[gcc r14-233] avoid splitting small constants in bcrli_nottwobits patterns

[gcc r14-233] avoid splitting small constants in bcrli_nottwobits patterns

[Jeff Law]

https://gcc.gnu.org/g:392200f807fe2ee377ecc451ff75894b89335c33

commit r14-233-g392200f807fe2ee377ecc451ff75894b89335c33
Author: Jivan Hakobyan <jivanhakobyan9@gmail.com>
Date:   Tue Apr 25 20:41:02 2023 -0600

    avoid splitting small constants in bcrli_nottwobits patterns
    
    I have noticed that in the case when we try to clear two bits through a
    small constant,
    and ZBS is enabled then GCC split it into two "andi" instructions.
    For example for the following C code:
      int foo(int a) {
        return a & ~ 0x101;
      }
    
    GCC generates the following:
      foo:
         andi a0,a0,-2
         andi a0,a0,-257
         ret
    
    but should be this one:
      foo:
         andi a0,a0,-258
         ret
    
    This patch solves the mentioned issue.
    
    gcc/ChangeLog
            * config/riscv/bitmanip.md: Updated predicates of bclri<mode>_nottwobits
            and bclridisi_nottwobits patterns.
            * config/riscv/predicates.md: (not_uimm_extra_bit_or_nottwobits): Adjust
            predicate to avoid splitting arith constants.
            (const_nottwobits_not_arith_operand): New predicate.
    
    gcc/testsuite
            * gcc.target/riscv/zbs-bclri-nottwobits.c: New test.

Diff:
---
 gcc/config/riscv/bitmanip.md                          |  4 ++--
 gcc/config/riscv/predicates.md                        |  7 ++++++-
 gcc/testsuite/gcc.target/riscv/zbs-bclri-nottwobits.c | 14 ++++++++++++++
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/gcc/config/riscv/bitmanip.md b/gcc/config/riscv/bitmanip.md
index 44ad350c747..c21247aa3fa 100644
--- a/gcc/config/riscv/bitmanip.md
+++ b/gcc/config/riscv/bitmanip.md
@@ -508,7 +508,7 @@
 (define_insn_and_split "*bclri<mode>_nottwobits"
   [(set (match_operand:X 0 "register_operand" "=r")
 	(and:X (match_operand:X 1 "register_operand" "r")
-	       (match_operand:X 2 "const_nottwobits_operand" "i")))]
+	       (match_operand:X 2 "const_nottwobits_not_arith_operand" "i")))]
   "TARGET_ZBS && !paradoxical_subreg_p (operands[1])"
   "#"
   "&& reload_completed"
@@ -527,7 +527,7 @@
 (define_insn_and_split "*bclridisi_nottwobits"
   [(set (match_operand:DI 0 "register_operand" "=r")
 	(and:DI (match_operand:DI 1 "register_operand" "r")
-		(match_operand:DI 2 "const_nottwobits_operand" "i")))]
+		(match_operand:DI 2 "const_nottwobits_not_arith_operand" "i")))]
   "TARGET_64BIT && TARGET_ZBS
    && clz_hwi (~UINTVAL (operands[2])) > 33"
   "#"
diff --git a/gcc/config/riscv/predicates.md b/gcc/config/riscv/predicates.md
index 8654dbc5943..e5adf06fa25 100644
--- a/gcc/config/riscv/predicates.md
+++ b/gcc/config/riscv/predicates.md
@@ -366,6 +366,11 @@
   (and (match_code "const_int")
        (match_test "popcount_hwi (~UINTVAL (op)) == 2")))
 
+(define_predicate "const_nottwobits_not_arith_operand"
+  (and (match_code "const_int")
+       (and (not (match_operand 0 "arith_operand"))
+	    (match_operand 0 "const_nottwobits_operand"))))
+
 ;; A CONST_INT operand that consists of a single run of 32 consecutive
 ;; set bits.
 (define_predicate "consecutive_bits32_operand"
@@ -411,4 +416,4 @@
 (define_predicate "not_uimm_extra_bit_or_nottwobits"
   (and (match_code "const_int")
        (ior (match_operand 0 "not_uimm_extra_bit_operand")
-	    (match_operand 0 "const_nottwobits_operand"))))
+	    (match_operand 0 "const_nottwobits_not_arith_operand"))))
diff --git a/gcc/testsuite/gcc.target/riscv/zbs-bclri-nottwobits.c b/gcc/testsuite/gcc.target/riscv/zbs-bclri-nottwobits.c
new file mode 100644
index 00000000000..5a58e0a1185
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zbs-bclri-nottwobits.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc_zbs -mabi=lp64" } */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-Og" } } */
+
+int and_two_bit(int idx) {
+    return idx & ~3;
+}
+
+int and_bclr_two_bit(int idx) {
+    return idx & ~(0x4001);
+}
+
+/* { dg-final { scan-assembler-times "\tandi\t" 2 } } */
+/* { dg-final { scan-assembler-times "\tbclri\t" 1 } } */