diff mbox series

[v4,09/10] RISCV: Weaken atomic loads

Message ID 20230414170942.1695672-10-patrick@rivosinc.com
State Accepted
Headers
Series RISCV: Implement ISA Manual Table A.6 Mappings |

Checks

Context Check Description
snail/gcc-patch-check success Github commit url

Commit Message

Patrick O'Neill April 14, 2023, 5:09 p.m. UTC 
  This change brings atomic loads in line with table A.6 of the ISA
manual.

2023-04-14 Patrick O'Neill <patrick@rivosinc.com>

	* sync.md (atomic_load<mode>): Implement atomic load mapping.

Signed-off-by: Patrick O'Neill <patrick@rivosinc.com>
---
v3 Changelog:
* Add this patch
---
 gcc/config/riscv/sync.md | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/gcc/config/riscv/sync.md b/gcc/config/riscv/sync.md
index e91fa29da51..9e3685f5b1c 100644
--- a/gcc/config/riscv/sync.md
+++ b/gcc/config/riscv/sync.md
@@ -23,6 +23,7 @@ 
   UNSPEC_COMPARE_AND_SWAP
   UNSPEC_SYNC_OLD_OP
   UNSPEC_SYNC_EXCHANGE
+  UNSPEC_ATOMIC_LOAD
   UNSPEC_ATOMIC_STORE
   UNSPEC_MEMORY_BARRIER
 ])
@@ -63,7 +64,31 @@ 
 
 ;; Atomic memory operations.
 
-;; Implement atomic stores with conservative fences. Fall back to fences for atomic loads.
+(define_insn "atomic_load<mode>"
+  [(set (match_operand:GPR 0 "register_operand" "=r")
+    (unspec_volatile:GPR
+      [(match_operand:GPR 1 "memory_operand" "A")
+       (match_operand:SI 2 "const_int_operand")]      ;; model
+      UNSPEC_ATOMIC_LOAD))]
+  "TARGET_ATOMIC"
+  {
+    enum memmodel model = (enum memmodel) INTVAL (operands[2]);
+    model = memmodel_base (model);
+
+    if (model == MEMMODEL_SEQ_CST)
+      return "fence\trw,rw\;"
+	     "l<amo>\t%0,%1\;"
+	     "fence\tr,rw";
+    if (model == MEMMODEL_ACQUIRE)
+      return "l<amo>\t%0,%1\;"
+	     "fence\tr,rw";
+    else
+      return "l<amo>\t%0,%1";
+  }
+  [(set_attr "type" "atomic")
+   (set (attr "length") (const_int 12))])
+
+;; Implement atomic stores with conservative fences.
 ;; This allows us to be compatible with the ISA manual Table A.6 and Table A.7.
 (define_insn "atomic_store<mode>"
   [(set (match_operand:GPR 0 "memory_operand" "=A")