[Qemu-devel] [PATCH] target-tilegx: Check zero dest register for ld instructions

[gang.chen.5i5j@gmail.com]

From: Chen Gang <gang.chen.5i5j@gmail.com>

At present, qemu x86_64 host backend can not remove the related dummy
instructions. Even the worse, sometimes, it will generate the incorrect
instructions which will cause segment fault for prefetch_l3 instruction.

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
---
 target-tilegx/translate.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/target-tilegx/translate.c b/target-tilegx/translate.c
index 86da6b5..7232361 100644
--- a/target-tilegx/translate.c
+++ b/target-tilegx/translate.c
@@ -620,7 +620,9 @@ static TileExcp gen_rr_opcode(DisasContext *dc, unsigned opext,
         memop = MO_TEQ;
         mnemonic = "ld";
     do_load:
-        tcg_gen_qemu_ld_tl(tdest, tsrca, dc->mmuidx, memop);
+        if (dest != TILEGX_R_ZERO) {
+            tcg_gen_qemu_ld_tl(tdest, tsrca, dc->mmuidx, memop);
+        }
         break;
     case OE_RR_X1(LDNA):
         tcg_gen_andi_tl(tdest, tsrca, ~7);
@@ -1987,8 +1989,10 @@ static TileExcp decode_y2(DisasContext *dc, tilegx_bundle_bits bundle)
         memop = MO_TEQ;
         mnemonic = "ld";
     do_load:
-        tcg_gen_qemu_ld_tl(dest_gr(dc, srcbdest), load_gr(dc, srca),
-                           dc->mmuidx, memop);
+        if (srcbdest != TILEGX_R_ZERO) {
+            tcg_gen_qemu_ld_tl(dest_gr(dc, srcbdest), load_gr(dc, srca),
+                               dc->mmuidx, memop);
+        }
         qemu_log_mask(CPU_LOG_TB_IN_ASM, "%s %s, %s", mnemonic,
                       reg_names[srcbdest], reg_names[srca]);
         return TILEGX_EXCP_NONE;
-- 
1.9.3