp64" } */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-Og" "-O1" } } */
+typedef unsigned long uint64_t;
+typedef unsigned int uint32_t;
+
+uint64_t bset (const uint32_t i)
+{
+  uint64_t checks = 8;
+  checks |= 1U << i;
+  return checks;
+}
+
+uint64_t binv (const uint32_t i)
+{
+  uint64_t checks = 8;
+  checks ^= 1U << i;
+  return checks;
+}
+
+uint64_t bclr (const uint32_t i)
+{
+  uint64_t checks = 10;
+  checks &= ~(1U << i);
+  return checks;
+}
+
+/* { dg-final { scan-assembler-times "bset\t" 1 } } */
+/* { dg-final { scan-assembler-times "binv\t" 1 } } */
+/* { dg-final { scan-assembler-times "bclr\t" 1 } } */
+/* { dg-final { scan-assembler-not "sllw\t"} } */