[PATCH v2 5/8] RISC-V: Recognize bexti in negated if-conversion

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

While the positive case "if ((bits >> SHAMT) & 1)" for SHAMT 0..10 can
trigger conversion into efficient branchless sequences
  - with Zbs (bexti + neg + and)
  - with XVentanaCondOps (andi + vt.maskc)
the inverted/negated case results in
  andi a5,a0,1024
  seqz a5,a5
  neg a5,a5
  and a5,a5,a1
due to how the sequence presents to the combine pass.

This adds an additional splitter to reassociate the polarity reversed
case into bexti + addi, if Zbs is present.

gcc/ChangeLog:

    * config/riscv/xventanacondops.md: Add split to reassociate
      "andi + seqz + neg" into "bexti + addi".

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

Changes in v2:
- Removed spurious empty line at the end of xventanacondops.md.

 gcc/config/riscv/xventanacondops.md | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/gcc/config/riscv/xventanacondops.md b/gcc/config/riscv/xventanacondops.md
index a4068e53c13..81e5e8a8298 100644
--- a/gcc/config/riscv/xventanacondops.md
+++ b/gcc/config/riscv/xventanacondops.md
@@ -119,3 +119,13 @@
 {
   operands[2] = GEN_INT(1 << UINTVAL(operands[2]));
 })
+
+(define_split
+  [(set (match_operand:X 0 "register_operand")
+	(neg:X (eq:X (zero_extract:X (match_operand:X 1 "register_operand")
+				     (const_int 1)
+				     (match_operand 2 "immediate_operand"))
+		     (const_int 0))))]
+  "!TARGET_XVENTANACONDOPS && TARGET_ZBS"
+  [(set (match_dup 0) (zero_extract:X (match_dup 1) (const_int 1) (match_dup 2)))
+   (set (match_dup 0) (plus:X (match_dup 0) (const_int -1)))])
-- 
2.34.1