Simplify TCG generation of hex_reg_written

Address feedback from Richard Henderson <<richard.henderson@linaro.org>

Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
---
 target/hexagon/genptr.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/target/hexagon/genptr.c b/target/hexagon/genptr.c
index 7481f4c..0ad63fe 100644
--- a/target/hexagon/genptr.c
+++ b/target/hexagon/genptr.c
@@ -43,9 +43,15 @@ static inline void gen_log_predicated_reg_write(int rnum, TCGv val, int slot)
     tcg_gen_movcond_tl(TCG_COND_EQ, hex_new_value[rnum], slot_mask, zero,
                            val, hex_new_value[rnum]);
 #if HEX_DEBUG
-    /* Do this so HELPER(debug_commit_end) will know */
-    tcg_gen_movcond_tl(TCG_COND_EQ, hex_reg_written[rnum], slot_mask, zero,
-                       one, hex_reg_written[rnum]);
+    /*
+     * Do this so HELPER(debug_commit_end) will know
+     *
+     * Note that slot_mask indicates the value is not written
+     * (i.e., slot was cancelled), so we negate the value before
+     * or'ing with hex_reg_written[rnum].
+     */
+    tcg_gen_xori_tl(slot_mask, slot_mask, 1 << slot);
+    tcg_gen_or_tl(hex_reg_written[rnum], hex_reg_written[rnum], slot_mask);
 #endif
 
     tcg_temp_free(one);
-- 
2.7.4

On 3/14/21 10:54 PM, Taylor Simpson wrote:
> Simplify TCG generation of hex_reg_written
> 
> Address feedback from Richard Henderson <<richard.henderson@linaro.org>
> 
> Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
> ---
>   target/hexagon/genptr.c | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/target/hexagon/genptr.c b/target/hexagon/genptr.c
> index 7481f4c..0ad63fe 100644
> --- a/target/hexagon/genptr.c
> +++ b/target/hexagon/genptr.c
> @@ -43,9 +43,15 @@ static inline void gen_log_predicated_reg_write(int rnum, TCGv val, int slot)
>       tcg_gen_movcond_tl(TCG_COND_EQ, hex_new_value[rnum], slot_mask, zero,
>                              val, hex_new_value[rnum]);
>   #if HEX_DEBUG
> -    /* Do this so HELPER(debug_commit_end) will know */
> -    tcg_gen_movcond_tl(TCG_COND_EQ, hex_reg_written[rnum], slot_mask, zero,
> -                       one, hex_reg_written[rnum]);
> +    /*
> +     * Do this so HELPER(debug_commit_end) will know
> +     *
> +     * Note that slot_mask indicates the value is not written
> +     * (i.e., slot was cancelled), so we negate the value before
> +     * or'ing with hex_reg_written[rnum].
> +     */
> +    tcg_gen_xori_tl(slot_mask, slot_mask, 1 << slot);
> +    tcg_gen_or_tl(hex_reg_written[rnum], hex_reg_written[rnum], slot_mask);

reg_written appears to be a boolean, not a mask of any kind.
I think you want

     tcg_gen_setcond_i32(TCG_COND_EQ, slot_mask, slot_mask, zero);

and not the xor.


r~

> -----Original Message-----
> From: Richard Henderson <richard.henderson@linaro.org>
> Sent: Monday, March 15, 2021 8:40 AM
> To: Taylor Simpson <tsimpson@quicinc.com>; qemu-devel@nongnu.org
> Cc: philmd@redhat.com
> Subject: Re: [PATCH] Hexagon (target/hexagon) TCG generation cleanup
>
> On 3/14/21 10:54 PM, Taylor Simpson wrote:
> > Simplify TCG generation of hex_reg_written
> >
> > Address feedback from Richard Henderson
> <<richard.henderson@linaro.org>
> >
> > Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
> > ---
> >   target/hexagon/genptr.c | 12 +++++++++---
> >   1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/target/hexagon/genptr.c b/target/hexagon/genptr.c
> > index 7481f4c..0ad63fe 100644
> > --- a/target/hexagon/genptr.c
> > +++ b/target/hexagon/genptr.c
> > @@ -43,9 +43,15 @@ static inline void gen_log_predicated_reg_write(int
> rnum, TCGv val, int slot)
> >       tcg_gen_movcond_tl(TCG_COND_EQ, hex_new_value[rnum],
> slot_mask, zero,
> >                              val, hex_new_value[rnum]);
> >   #if HEX_DEBUG
> > -    /* Do this so HELPER(debug_commit_end) will know */
> > -    tcg_gen_movcond_tl(TCG_COND_EQ, hex_reg_written[rnum],
> slot_mask, zero,
> > -                       one, hex_reg_written[rnum]);
> > +    /*
> > +     * Do this so HELPER(debug_commit_end) will know
> > +     *
> > +     * Note that slot_mask indicates the value is not written
> > +     * (i.e., slot was cancelled), so we negate the value before
> > +     * or'ing with hex_reg_written[rnum].
> > +     */
> > +    tcg_gen_xori_tl(slot_mask, slot_mask, 1 << slot);
> > +    tcg_gen_or_tl(hex_reg_written[rnum], hex_reg_written[rnum],
> slot_mask);
>
> reg_written appears to be a boolean, not a mask of any kind.
> I think you want
>
>      tcg_gen_setcond_i32(TCG_COND_EQ, slot_mask, slot_mask, zero);
>
> and not the xor.

I'm treating it as a zero/non-zero value.  The change works because the usage in op_helper.c is
    if (env->reg_written[i]) ...

I'll change the xor to setcond to make it more clear.


Thanks,
Taylor