[PATCH] Make muser-mode the default for LEON3

[PATCH] Make muser-mode the default for LEON3

[Daniel Cederman]

The muser-mode flag causes the CASA instruction for LEON3 to use the
user mode ASI. This is the correct behavior for almost all LEON3 targets.
For this reason it makes sense to make user mode the default.

gcc/ChangeLog:

2015-06-23  Daniel Cederman  <cederman@gaisler.com>

	* config/sparc/sparc.opt: Rename mask from USER_MODE to SV_MODE
	  and make it inverse to change default
	* config/sparc/sync.md: Only use supervisor ASI for CASA when in
	  supervisor mode
	* doc/invoke.texi: Document change of default
---
 gcc/config/sparc/sparc.opt | 4 ++--
 gcc/config/sparc/sync.md   | 6 +++---
 gcc/doc/invoke.texi        | 4 ++--
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/gcc/config/sparc/sparc.opt b/gcc/config/sparc/sparc.opt
index 93d24a6..85bf0bd 100644
--- a/gcc/config/sparc/sparc.opt
+++ b/gcc/config/sparc/sparc.opt
@@ -114,8 +114,8 @@ Target
 Optimize tail call instructions in assembler and linker
 
 muser-mode
-Target Report Mask(USER_MODE)
-Do not generate code that can only run in supervisor mode
+Target Report InverseMask(SV_MODE)
+Do not generate code that can only run in supervisor mode (default)
 
 mcpu=
 Target RejectNegative Joined Var(sparc_cpu_and_features) Enum(sparc_processor_type) Init(PROCESSOR_V7)
diff --git a/gcc/config/sparc/sync.md b/gcc/config/sparc/sync.md
index 7d00b10..2fabff5 100644
--- a/gcc/config/sparc/sync.md
+++ b/gcc/config/sparc/sync.md
@@ -222,10 +222,10 @@
 	  UNSPECV_CAS))]
   "TARGET_LEON3"
 {
-  if (TARGET_USER_MODE)
-    return "casa\t%1 0xa, %2, %0"; /* ASI for user data space.  */
-  else
+  if (TARGET_SV_MODE)
     return "casa\t%1 0xb, %2, %0"; /* ASI for supervisor data space.  */
+  else
+    return "casa\t%1 0xa, %2, %0"; /* ASI for user data space.  */
 }
   [(set_attr "type" "multi")])
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index b99ab1c..86b2a73 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -21305,8 +21305,8 @@ in a performance loss, especially for floating-point code.
 @opindex muser-mode
 @opindex mno-user-mode
 Do not generate code that can only run in supervisor mode.  This is relevant
-only for the @code{casa} instruction emitted for the LEON3 processor.  The
-default is @option{-mno-user-mode}.
+only for the @code{casa} instruction emitted for the LEON3 processor.  This
+is the default.
 
 @item -mno-faster-structs
 @itemx -mfaster-structs
-- 
2.4.3

Re: [PATCH] Make muser-mode the default for LEON3

[Eric Botcazou]

> The muser-mode flag causes the CASA instruction for LEON3 to use the
> user mode ASI. This is the correct behavior for almost all LEON3 targets.

Do they lack the CASA instruction with supervisor-mode ASI?  What happens when 
the CASA instruction with user-mode ASI is executed in supervisor mode?

-- 
Eric Botcazou

Re: [PATCH] Make muser-mode the default for LEON3

[Daniel Cederman]

>
> Do they lack the CASA instruction with supervisor-mode ASI?  What happens when
> the CASA instruction with user-mode ASI is executed in supervisor mode?
>

For all LEON3 (with CASA support) the CASA instruction works in 
supervisor-mode regardless of ASI used. In user-mode CASA only works 
with the user-mode ASI. So CASA with user-mode ASI works for both 
user-mode and supervisor-mode. By having user-mode ASI as default, one 
would not need to change flag when compiling user or kernel code.

On a few old LEON3 systems the CASA instruction only works in supervisor 
mode. Using the CASA instruction with the user-mode ASI on these systems 
is not legal and will cause a trap.

-- 
Daniel Cederman

Re: [PATCH] Make muser-mode the default for LEON3

[Eric Botcazou]

> For all LEON3 (with CASA support) the CASA instruction works in
> supervisor-mode regardless of ASI used. In user-mode CASA only works
> with the user-mode ASI. So CASA with user-mode ASI works for both
> user-mode and supervisor-mode. By having user-mode ASI as default, one
> would not need to change flag when compiling user or kernel code.

Thanks, OK for mainline, 5 branch and 4.9 branch.

-- 
Eric Botcazou

Re: [PATCH] Make muser-mode the default for LEON3

[Daniel Cederman]

On 2015-06-23 14:58, Jakub Jelinek wrote:
> On Tue, Jun 23, 2015 at 02:48:45PM +0200, Daniel Cederman wrote:
>> How does one check if the bit has been explicitly set? It was not obvious to
>
> if (TARGET_USER_MODE_P (target_flags_explicit))
>
>> me, which is why I took a similar approach to a patch I found for another
>> CPU target. If it is possible to change the default without adding another
>> flag then that is obviously better and I will update my patch.
>
> Or you can just change the default target_flags, supposedly with
> TargetVariable
> int target_flags = MASK_USER_MODE
> in the opt file, there are really many possibilities.
>
> 	Jakub
>

Thanks! I went with your suggestion in the previous mail and removed the 
new -msv-mode option and inversed the user mode mask.

Best regards,
Daniel Cederman

Re: [PATCH] Make muser-mode the default for LEON3

[Jakub Jelinek]

On Tue, Jun 23, 2015 at 02:48:45PM +0200, Daniel Cederman wrote:
> How does one check if the bit has been explicitly set? It was not obvious to

if (TARGET_USER_MODE_P (target_flags_explicit))

> me, which is why I took a similar approach to a patch I found for another
> CPU target. If it is possible to change the default without adding another
> flag then that is obviously better and I will update my patch.

Or you can just change the default target_flags, supposedly with
TargetVariable
int target_flags = MASK_USER_MODE
in the opt file, there are really many possibilities.

	Jakub

Re: [PATCH] Make muser-mode the default for LEON3

[Daniel Cederman]

On 2015-06-23 14:34, Jakub Jelinek wrote:
> On Tue, Jun 23, 2015 at 02:22:34PM +0200, Daniel Cederman wrote:
>> The muser-mode flag causes the CASA instruction for LEON3 to use the
>> user mode ASI. This is the correct behavior for almost all LEON3 targets.
>> For this reason it makes sense to make user mode the default. This patch
>> adds a flag for supervisor mode that can be used on the very few LEON3 targets
>> that requires CASA to use the supervisor ASI.
>
> Why are you adding a new option and without deprecation removing a
> previously accepted (at least since 4.8) option?
> For just changing the default, you really don't need to add a new option
> or remove -mno-user-mode, just change the default, which can be done
> e.g. by checking if the bit has been explicitly set and if not, use the
> desired default, or if you want to change the Mask() name, just
> make it InverseMask, but keep the options as they are.
>
> 	Jakub
>

How does one check if the bit has been explicitly set? It was not 
obvious to me, which is why I took a similar approach to a patch I found 
for another CPU target. If it is possible to change the default without 
adding another flag then that is obviously better and I will update my 
patch.

Best regards,
Daniel Cederman

Re: [PATCH] Make muser-mode the default for LEON3

[Jakub Jelinek]

On Tue, Jun 23, 2015 at 02:22:34PM +0200, Daniel Cederman wrote:
> The muser-mode flag causes the CASA instruction for LEON3 to use the
> user mode ASI. This is the correct behavior for almost all LEON3 targets.
> For this reason it makes sense to make user mode the default. This patch
> adds a flag for supervisor mode that can be used on the very few LEON3 targets
> that requires CASA to use the supervisor ASI.

Why are you adding a new option and without deprecation removing a
previously accepted (at least since 4.8) option?
For just changing the default, you really don't need to add a new option
or remove -mno-user-mode, just change the default, which can be done
e.g. by checking if the bit has been explicitly set and if not, use the
desired default, or if you want to change the Mask() name, just
make it InverseMask, but keep the options as they are.

	Jakub

Re: [PATCH] Make muser-mode the default for LEON3

[Sebastian Huber]

Instead of introducing a new option which may conflict with an existing 
one, is it not possible to simply use -mno-user-mode?

On 23/06/15 14:22, Daniel Cederman wrote:
> The muser-mode flag causes the CASA instruction for LEON3 to use the
> user mode ASI. This is the correct behavior for almost all LEON3 targets.
> For this reason it makes sense to make user mode the default. This patch
> adds a flag for supervisor mode that can be used on the very few LEON3 targets
> that requires CASA to use the supervisor ASI.
>
> gcc/ChangeLog:
>
> 2015-06-22  Daniel Cederman  <cederman@gaisler.com>
>
> 	* config/sparc/sparc.opt: Add supervisor mode flag (-msv-mode) and
> 	  make user mode the default
> 	* config/sparc/sync.md: Only use supervisor ASI for CASA when in
> 	  supervisor mode
> 	* doc/invoke.texi: Document msv-mode flag

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber@embedded-brains.de
PGP     : Public key available on request.

Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.

[PATCH] Make muser-mode the default for LEON3

[Daniel Cederman]

The muser-mode flag causes the CASA instruction for LEON3 to use the
user mode ASI. This is the correct behavior for almost all LEON3 targets.
For this reason it makes sense to make user mode the default. This patch
adds a flag for supervisor mode that can be used on the very few LEON3 targets
that requires CASA to use the supervisor ASI.

gcc/ChangeLog:

2015-06-22  Daniel Cederman  <cederman@gaisler.com>

	* config/sparc/sparc.opt: Add supervisor mode flag (-msv-mode) and
	  make user mode the default
	* config/sparc/sync.md: Only use supervisor ASI for CASA when in
	  supervisor mode
	* doc/invoke.texi: Document msv-mode flag
---
 gcc/config/sparc/sparc.opt |  8 ++++++--
 gcc/config/sparc/sync.md   |  6 +++---
 gcc/doc/invoke.texi        | 13 ++++++++-----
 3 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/gcc/config/sparc/sparc.opt b/gcc/config/sparc/sparc.opt
index 93d24a6..5c7f546 100644
--- a/gcc/config/sparc/sparc.opt
+++ b/gcc/config/sparc/sparc.opt
@@ -113,9 +113,13 @@ mrelax
 Target
 Optimize tail call instructions in assembler and linker
 
+msv-mode
+Target RejectNegative Report Mask(SV_MODE)
+Generate code that can only run in supervisor mode
+
 muser-mode
-Target Report Mask(USER_MODE)
-Do not generate code that can only run in supervisor mode
+Target RejectNegative Report InverseMask(SV_MODE)
+Do not generate code that can only run in supervisor mode (default)
 
 mcpu=
 Target RejectNegative Joined Var(sparc_cpu_and_features) Enum(sparc_processor_type) Init(PROCESSOR_V7)
diff --git a/gcc/config/sparc/sync.md b/gcc/config/sparc/sync.md
index 7d00b10..2fabff5 100644
--- a/gcc/config/sparc/sync.md
+++ b/gcc/config/sparc/sync.md
@@ -222,10 +222,10 @@
 	  UNSPECV_CAS))]
   "TARGET_LEON3"
 {
-  if (TARGET_USER_MODE)
-    return "casa\t%1 0xa, %2, %0"; /* ASI for user data space.  */
-  else
+  if (TARGET_SV_MODE)
     return "casa\t%1 0xb, %2, %0"; /* ASI for supervisor data space.  */
+  else
+    return "casa\t%1 0xa, %2, %0"; /* ASI for user data space.  */
 }
   [(set_attr "type" "multi")])
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index b99ab1c..211e8e9 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1008,7 +1008,7 @@ See RS/6000 and PowerPC Options.
 -mhard-quad-float  -msoft-quad-float @gol
 -mstack-bias  -mno-stack-bias @gol
 -munaligned-doubles  -mno-unaligned-doubles @gol
--muser-mode  -mno-user-mode @gol
+-muser-mode  -msv-mode @gol
 -mv8plus  -mno-v8plus  -mvis  -mno-vis @gol
 -mvis2  -mno-vis2  -mvis3  -mno-vis3 @gol
 -mcbcond -mno-cbcond @gol
@@ -21300,13 +21300,16 @@ Specifying this option avoids some rare compatibility problems with code
 generated by other compilers.  It is not the default because it results
 in a performance loss, especially for floating-point code.
 
+@item -msv-mode
+@opindex msv-mode
+Generate code that can only run in supervisor mode.  This is relevant
+only for the @code{casa} instruction emitted for the LEON3 processor.
+
 @item -muser-mode
-@itemx -mno-user-mode
 @opindex muser-mode
-@opindex mno-user-mode
 Do not generate code that can only run in supervisor mode.  This is relevant
-only for the @code{casa} instruction emitted for the LEON3 processor.  The
-default is @option{-mno-user-mode}.
+only for the @code{casa} instruction emitted for the LEON3 processor.  This
+is the default.
 
 @item -mno-faster-structs
 @itemx -mfaster-structs
-- 
2.4.3