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>

accel/tcg/plugin-gen.c

@@ -258,12 +258,12 @@ static TCGOp *rm_ops(TCGOp *op)
 
 static TCGOp *copy_op_nocheck(TCGOp **begin_op, TCGOp *op)
 {
-    unsigned nargs = ARRAY_SIZE(op->args);
+    TCGOp *old_op = QTAILQ_NEXT(*begin_op, link);
+    unsigned nargs = old_op->nargs;
 
-    *begin_op = QTAILQ_NEXT(*begin_op, link);
-    tcg_debug_assert(*begin_op);
-    op = tcg_op_insert_after(tcg_ctx, op, (*begin_op)->opc, nargs);
-    memcpy(op->args, (*begin_op)->args, sizeof(op->args));
+    *begin_op = old_op;
+    op = tcg_op_insert_after(tcg_ctx, op, old_op->opc, nargs);
+    memcpy(op->args, old_op->args, sizeof(op->args[0]) * nargs);
 
     return op;
 }

include/exec/helper-head.h

@@ -133,6 +133,4 @@
 #define DEF_HELPER_7(name, ret, t1, t2, t3, t4, t5, t6, t7) \
     DEF_HELPER_FLAGS_7(name, 0, ret, t1, t2, t3, t4, t5, t6, t7)
 
-/* MAX_OPC_PARAM_IARGS must be set to n if last entry is DEF_HELPER_FLAGS_n. */
-
 #endif /* EXEC_HELPER_HEAD_H */

include/tcg/tcg.h

@@ -38,20 +38,6 @@
 /* XXX: make safe guess about sizes */
 #define MAX_OP_PER_INSTR 266
 
-#if HOST_LONG_BITS == 32
-#define MAX_OPC_PARAM_PER_ARG 2
-#else
-#define MAX_OPC_PARAM_PER_ARG 1
-#endif
-#define MAX_OPC_PARAM_IARGS 7
-#define MAX_OPC_PARAM_OARGS 1
-#define MAX_OPC_PARAM_ARGS (MAX_OPC_PARAM_IARGS + MAX_OPC_PARAM_OARGS)
-
-/* 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).  */
-#define MAX_OPC_PARAM (4 + (MAX_OPC_PARAM_PER_ARG * MAX_OPC_PARAM_ARGS))
-
 #define CPU_TEMP_BUF_NLONGS 128
 #define TCG_STATIC_FRAME_SIZE  (CPU_TEMP_BUF_NLONGS * sizeof(long))
 
@@ -493,34 +479,34 @@ typedef struct TCGTempSet {
     unsigned long l[BITS_TO_LONGS(TCG_MAX_TEMPS)];
 } TCGTempSet;
 
-/* While we limit helpers to 6 arguments, for 32-bit hosts, with padding,
-   this imples a max of 6*2 (64-bit in) + 2 (64-bit out) = 14 operands.
-   There are never more than 2 outputs, which means that we can store all
-   dead + sync data within 16 bits.  */
-#define DEAD_ARG  4
-#define SYNC_ARG  1
-typedef uint16_t TCGLifeData;
+/*
+ * With 1 128-bit output, a 32-bit host requires 4 output parameters,
+ * which leaves a maximum of 28 other slots.  Which is enough for 7
+ * 128-bit operands.
+ */
+#define DEAD_ARG  (1 << 4)
+#define SYNC_ARG  (1 << 0)
+typedef uint32_t TCGLifeData;
 
-/* The layout here is designed to avoid a bitfield crossing of
-   a 32-bit boundary, which would cause GCC to add extra padding.  */
 typedef struct TCGOp {
-    TCGOpcode opc   : 8;        /*  8 */
+    TCGOpcode opc   : 8;
+    unsigned nargs  : 8;
 
     /* Parameters for this opcode.  See below.  */
-    unsigned param1 : 4;        /* 12 */
-    unsigned param2 : 4;        /* 16 */
+    unsigned param1 : 8;
+    unsigned param2 : 8;
 
     /* Lifetime data of the operands.  */
-    unsigned life   : 16;       /* 32 */
+    TCGLifeData life;
 
     /* Next and previous opcodes.  */
     QTAILQ_ENTRY(TCGOp) link;
 
-    /* Arguments for the opcode.  */
-    TCGArg args[MAX_OPC_PARAM];
-
     /* Register preferences for the output(s).  */
     TCGRegSet output_pref[2];
+
+    /* Arguments for the opcode.  */
+    TCGArg args[];
 } TCGOp;
 
 #define TCGOP_CALLI(X)    (X)->param1

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;
+    TCGOp *op = NULL;
 
-    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);
+    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;
 }