[PATCH v3 4/8] mips: Fill delay slots of J in jit_jmpi

[Paul Cercueil]

When we know that the last generated opcode is not the target of a jump,
we can swap it with the J opcode, so that it now becomes the delay slot
of the J opcode.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---
 lib/jit_mips-cpu.c | 46 ++++++++++++++++++++++++++++++++++++----------
 lib/jit_mips.c     |  6 +++---
 2 files changed, 39 insertions(+), 13 deletions(-)

diff --git a/lib/jit_mips-cpu.c b/lib/jit_mips-cpu.c
index 028b806..d2852f2 100644
--- a/lib/jit_mips-cpu.c
+++ b/lib/jit_mips-cpu.c
@@ -715,8 +715,8 @@ static jit_word_t 
_bner(jit_state_t*,jit_word_t,jit_int32_t,jit_int32_t);
 static jit_word_t _bnei(jit_state_t*,jit_word_t,jit_int32_t,jit_word_t);
 #  define jmpr(r0,prev)                        _jmpr(_jit,r0,prev)
 static void _jmpr(jit_state_t*,jit_int32_t,jit_node_t*);
-#  define jmpi(i0)                     _jmpi(_jit,i0)
-static jit_word_t _jmpi(jit_state_t*,jit_word_t);
+#  define jmpi(i0,prev)                        _jmpi(_jit,i0,prev)
+static jit_word_t _jmpi(jit_state_t*,jit_word_t,jit_node_t*);
 #  define boaddr(i0,r0,r1)             _boaddr(_jit,i0,r0,r1)
 static jit_word_t _boaddr(jit_state_t*,jit_word_t,jit_int32_t,jit_int32_t);
 #  define boaddi(i0,r0,i1)             _boaddi(_jit,i0,r0,i1)
@@ -2646,21 +2646,47 @@ _jmpr(jit_state_t *_jit, jit_int32_t r0, jit_node_t 
*prev)
 }
 
 static jit_word_t
-_jmpi(jit_state_t *_jit, jit_word_t i0)
+_jmpi(jit_state_t *_jit, jit_word_t i0, jit_node_t *prev)
 {
     jit_word_t         w;
-    jit_int32_t                reg;
+    jit_int32_t                reg, op, offset;
+    jit_bool_t         swap_ds;
+
+    swap_ds = can_swap_ds(prev, 0, 0);
 
     w = _jit->pc.w;
     if (((w + sizeof(jit_int32_t)) & 0xf0000000) == (i0 & 0xf0000000)) {
-       J((i0 & ~0xf0000000) >> 2);
-       NOP(1);
+        if (swap_ds) {
+            op = *--_jit->pc.ui;
+            w -= sizeof(jit_int32_t);
+        }
+
+        J((i0 & ~0xf0000000) >> 2);
+        if (swap_ds)
+            ii(op);
+        else
+            NOP(1);
     }
     else {
-       reg = jit_get_reg(jit_class_gpr|jit_class_nospill);
-       movi_p(rn(reg), i0);
-       jmpr(rn(reg), NULL);
-       jit_unget_reg(reg);
+        reg = get_reg_can_swap(swap_ds);
+        if (reg == JIT_NOREG) {
+            swap_ds = 0;
+            reg = jit_get_reg(jit_class_gpr|jit_class_nospill);
+        }
+
+        if (swap_ds)
+            op = *--_jit->pc.ui;
+
+        movi_p(rn(reg), i0);
+
+        w = _jit->pc.w;
+        JR(rn(reg));
+        if (swap_ds)
+            ii(op);
+        else
+            NOP(1);
+
+        jit_unget_reg(reg);
     }
 
     return (w);
diff --git a/lib/jit_mips.c b/lib/jit_mips.c
index a6afec9..6694b5a 100644
--- a/lib/jit_mips.c
+++ b/lib/jit_mips.c
@@ -1695,14 +1695,14 @@ _emit_code(jit_state_t *_jit)
                    assert(temp->code == jit_code_label ||
                           temp->code == jit_code_epilog);
                    if (temp->flag & jit_flag_patch)
-                       jmpi(temp->u.w);
+                       jmpi(temp->u.w, prev);
                    else {
-                       word = jmpi(_jit->pc.w);
+                       word = jmpi(_jit->pc.w, prev);
                        patch(word, node);
                    }
                }
                else
-                   jmpi(node->u.w);
+                   jmpi(node->u.w, prev);
                break;
            case jit_code_callr:
                callr(rn(node->u.w), prev);
-- 
2.39.0