[Qemu-devel] [RFC][PATCH v0 3/8] Do better spill choice.

[Kirill Batuzov]

Choose register with farthest next use for spilling.

Signed-off-by: Kirill Batuzov <batuz...@ispras.ru>
---
 tcg/tcg.c |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/tcg/tcg.c b/tcg/tcg.c
index c6e920e..61689e2 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -1528,6 +1528,9 @@ static void tcg_reg_free(TCGContext *s, int reg)
 static int tcg_reg_alloc(TCGContext *s, TCGRegSet reg1, TCGRegSet reg2)
 {
     int i, reg;
+#ifdef USE_ADVANCED_REGALLOC
+    int best_reg = -1, best_score = -2;
+#endif
     TCGRegSet reg_ct;
 
     tcg_regset_andnot(reg_ct, reg1, reg2);
@@ -1543,11 +1546,29 @@ static int tcg_reg_alloc(TCGContext *s, TCGRegSet reg1, 
TCGRegSet reg2)
     for(i = 0; i < ARRAY_SIZE(tcg_target_reg_alloc_order); i++) {
         reg = tcg_target_reg_alloc_order[i];
         if (tcg_regset_test_reg(reg_ct, reg)) {
+#ifdef USE_ADVANCED_REGALLOC
+            if (s->reg_next_use[reg] > best_score ||
+                s->reg_next_use[reg] == -1) {
+                best_reg = reg;
+                best_score = s->reg_next_use[reg];
+                if (best_score == -1) {
+                    best_score = OPPARAM_BUF_SIZE + 1;
+                }
+            }
+#else
             tcg_reg_free(s, reg);
             return reg;
+#endif
         }
     }
 
+#ifdef USE_ADVANCED_REGALLOC
+    if (best_score >= 0 && best_reg >= 0) {
+        tcg_reg_free(s, best_reg);
+        return best_reg;
+    }
+#endif
+
     tcg_abort();
 }
 
-- 
1.7.4.1