[PATCH v2 3/8] RISCV: Enforce atomic compare_exchange SEQ_CST

[Patrick O'Neill]

This patch enforces SEQ_CST for atomic compare_exchange ops.

Replace Fence/LR.aq/SC.aq pairs with strong SEQ_CST LR.aqrl/SC.rl pairs
recommended by table A.6 of the ISA manual.

2023-04-05 Patrick O'Neill <patr...@rivosinc.com>

        * sync.md: Change FENCE/LR.aq/SC.aq into sequentially
        consistent LR.aqrl/SC.rl pair.

Signed-off-by: Patrick O'Neill <patr...@rivosinc.com>
---
 gcc/config/riscv/sync.md | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/gcc/config/riscv/sync.md b/gcc/config/riscv/sync.md
index c932ef87b9d..de42245981b 100644
--- a/gcc/config/riscv/sync.md
+++ b/gcc/config/riscv/sync.md
@@ -115,9 +115,16 @@
         UNSPEC_COMPARE_AND_SWAP))
    (clobber (match_scratch:GPR 6 "=&r"))]
   "TARGET_ATOMIC"
-  "%F5 1: lr.<amo>%A5 %0,%1; bne %0,%z2,1f; sc.<amo>%A4 %6,%z3,%1; bnez %6,1b; 
1:"
+  {
+    return "1:\;"
+          "lr.<amo>.aqrl\t%0,%1\;"
+          "bne\t%0,%z2,1f\;"
+          "sc.<amo>.rl\t%6,%z3,%1\;"
+          "bnez\t%6,1b\;"
+          "1:";
+  }
   [(set_attr "type" "atomic")
-   (set (attr "length") (const_int 20))])
+   (set (attr "length") (const_int 16))])
 
 (define_expand "atomic_compare_and_swap<mode>"
   [(match_operand:SI 0 "register_operand" "")   ;; bool output
-- 
2.25.1