* [PATCH] target/mips: Simplify Loongson MULTU.G opcode
@ 2023-08-31 20:11 Philippe Mathieu-Daudé
2023-08-31 23:26 ` Richard Henderson
0 siblings, 1 reply; 2+ messages in thread
From: Philippe Mathieu-Daudé @ 2023-08-31 20:11 UTC (permalink / raw)
To: qemu-devel
Cc: Aurelien Jarno, Aleksandar Rikalo, Jiaxun Yang,
Philippe Mathieu-Daudé, Richard Henderson
Since MULTU opcodes don't record the most significant bits
of the infinite result, sign-extending the sources make no
difference in the result.
Once we remove the sign extension of source registers, MULT
and MULTU are identical (as are DMULT and DMULTU).
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
target/mips/tcg/translate.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/target/mips/tcg/translate.c b/target/mips/tcg/translate.c
index 9bb40f1849..e0a76b9432 100644
--- a/target/mips/tcg/translate.c
+++ b/target/mips/tcg/translate.c
@@ -3625,8 +3625,6 @@ static void gen_loongson_integer(DisasContext *ctx, uint32_t opc,
break;
case OPC_MULTU_G_2E:
case OPC_MULTU_G_2F:
- tcg_gen_ext32u_tl(t0, t0);
- tcg_gen_ext32u_tl(t1, t1);
tcg_gen_mul_tl(cpu_gpr[rd], t0, t1);
tcg_gen_ext32s_tl(cpu_gpr[rd], cpu_gpr[rd]);
break;
--
2.41.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] target/mips: Simplify Loongson MULTU.G opcode
2023-08-31 20:11 [PATCH] target/mips: Simplify Loongson MULTU.G opcode Philippe Mathieu-Daudé
@ 2023-08-31 23:26 ` Richard Henderson
0 siblings, 0 replies; 2+ messages in thread
From: Richard Henderson @ 2023-08-31 23:26 UTC (permalink / raw)
To: Philippe Mathieu-Daudé, qemu-devel
Cc: Aurelien Jarno, Aleksandar Rikalo, Jiaxun Yang
On 8/31/23 13:11, Philippe Mathieu-Daudé wrote:
> Since MULTU opcodes don't record the most significant bits
> of the infinite result, sign-extending the sources make no
> difference in the result.
>
> Once we remove the sign extension of source registers, MULT
> and MULTU are identical (as are DMULT and DMULTU).
>
> Suggested-by: Richard Henderson<richard.henderson@linaro.org>
> Signed-off-by: Philippe Mathieu-Daudé<philmd@linaro.org>
> ---
> target/mips/tcg/translate.c | 2 --
> 1 file changed, 2 deletions(-)
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
r~
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