[Qemu-devel] [PATCH] tcg/mips: reserve a register for the guest_base.

[Qemu-devel] [PATCH] tcg/mips: reserve a register for the guest_base.

[Jiang Biao]

Reserve a register for the guest_base using ppc code for reference.
By doing so, we do not have to recompute it for every memory load.

Signed-off-by: Jiang Biao <jiang.biao2@zte.com.cn>
Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 tcg/mips/tcg-target.inc.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/tcg/mips/tcg-target.inc.c b/tcg/mips/tcg-target.inc.c
index 85756b8..1a8169f 100644
--- a/tcg/mips/tcg-target.inc.c
+++ b/tcg/mips/tcg-target.inc.c
@@ -85,6 +85,10 @@ static const char * const tcg_target_reg_names[TCG_TARGET_NB_REGS] = {
 #define TCG_TMP2  TCG_REG_T8
 #define TCG_TMP3  TCG_REG_T7
 
+#ifndef CONFIG_SOFTMMU
+#define TCG_GUEST_BASE_REG TCG_REG_S1
+#endif
+
 /* check if we really need so many registers :P */
 static const int tcg_target_reg_alloc_order[] = {
     /* Call saved registers.  */
@@ -1547,8 +1551,7 @@ static void tcg_out_qemu_ld(TCGContext *s, const TCGArg *args, bool is_64)
     } else if (guest_base == (int16_t)guest_base) {
         tcg_out_opc_imm(s, ALIAS_PADDI, base, addr_regl, guest_base);
     } else {
-        tcg_out_movi(s, TCG_TYPE_PTR, TCG_TMP0, guest_base);
-        tcg_out_opc_reg(s, ALIAS_PADD, base, TCG_TMP0, addr_regl);
+        tcg_out_opc_reg(s, ALIAS_PADD, base, TCG_GUEST_BASE_REG, addr_regl);
     }
     tcg_out_qemu_ld_direct(s, data_regl, data_regh, base, opc, is_64);
 #endif
@@ -1652,8 +1655,7 @@ static void tcg_out_qemu_st(TCGContext *s, const TCGArg *args, bool is_64)
     } else if (guest_base == (int16_t)guest_base) {
         tcg_out_opc_imm(s, ALIAS_PADDI, base, addr_regl, guest_base);
     } else {
-        tcg_out_movi(s, TCG_TYPE_PTR, TCG_TMP0, guest_base);
-        tcg_out_opc_reg(s, ALIAS_PADD, base, TCG_TMP0, addr_regl);
+        tcg_out_opc_reg(s, ALIAS_PADD, base, TCG_GUEST_BASE_REG, addr_regl);
     }
     tcg_out_qemu_st_direct(s, data_regl, data_regh, base, opc);
 #endif
@@ -2452,6 +2454,13 @@ static void tcg_target_qemu_prologue(TCGContext *s)
                    TCG_REG_SP, SAVE_OFS + i * REG_SIZE);
     }
 
+#ifndef CONFIG_SOFTMMU
+    if (guest_base) {
+        tcg_out_movi(s, TCG_TYPE_PTR, TCG_GUEST_BASE_REG, guest_base);
+        tcg_regset_set_reg(s->reserved_regs, TCG_GUEST_BASE_REG);
+    }
+#endif
+
     /* Call generated code */
     tcg_out_opc_reg(s, OPC_JR, 0, tcg_target_call_iarg_regs[1], 0);
     /* delay slot */
-- 
2.7.4

Re: [Qemu-devel] [PATCH] tcg/mips: reserve a register for the guest_base.

[Richard Henderson]

On 07/09/2017 11:12 PM, Jiang Biao wrote:
> Reserve a register for the guest_base using ppc code for reference.
> By doing so, we do not have to recompute it for every memory load.
> 
> Signed-off-by: Jiang Biao<jiang.biao2@zte.com.cn>
> Signed-off-by: Richard Henderson<rth@twiddle.net>
> ---
>   tcg/mips/tcg-target.inc.c | 17 +++++++++++++----
>   1 file changed, 13 insertions(+), 4 deletions(-)

For future reference, you should not add a Signed-off-by for someone else. 
That is like writing someone else's signature.

You may acknowledge my suggestion with a Suggested-by tag.

QEMU uses the same rules for this as does the linux kernel.  Please read

> https://github.com/torvalds/linux/blob/master/Documentation/process/submitting-patches.rst

or at least section 11 from

> https://github.com/torvalds/linux/blob/master/Documentation/translations/zh_CN/SubmittingPatches

(The translation may be be out of date.  I don't see any of the other tags, 
like Suggested-by, within the Chinese text.)

That said, applied to tcg-next.


r~