Re: [patch] Disable if_conversion2 for Og
On Tue, Apr 15, 2014 at 3:59 AM, Joey Ye wrote:
> If-converstion is harmful to optimized debugging as it generates conditional
> execution instructions with line number information, which resulted in a
> dillusion to developers that both then-else branches are executed.
>
> For example:
> test.c:
> 1: unsigned oldest_sequence;
> 2:
> 3: unsigned foo(unsigned seq_number)
> 4: {
> 5: if ((seq_number + 5) < 10)
> 6:seq_number += 100;
> 7: else
> 8: seq_number = oldest_sequence;
>
> if (seq_number < oldest_sequence)
> seq_number = oldest_sequence;
>
> return seq_number;
> }
>
> $ arm-none-eabi-gcc -mthumb -mcpu=cortex-m3 -Og -g3
> gets:
> .loc 1 5 0
> addsr3, r0, #5
> cmp r3, #9
> .loc 1 6 0 <- line 6, then branch
> iteels
> addls r0, r0, #100
> .LVL1:
> .loc 1 8 0 <- line 8, else branch. Both branches seems to
> be executed in GDB
> ldrhi r3, .L5
> ldrhi r0, [r3]
>
> The reason is that if_conversion2 is still enabled in Og. The patch simply
> disables it for Og.
>
> Tests:
> * -Og bootstrap passed.
> * Make check default (no additional option): No regression.
> * Make check with -Og: expected regressions. Cases relying on if-conversion2
> failed.
>> FAIL: gcc.target/arm/its.c scan-assembler-times \\tit 2
>> FAIL: gcc.target/arm/pr40956.c scan-assembler-times mov[t ]*r., #0 1
>> FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler asreq
>> FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler lslne
>> FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler asrne
>> FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler lslne
>
> OK to trunk and 4.8/4.9 branch?
Ok for trunk and branches after a while. Why does if-conversion not have
the same problem? On the GIMPLE part we avoid all kinds of if-conversion
with -Og.
Thanks,
Richard.
> ChangeLog:
> * opts.c (OPT_fif_conversion2): Disable for Og.
>
> diff --git a/gcc/opts.c b/gcc/opts.c
> index fdc903f..e076253 100644
> --- a/gcc/opts.c
> +++ b/gcc/opts.c
> @@ -432,7 +432,7 @@ static const struct default_options
> default_options_table[] =
> { OPT_LEVELS_1_PLUS, OPT_fcprop_registers, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fforward_propagate, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fif_conversion, NULL, 1 },
> -{ OPT_LEVELS_1_PLUS, OPT_fif_conversion2, NULL, 1 },
> +{ OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fif_conversion2, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fipa_pure_const, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fipa_reference, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fipa_profile, NULL, 1 },
>
>
RE: [patch] Disable if_conversion2 for Og
> -Original Message-
> From: Richard Biener [mailto:richard.guent...@gmail.com]
> Sent: Tuesday, April 15, 2014 4:05 PM
> To: Joey Ye
> Cc: GCC Patches
> Subject: Re: [patch] Disable if_conversion2 for Og
>
> On Tue, Apr 15, 2014 at 3:59 AM, Joey Ye wrote:
> > If-converstion is harmful to optimized debugging as it generates
> > conditional execution instructions with line number information, which
> > resulted in a dillusion to developers that both then-else branches are
> executed.
> >
> > For example:
> > test.c:
> > 1: unsigned oldest_sequence;
> > 2:
> > 3: unsigned foo(unsigned seq_number)
> > 4: {
> > 5: if ((seq_number + 5) < 10)
> > 6:seq_number += 100;
> > 7: else
> > 8: seq_number = oldest_sequence;
> >
> > if (seq_number < oldest_sequence)
> > seq_number = oldest_sequence;
> >
> > return seq_number;
> > }
> >
> > $ arm-none-eabi-gcc -mthumb -mcpu=cortex-m3 -Og -g3
> > gets:
> > .loc 1 5 0
> > addsr3, r0, #5
> > cmp r3, #9
> > .loc 1 6 0 <- line 6, then branch
> > iteels
> > addls r0, r0, #100
> > .LVL1:
> > .loc 1 8 0 <- line 8, else branch. Both branches seems to
> > be executed in GDB
> > ldrhi r3, .L5
> > ldrhi r0, [r3]
> >
> > The reason is that if_conversion2 is still enabled in Og. The patch
> > simply disables it for Og.
> >
> > Tests:
> > * -Og bootstrap passed.
> > * Make check default (no additional option): No regression.
> > * Make check with -Og: expected regressions. Cases relying on
> > if-conversion2 failed.
> >> FAIL: gcc.target/arm/its.c scan-assembler-times \\tit 2
> >> FAIL: gcc.target/arm/pr40956.c scan-assembler-times mov[t ]*r.,
> >> #0 1
> >> FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler asreq
> >> FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler lslne
> >> FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler asrne
> >> FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler lslne
> >
> > OK to trunk and 4.8/4.9 branch?
>
> Ok for trunk and branches after a while. Why does if-conversion not have
> the same problem? On the GIMPLE part we avoid all kinds of if-conversion
> with -Og.
I think if-conversion should be disabled for Og too, but I don't have a case to
show that it is harmful. If GIMPLE avoids all if-conversion, it is nature to do
the same for RTL. I'll test and send another patch to also disable
if-conversion.
RE: [patch] Disable if_conversion2 for Og
> -Original Message-
> From: Joey Ye [mailto:joey...@arm.com]
> Sent: Tuesday, April 15, 2014 6:37 PM
> To: 'Richard Biener'
> Cc: GCC Patches
> Subject: RE: [patch] Disable if_conversion2 for Og
>
> > Ok for trunk and branches after a while. Why does if-conversion not have
> > the same problem? On the GIMPLE part we avoid all kinds of if-conversion
> > with -Og.
> I think if-conversion should be disabled for Og too, but I don't have a case
> to
> show that it is harmful. If GIMPLE avoids all if-conversion, it is nature to
> do
> the same for RTL. I'll test and send another patch to also disable
> if-conversion.
New patch tested with more regressions with -Og, which are expected.
FAIL: gcc.target/arm/its.c scan-assembler-times \\tit 2
FAIL: gcc.target/arm/pr40956.c scan-assembler-times mov[t ]*r., #0 1
FAIL: gcc.target/arm/pr42835.c scan-assembler-times moveq[t ]*r.,[t ]*#
1
FAIL: gcc.target/arm/pr42835.c scan-assembler-times movne[t ]*r.,[t ]*#
1
FAIL: gcc.target/arm/shiftable.c scan-assembler sub.*[al]sl #6
FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler asreq
FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler lslne
FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler asrne
FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler lslne
FAIL: gcc.target/arm/vseleqdf.c scan-assembler-times vseleq.f64\\td[0-9]+ 1
FAIL: gcc.target/arm/vseleqsf.c scan-assembler-times vseleq.f32\\ts[0-9]+ 1
FAIL: gcc.target/arm/vselgedf.c scan-assembler-times vselge.f64\\td[0-9]+ 1
FAIL: gcc.target/arm/vselgesf.c scan-assembler-times vselge.f32\\ts[0-9]+ 1
FAIL: gcc.target/arm/vselgtdf.c scan-assembler-times vselgt.f64\\td[0-9]+ 1
FAIL: gcc.target/arm/vselgtsf.c scan-assembler-times vselgt.f32\\ts[0-9]+ 1
FAIL: gcc.target/arm/vselledf.c scan-assembler-times vselgt.f64\\td[0-9]+ 1
FAIL: gcc.target/arm/vsellesf.c scan-assembler-times vselgt.f32\\ts[0-9]+ 1
FAIL: gcc.target/arm/vselltdf.c scan-assembler-times vselge.f64\\td[0-9]+ 1
FAIL: gcc.target/arm/vselltsf.c scan-assembler-times vselge.f32\\ts[0-9]+ 1
FAIL: gcc.target/arm/vselnedf.c scan-assembler-times vseleq.f64\\td[0-9]+ 1
FAIL: gcc.target/arm/vselnesf.c scan-assembler-times vseleq.f32\\ts[0-9]+ 1
FAIL: gcc.target/arm/vselvcdf.c scan-assembler-times vselvs.f64\\td[0-9]+ 1
FAIL: gcc.target/arm/vselvcsf.c scan-assembler-times vselvs.f32\\ts[0-9]+ 1
FAIL: gcc.target/arm/vselvsdf.c scan-assembler-times vselvs.f64\\td[0-9]+ 1
FAIL: gcc.target/arm/vselvssf.c scan-assembler-times vselvs.f32\\ts[0-9]+ 1
OK?
ChangeLog:
* opts.c (OPT_fif_conversion, OPT_fif_conversion2): Disable for Og.
diff --git a/gcc/opts.c b/gcc/opts.c
index fdc903f..3f3db1a 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -431,8 +431,8 @@ static const struct default_options default_options_table[]
=
{ OPT_LEVELS_1_PLUS, OPT_fguess_branch_probability, NULL, 1 },
{ OPT_LEVELS_1_PLUS, OPT_fcprop_registers, NULL, 1 },
{ OPT_LEVELS_1_PLUS, OPT_fforward_propagate, NULL, 1 },
-{ OPT_LEVELS_1_PLUS, OPT_fif_conversion, NULL, 1 },
-{ OPT_LEVELS_1_PLUS, OPT_fif_conversion2, NULL, 1 },
+{ OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fif_conversion, NULL, 1 },
+{ OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fif_conversion2, NULL, 1 },
{ OPT_LEVELS_1_PLUS, OPT_fipa_pure_const, NULL, 1 },
{ OPT_LEVELS_1_PLUS, OPT_fipa_reference, NULL, 1 },
{ OPT_LEVELS_1_PLUS, OPT_fipa_profile, NULL, 1 },
Re: [patch] Disable if_conversion2 for Og
On Wed, Apr 16, 2014 at 9:46 AM, Joey Ye wrote:
>
>
>> -Original Message-
>> From: Joey Ye [mailto:joey...@arm.com]
>> Sent: Tuesday, April 15, 2014 6:37 PM
>> To: 'Richard Biener'
>> Cc: GCC Patches
>> Subject: RE: [patch] Disable if_conversion2 for Og
>>
>> > Ok for trunk and branches after a while. Why does if-conversion not have
>> > the same problem? On the GIMPLE part we avoid all kinds of if-conversion
>> > with -Og.
>> I think if-conversion should be disabled for Og too, but I don't have a case
>> to
>> show that it is harmful. If GIMPLE avoids all if-conversion, it is nature to
>> do
>> the same for RTL. I'll test and send another patch to also disable
>> if-conversion.
> New patch tested with more regressions with -Og, which are expected.
> FAIL: gcc.target/arm/its.c scan-assembler-times \\tit 2
> FAIL: gcc.target/arm/pr40956.c scan-assembler-times mov[t ]*r., #0 1
> FAIL: gcc.target/arm/pr42835.c scan-assembler-times moveq[t ]*r.,[t
> ]*# 1
> FAIL: gcc.target/arm/pr42835.c scan-assembler-times movne[t ]*r.,[t
> ]*# 1
> FAIL: gcc.target/arm/shiftable.c scan-assembler sub.*[al]sl #6
> FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler asreq
> FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler lslne
> FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler asrne
> FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler lslne
> FAIL: gcc.target/arm/vseleqdf.c scan-assembler-times vseleq.f64\\td[0-9]+ 1
> FAIL: gcc.target/arm/vseleqsf.c scan-assembler-times vseleq.f32\\ts[0-9]+ 1
> FAIL: gcc.target/arm/vselgedf.c scan-assembler-times vselge.f64\\td[0-9]+ 1
> FAIL: gcc.target/arm/vselgesf.c scan-assembler-times vselge.f32\\ts[0-9]+ 1
> FAIL: gcc.target/arm/vselgtdf.c scan-assembler-times vselgt.f64\\td[0-9]+ 1
> FAIL: gcc.target/arm/vselgtsf.c scan-assembler-times vselgt.f32\\ts[0-9]+ 1
> FAIL: gcc.target/arm/vselledf.c scan-assembler-times vselgt.f64\\td[0-9]+ 1
> FAIL: gcc.target/arm/vsellesf.c scan-assembler-times vselgt.f32\\ts[0-9]+ 1
> FAIL: gcc.target/arm/vselltdf.c scan-assembler-times vselge.f64\\td[0-9]+ 1
> FAIL: gcc.target/arm/vselltsf.c scan-assembler-times vselge.f32\\ts[0-9]+ 1
> FAIL: gcc.target/arm/vselnedf.c scan-assembler-times vseleq.f64\\td[0-9]+ 1
> FAIL: gcc.target/arm/vselnesf.c scan-assembler-times vseleq.f32\\ts[0-9]+ 1
> FAIL: gcc.target/arm/vselvcdf.c scan-assembler-times vselvs.f64\\td[0-9]+ 1
> FAIL: gcc.target/arm/vselvcsf.c scan-assembler-times vselvs.f32\\ts[0-9]+ 1
> FAIL: gcc.target/arm/vselvsdf.c scan-assembler-times vselvs.f64\\td[0-9]+ 1
> FAIL: gcc.target/arm/vselvssf.c scan-assembler-times vselvs.f32\\ts[0-9]+ 1
>
> OK?
I suppose the tests above are usually not run with -Og thus the patch
won't regress regular testing.
Ok for trunk.
Thanks,
Richard.
> ChangeLog:
> * opts.c (OPT_fif_conversion, OPT_fif_conversion2): Disable for Og.
>
> diff --git a/gcc/opts.c b/gcc/opts.c
> index fdc903f..3f3db1a 100644
> --- a/gcc/opts.c
> +++ b/gcc/opts.c
> @@ -431,8 +431,8 @@ static const struct default_options
> default_options_table[] =
> { OPT_LEVELS_1_PLUS, OPT_fguess_branch_probability, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fcprop_registers, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fforward_propagate, NULL, 1 },
> -{ OPT_LEVELS_1_PLUS, OPT_fif_conversion, NULL, 1 },
> -{ OPT_LEVELS_1_PLUS, OPT_fif_conversion2, NULL, 1 },
> +{ OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fif_conversion, NULL, 1 },
> +{ OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fif_conversion2, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fipa_pure_const, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fipa_reference, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fipa_profile, NULL, 1 },
>
>
Re: [patch] Disable if_conversion2 for Og
On 15/04/14 02:59, Joey Ye wrote:
> If-converstion is harmful to optimized debugging as it generates conditional
> execution instructions with line number information, which resulted in a
> dillusion to developers that both then-else branches are executed.
>
> For example:
> test.c:
> 1: unsigned oldest_sequence;
> 2:
> 3: unsigned foo(unsigned seq_number)
> 4: {
> 5: if ((seq_number + 5) < 10)
> 6:seq_number += 100;
> 7: else
> 8: seq_number = oldest_sequence;
>
> if (seq_number < oldest_sequence)
> seq_number = oldest_sequence;
>
> return seq_number;
> }
Arguably, this is a bug in gdb. The debugger should understand when a
breakpointed conditional instruction is not going to execute and
silently continue. That preserves the illusion of not executing the
code without requiring the compiler to de-optimize things.
R.
>
> $ arm-none-eabi-gcc -mthumb -mcpu=cortex-m3 -Og -g3
> gets:
> .loc 1 5 0
> addsr3, r0, #5
> cmp r3, #9
> .loc 1 6 0 <- line 6, then branch
> iteels
> addls r0, r0, #100
> .LVL1:
> .loc 1 8 0 <- line 8, else branch. Both branches seems to
> be executed in GDB
> ldrhi r3, .L5
> ldrhi r0, [r3]
>
> The reason is that if_conversion2 is still enabled in Og. The patch simply
> disables it for Og.
>
> Tests:
> * -Og bootstrap passed.
> * Make check default (no additional option): No regression.
> * Make check with -Og: expected regressions. Cases relying on if-conversion2
> failed.
>> FAIL: gcc.target/arm/its.c scan-assembler-times \\tit 2
>> FAIL: gcc.target/arm/pr40956.c scan-assembler-times mov[t ]*r., #0 1
>> FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler asreq
>> FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler lslne
>> FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler asrne
>> FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler lslne
>
> OK to trunk and 4.8/4.9 branch?
>
> ChangeLog:
> * opts.c (OPT_fif_conversion2): Disable for Og.
>
> diff --git a/gcc/opts.c b/gcc/opts.c
> index fdc903f..e076253 100644
> --- a/gcc/opts.c
> +++ b/gcc/opts.c
> @@ -432,7 +432,7 @@ static const struct default_options
> default_options_table[] =
> { OPT_LEVELS_1_PLUS, OPT_fcprop_registers, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fforward_propagate, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fif_conversion, NULL, 1 },
> -{ OPT_LEVELS_1_PLUS, OPT_fif_conversion2, NULL, 1 },
> +{ OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fif_conversion2, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fipa_pure_const, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fipa_reference, NULL, 1 },
> { OPT_LEVELS_1_PLUS, OPT_fipa_profile, NULL, 1 },
>
>
>
Re: [patch] Disable if_conversion2 for Og
On 16/04/14 10:30, Richard Biener wrote:
> On Wed, Apr 16, 2014 at 9:46 AM, Joey Ye wrote:
>>
>>
>>> -Original Message-
>>> From: Joey Ye [mailto:joey...@arm.com]
>>> Sent: Tuesday, April 15, 2014 6:37 PM
>>> To: 'Richard Biener'
>>> Cc: GCC Patches
>>> Subject: RE: [patch] Disable if_conversion2 for Og
>>>
>>>> Ok for trunk and branches after a while. Why does if-conversion not have
>>>> the same problem? On the GIMPLE part we avoid all kinds of if-conversion
>>>> with -Og.
>>> I think if-conversion should be disabled for Og too, but I don't have a
>>> case to
>>> show that it is harmful. If GIMPLE avoids all if-conversion, it is nature
>>> to do
>>> the same for RTL. I'll test and send another patch to also disable
>>> if-conversion.
>> New patch tested with more regressions with -Og, which are expected.
>> FAIL: gcc.target/arm/its.c scan-assembler-times \\tit 2
>> FAIL: gcc.target/arm/pr40956.c scan-assembler-times mov[t ]*r., #0 1
>> FAIL: gcc.target/arm/pr42835.c scan-assembler-times moveq[t ]*r.,[t
>> ]*# 1
>> FAIL: gcc.target/arm/pr42835.c scan-assembler-times movne[t ]*r.,[t
>> ]*# 1
>> FAIL: gcc.target/arm/shiftable.c scan-assembler sub.*[al]sl #6
>> FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler asreq
>> FAIL: gcc.target/arm/thumb-ifcvt-2.c scan-assembler lslne
>> FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler asrne
>> FAIL: gcc.target/arm/thumb-ifcvt.c scan-assembler lslne
>> FAIL: gcc.target/arm/vseleqdf.c scan-assembler-times vseleq.f64\\td[0-9]+ 1
>> FAIL: gcc.target/arm/vseleqsf.c scan-assembler-times vseleq.f32\\ts[0-9]+ 1
>> FAIL: gcc.target/arm/vselgedf.c scan-assembler-times vselge.f64\\td[0-9]+ 1
>> FAIL: gcc.target/arm/vselgesf.c scan-assembler-times vselge.f32\\ts[0-9]+ 1
>> FAIL: gcc.target/arm/vselgtdf.c scan-assembler-times vselgt.f64\\td[0-9]+ 1
>> FAIL: gcc.target/arm/vselgtsf.c scan-assembler-times vselgt.f32\\ts[0-9]+ 1
>> FAIL: gcc.target/arm/vselledf.c scan-assembler-times vselgt.f64\\td[0-9]+ 1
>> FAIL: gcc.target/arm/vsellesf.c scan-assembler-times vselgt.f32\\ts[0-9]+ 1
>> FAIL: gcc.target/arm/vselltdf.c scan-assembler-times vselge.f64\\td[0-9]+ 1
>> FAIL: gcc.target/arm/vselltsf.c scan-assembler-times vselge.f32\\ts[0-9]+ 1
>> FAIL: gcc.target/arm/vselnedf.c scan-assembler-times vseleq.f64\\td[0-9]+ 1
>> FAIL: gcc.target/arm/vselnesf.c scan-assembler-times vseleq.f32\\ts[0-9]+ 1
>> FAIL: gcc.target/arm/vselvcdf.c scan-assembler-times vselvs.f64\\td[0-9]+ 1
>> FAIL: gcc.target/arm/vselvcsf.c scan-assembler-times vselvs.f32\\ts[0-9]+ 1
>> FAIL: gcc.target/arm/vselvsdf.c scan-assembler-times vselvs.f64\\td[0-9]+ 1
>> FAIL: gcc.target/arm/vselvssf.c scan-assembler-times vselvs.f32\\ts[0-9]+ 1
>>
>> OK?
>
> I suppose the tests above are usually not run with -Og thus the patch
> won't regress regular testing.
>
> Ok for trunk.
I'd like to see these tests fixed to ensure that they're skipped if this
goes in.
R.
>
> Thanks,
> Richard.
>
>> ChangeLog:
>> * opts.c (OPT_fif_conversion, OPT_fif_conversion2): Disable for Og.
>>
>> diff --git a/gcc/opts.c b/gcc/opts.c
>> index fdc903f..3f3db1a 100644
>> --- a/gcc/opts.c
>> +++ b/gcc/opts.c
>> @@ -431,8 +431,8 @@ static const struct default_options
>> default_options_table[] =
>> { OPT_LEVELS_1_PLUS, OPT_fguess_branch_probability, NULL, 1 },
>> { OPT_LEVELS_1_PLUS, OPT_fcprop_registers, NULL, 1 },
>> { OPT_LEVELS_1_PLUS, OPT_fforward_propagate, NULL, 1 },
>> -{ OPT_LEVELS_1_PLUS, OPT_fif_conversion, NULL, 1 },
>> -{ OPT_LEVELS_1_PLUS, OPT_fif_conversion2, NULL, 1 },
>> +{ OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fif_conversion, NULL, 1 },
>> +{ OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fif_conversion2, NULL, 1 },
>> { OPT_LEVELS_1_PLUS, OPT_fipa_pure_const, NULL, 1 },
>> { OPT_LEVELS_1_PLUS, OPT_fipa_reference, NULL, 1 },
>> { OPT_LEVELS_1_PLUS, OPT_fipa_profile, NULL, 1 },
>>
>>
>
RE: [patch] Disable if_conversion2 for Og
> -Original Message- > From: Richard Earnshaw > Sent: Wednesday, April 16, 2014 5:44 PM > To: Joey Ye > Cc: gcc-patches@gcc.gnu.org > Subject: Re: [patch] Disable if_conversion2 for Og > > Arguably, this is a bug in gdb. The debugger should understand when a > breakpointed conditional instruction is not going to execute and silently > continue. That preserves the illusion of not executing the code without > requiring the compiler to de-optimize things. > > R. Or compiler just optimizes it, and emits generic DWARFx information to help GDB handle it in more target independently? - Joey
Re: [patch] Disable if_conversion2 for Og
On 16/04/14 11:02, Joey Ye wrote: > > >> -Original Message- >> From: Richard Earnshaw >> Sent: Wednesday, April 16, 2014 5:44 PM >> To: Joey Ye >> Cc: gcc-patches@gcc.gnu.org >> Subject: Re: [patch] Disable if_conversion2 for Og >> >> Arguably, this is a bug in gdb. The debugger should understand when a >> breakpointed conditional instruction is not going to execute and silently >> continue. That preserves the illusion of not executing the code without >> requiring the compiler to de-optimize things. >> >> R. > Or compiler just optimizes it, and emits generic DWARFx information to help > GDB handle it in more target independently? > > - Joey > I'm not sure extra dwarf info would help much. The debugger still has to understand that the breakpoint has not really been hit. R.
Re: [patch] Disable if_conversion2 for Og
On 16/04/14 11:17, Joey Ye wrote: >> -Original Message- >> From: Richard Earnshaw >> Sent: Wednesday, April 16, 2014 6:04 PM >> To: Joey Ye >> Cc: gcc-patches@gcc.gnu.org >> Subject: Re: [patch] Disable if_conversion2 for Og >> >> On 16/04/14 11:02, Joey Ye wrote: >>> >>> >>>> -Original Message- >>>> From: Richard Earnshaw >>>> Sent: Wednesday, April 16, 2014 5:44 PM >>>> To: Joey Ye >>>> Cc: gcc-patches@gcc.gnu.org >>>> Subject: Re: [patch] Disable if_conversion2 for Og >>>> >>>> Arguably, this is a bug in gdb. The debugger should understand when >>>> a breakpointed conditional instruction is not going to execute and >>>> silently continue. That preserves the illusion of not executing the >>>> code without requiring the compiler to de-optimize things. >>>> >>>> R. >>> Or compiler just optimizes it, and emits generic DWARFx information to >>> help GDB handle it in more target independently? >>> >>> - Joey >>> >> >> I'm not sure extra dwarf info would help much. The debugger still has to >> understand that the breakpoint has not really been hit. >> >> R. > Yes, it is inevitable. But without extra dwarf info it will be even more > painful: each time setting break-point or break-point hits it has to decode > the break-pointed instructions and its context to search for conditional > execution and IT blocks. > For thumb code it can get the conditional information it needs from the IT state in the PSR; for ARM code it has to look no further than the instruction itself. R.
RE: [patch] Disable if_conversion2 for Og
> -Original Message- > From: Richard Earnshaw > Sent: Wednesday, April 16, 2014 6:04 PM > To: Joey Ye > Cc: gcc-patches@gcc.gnu.org > Subject: Re: [patch] Disable if_conversion2 for Og > > On 16/04/14 11:02, Joey Ye wrote: > > > > > >> -Original Message- > >> From: Richard Earnshaw > >> Sent: Wednesday, April 16, 2014 5:44 PM > >> To: Joey Ye > >> Cc: gcc-patches@gcc.gnu.org > >> Subject: Re: [patch] Disable if_conversion2 for Og > >> > >> Arguably, this is a bug in gdb. The debugger should understand when > >> a breakpointed conditional instruction is not going to execute and > >> silently continue. That preserves the illusion of not executing the > >> code without requiring the compiler to de-optimize things. > >> > >> R. > > Or compiler just optimizes it, and emits generic DWARFx information to > > help GDB handle it in more target independently? > > > > - Joey > > > > I'm not sure extra dwarf info would help much. The debugger still has to > understand that the breakpoint has not really been hit. > > R. Yes, it is inevitable. But without extra dwarf info it will be even more painful: each time setting break-point or break-point hits it has to decode the break-pointed instructions and its context to search for conditional execution and IT blocks. - Joey
RE: [patch] Disable if_conversion2 for Og
> -Original Message- > From: Richard Earnshaw > Sent: Wednesday, April 16, 2014 6:21 PM > To: Joey Ye > Cc: gcc-patches@gcc.gnu.org > Subject: Re: [patch] Disable if_conversion2 for Og > > On 16/04/14 11:17, Joey Ye wrote: > >> -Original Message- > >> From: Richard Earnshaw > >> Sent: Wednesday, April 16, 2014 6:04 PM > >> To: Joey Ye > >> Cc: gcc-patches@gcc.gnu.org > >> Subject: Re: [patch] Disable if_conversion2 for Og > >> > >> On 16/04/14 11:02, Joey Ye wrote: > >>> > >>> > >>>> -Original Message- > >>>> From: Richard Earnshaw > >>>> Sent: Wednesday, April 16, 2014 5:44 PM > >>>> To: Joey Ye > >>>> Cc: gcc-patches@gcc.gnu.org > >>>> Subject: Re: [patch] Disable if_conversion2 for Og > >>>> > >>>> Arguably, this is a bug in gdb. The debugger should understand > >>>> when a breakpointed conditional instruction is not going to execute > >>>> and silently continue. That preserves the illusion of not > >>>> executing the code without requiring the compiler to de-optimize > things. > >>>> > >>>> R. > >>> Or compiler just optimizes it, and emits generic DWARFx information > >>> to help GDB handle it in more target independently? > >>> > >>> - Joey > >>> > >> > >> I'm not sure extra dwarf info would help much. The debugger still > >> has to understand that the breakpoint has not really been hit. > >> > >> R. > > Yes, it is inevitable. But without extra dwarf info it will be even more painful: > each time setting break-point or break-point hits it has to decode the break- > pointed instructions and its context to search for conditional execution and IT > blocks. > > > > For thumb code it can get the conditional information it needs from the IT > state in the PSR; for ARM code it has to look no further than the instruction > itself. > > R. The thing is, debugger has to do this for every breakpoint, even though more of them are not conditional execution, which isn't efficient.
Re: [patch] Disable if_conversion2 for Og
On 16/04/14 11:30, Joey Ye wrote: > > >> -Original Message- >> From: Richard Earnshaw >> Sent: Wednesday, April 16, 2014 6:21 PM >> To: Joey Ye >> Cc: gcc-patches@gcc.gnu.org >> Subject: Re: [patch] Disable if_conversion2 for Og >> >> On 16/04/14 11:17, Joey Ye wrote: >>>> -Original Message- >>>> From: Richard Earnshaw >>>> Sent: Wednesday, April 16, 2014 6:04 PM >>>> To: Joey Ye >>>> Cc: gcc-patches@gcc.gnu.org >>>> Subject: Re: [patch] Disable if_conversion2 for Og >>>> >>>> On 16/04/14 11:02, Joey Ye wrote: >>>>> >>>>> >>>>>> -Original Message- >>>>>> From: Richard Earnshaw >>>>>> Sent: Wednesday, April 16, 2014 5:44 PM >>>>>> To: Joey Ye >>>>>> Cc: gcc-patches@gcc.gnu.org >>>>>> Subject: Re: [patch] Disable if_conversion2 for Og >>>>>> >>>>>> Arguably, this is a bug in gdb. The debugger should understand >>>>>> when a breakpointed conditional instruction is not going to execute >>>>>> and silently continue. That preserves the illusion of not >>>>>> executing the code without requiring the compiler to de-optimize >> things. >>>>>> >>>>>> R. >>>>> Or compiler just optimizes it, and emits generic DWARFx information >>>>> to help GDB handle it in more target independently? >>>>> >>>>> - Joey >>>>> >>>> >>>> I'm not sure extra dwarf info would help much. The debugger still >>>> has to understand that the breakpoint has not really been hit. >>>> >>>> R. >>> Yes, it is inevitable. But without extra dwarf info it will be even more > painful: >> each time setting break-point or break-point hits it has to decode the > break- >> pointed instructions and its context to search for conditional execution > and IT >> blocks. >>> >> >> For thumb code it can get the conditional information it needs from the IT >> state in the PSR; for ARM code it has to look no further than the > instruction >> itself. >> >> R. > The thing is, debugger has to do this for every breakpoint, even though more > of them are not conditional execution, which isn't efficient. > > Then cache whether the instruction might be conditional when it's created. That's more work when creating the bp (and you do have to scan back to check if a thumb instruction might be made conditional with IT), but would save time when hitting it. Anyway, this is getting off-topic for the GCC-patches list. R.
