tcg: Vary the allocation size for TCGOp

We have been allocating a worst case number of arguments
to support calls.  Instead, allow the size to vary.
By default leave space for 4 args, to maximize reuse,
but allow calls to increase the number of args to 32.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
[PMD: Split patch in two]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20221218211832.73312-3-philmd@linaro.org>

1 files changed, 27 insertions, 10 deletions

diff --git a/tcg/tcg.c b/tcg/tcg.c
index ecbbe99..be55e14 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -1513,7 +1513,12 @@ void tcg_gen_callN(void *func, TCGTemp *ret, int nargs, TCGTemp **args)
         }
     }
 
-    max_args = ARRAY_SIZE(op->args);
+    /*
+     * A Call op needs up to 4 + 2N parameters on 32-bit archs,
+     * and up to 4 + N parameters on 64-bit archs
+     * (N = number of input arguments + output arguments).
+     */
+    max_args = (64 / TCG_TARGET_REG_BITS) * nargs + 4;
     op = tcg_emit_op(INDEX_op_call, max_args);
 
     pi = 0;
@@ -2298,19 +2303,31 @@ void tcg_remove_ops_after(TCGOp *op)
 static TCGOp *tcg_op_alloc(TCGOpcode opc, unsigned nargs)
 {
     TCGContext *s = tcg_ctx;
-    TCGOp *op;
-
-    assert(nargs < ARRAY_SIZE(op->args));
-    if (likely(QTAILQ_EMPTY(&s->free_ops))) {
-        op = tcg_malloc(sizeof(TCGOp));
-    } else {
-        op = QTAILQ_FIRST(&s->free_ops);
-        QTAILQ_REMOVE(&s->free_ops, op, link);
+    TCGOp *op = NULL;
+
+    if (unlikely(!QTAILQ_EMPTY(&s->free_ops))) {
+        QTAILQ_FOREACH(op, &s->free_ops, link) {
+            if (nargs <= op->nargs) {
+                QTAILQ_REMOVE(&s->free_ops, op, link);
+                nargs = op->nargs;
+                goto found;
+            }
+        }
     }
+
+    /* Most opcodes have 3 or 4 operands: reduce fragmentation. */
+    nargs = MAX(4, nargs);
+    op = tcg_malloc(sizeof(TCGOp) + sizeof(TCGArg) * nargs);
+
+ found:
     memset(op, 0, offsetof(TCGOp, link));
     op->opc = opc;
-    s->nb_ops++;
+    op->nargs = nargs;
+
+    /* Check for bitfield overflow. */
+    tcg_debug_assert(op->nargs == nargs);
 
+    s->nb_ops++;
     return op;
 }