[gcc(refs/vendors/riscv/heads/gcc-15-with-riscv-opts)] [RISC-V][PR target/120223] Don't use bset/binv for XTHEADBS

[Jeff Law]

https://gcc.gnu.org/g:38d9543602c3acba7276954c306edd487a1528bc

commit 38d9543602c3acba7276954c306edd487a1528bc
Author: Jeff Law <jlaw@ventanamicro.com>
Date:   Thu May 15 09:03:13 2025 -0600

    [RISC-V][PR target/120223] Don't use bset/binv for XTHEADBS
    
    Thead has the XTHEADBB extension which has a lot of overlap with Zbb.  I made
    the incorrect assumption that XTHEADBS would largely be like Zbs when
    generalizing Shreya's work.
    
    As a result we can't use the operation synthesis code for IOR/XOR because we
    don't have binv/bset like capabilities.  I should have double checked on
    XTHEADBS, my bad.
    
    Anyway, the fix is trivial.  Don't allow bset/binv based on XTHEADBS.
    
    Already spun in my tester.  Spinning in the pre-commit CI system now.
    
            PR target/120223
    gcc/
            * config/riscv/riscv.cc (synthesize_ior_xor): XTHEADBS does not have
            single bit manipulations.
    
    gcc/testsuite/
    
            * gcc.target/riscv/pr120223.c: New test.
    
    (cherry picked from commit 87d0daab1ec9d5c901295e8045cbd67f80b2fa23)

Diff:
---
 gcc/config/riscv/riscv.cc                 | 4 ++--
 gcc/testsuite/gcc.target/riscv/pr120223.c | 4 ++++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 295c582072eb..80a725020b1f 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -14245,7 +14245,7 @@ synthesize_ior_xor (rtx_code code, rtx operands[3])
 {
   /* Trivial cases that don't need synthesis.  */
   if (SMALL_OPERAND (INTVAL (operands[2]))
-     || ((TARGET_ZBS || TARGET_XTHEADBS || TARGET_ZBKB)
+     || ((TARGET_ZBS || TARGET_ZBKB)
 	 && single_bit_mask_operand (operands[2], word_mode)))
     return false;
 
@@ -14282,7 +14282,7 @@ synthesize_ior_xor (rtx_code code, rtx operands[3])
   /* If we're flipping all but a small number of bits we can pre-flip
      the outliers, then flip all the bits, which would restore those
      bits that were pre-flipped. */
-  if ((TARGET_ZBS || TARGET_XTHEADBS || TARGET_ZBKB)
+  if ((TARGET_ZBS || TARGET_ZBKB)
       && budget < 0
       && code == XOR
       && popcount_hwi (~INTVAL (operands[2])) < original_budget)
diff --git a/gcc/testsuite/gcc.target/riscv/pr120223.c b/gcc/testsuite/gcc.target/riscv/pr120223.c
new file mode 100644
index 000000000000..fae21b6d1ece
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr120223.c
@@ -0,0 +1,4 @@
+/* { dg-do compile } */
+/* { dg-options "-mcpu=thead-c906" }  */
+long foo(long x) { return x ^ 0x80000000; }
+