Re: [Qemu-devel] [PATCH 2.3 7/8] tcg: Implement insert_op_before

[Bastian Koppelmann]

On 11/11/2014 04:24 PM, Richard Henderson wrote:

Rather reserving space in the op stream for optimization,
let the optimizer add ops as necessary.

Signed-off-by: Richard Henderson <r...@twiddle.net>
---
  tcg/optimize.c | 57 +++++++++++++++++++++++++++++++++++----------------------
  tcg/tcg-op.c   | 16 ----------------
  2 files changed, 35 insertions(+), 38 deletions(-)

diff --git a/tcg/optimize.c b/tcg/optimize.c
index 973fbb4..067917c 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -67,6 +67,37 @@ static void reset_temp(TCGArg temp)
      temps[temp].mask = -1;
  }

+static TCGOp *insert_op_before(TCGContext *s, TCGOp *old_op,

+                                TCGOpcode opc, int nargs)
+{
+    int oi = s->gen_next_op_idx;
+    int pi = s->gen_next_parm_idx;
+    int prev = old_op->prev;
+    int next = old_op - s->gen_op_buf;
+    TCGOp *new_op;
+
+    tcg_debug_assert(oi < OPC_BUF_SIZE);
+    tcg_debug_assert(pi + nargs <= OPPARAM_BUF_SIZE);

I thinks it is better to assure these assertion always hold, e.g.

    if (oi < OPC_BUF_SIZE || pi + nargs <= OPPARAM_BUF_SIZE) {
        return NULL;
    }
    ...
    TCGOp *op2 = insert_op_before(s, op, INDEX_op_movi_i32, 2);
    if (op2) {
        *args2 = &s->gen_opparam_buf[op2->args];
    }

Or how do we know they always hold?

diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
index fbd82bd..8de259a 100644
--- a/tcg/tcg-op.c
+++ b/tcg/tcg-op.c
@@ -571,8 +571,6 @@ void tcg_gen_add2_i32(TCGv_i32 rl, TCGv_i32 rh, TCGv_i32 al,
  {
      if (TCG_TARGET_HAS_add2_i32) {
          tcg_gen_op6_i32(INDEX_op_add2_i32, rl, rh, al, ah, bl, bh);
-        /* Allow the optimizer room to replace add2 with two moves.  */
-        tcg_gen_op0(&tcg_ctx, INDEX_op_nop);

All references on tcg_gen_op0 are gone, so lets remove it.

Cheers,
Bastian