[1/4] target-arm: Remove redundant setting of IT bits before Thumb SWI

Submitted by Peter Maydell on Jan. 10, 2011, 11:11 p.m.

Details

Message ID 1294701112-14071-2-git-send-email-peter.maydell@linaro.org
State New
Headers show

Commit Message

Peter Maydell Jan. 10, 2011, 11:11 p.m.
Remove a redundant call to gen_set_condexec() in the translation of Thumb
mode SWI. (SWI and WFI generate "exceptions" which happen after the
execution of the instruction, ie when PC and IT bits have updated.
So the condexec bits at this point are not correct. However, the code
that handles finishing the translation of the TB will write the correct
value of the condexec bits later, so the only effect was that a conditional
Thumb SWI would generate slightly worse code than necessary.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target-arm/translate.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

Comments

Aurelien Jarno Jan. 11, 2011, 11:06 p.m.
On Mon, Jan 10, 2011 at 11:11:49PM +0000, Peter Maydell wrote:
> Remove a redundant call to gen_set_condexec() in the translation of Thumb
> mode SWI. (SWI and WFI generate "exceptions" which happen after the
> execution of the instruction, ie when PC and IT bits have updated.
> So the condexec bits at this point are not correct. However, the code
> that handles finishing the translation of the TB will write the correct
> value of the condexec bits later, so the only effect was that a conditional
> Thumb SWI would generate slightly worse code than necessary.)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target-arm/translate.c |    1 -
>  1 files changed, 0 insertions(+), 1 deletions(-)

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>

> diff --git a/target-arm/translate.c b/target-arm/translate.c
> index 2ce82f3..4abece1 100644
> --- a/target-arm/translate.c
> +++ b/target-arm/translate.c
> @@ -9014,7 +9014,6 @@ static void disas_thumb_insn(CPUState *env, DisasContext *s)
>  
>          if (cond == 0xf) {
>              /* swi */
> -            gen_set_condexec(s);
>              gen_set_pc_im(s->pc);
>              s->is_jmp = DISAS_SWI;
>              break;
> -- 
> 1.7.1
> 
> 
>

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diff --git a/target-arm/translate.c b/target-arm/translate.c
index 2ce82f3..4abece1 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -9014,7 +9014,6 @@  static void disas_thumb_insn(CPUState *env, DisasContext *s)
 
         if (cond == 0xf) {
             /* swi */
-            gen_set_condexec(s);
             gen_set_pc_im(s->pc);
             s->is_jmp = DISAS_SWI;
             break;