[Pixman] [PATCH 2/3] build: use '-mloongson-mmi' for Loongson MMI.

[Yin Shiyou]

It's suggested to use '-mloongson-mmi' to enable MMI.
Use '-march=loongson2f' will lead a link error in new platform
while config check and then MMI will be disabled.
---
 configure.ac | 2 +-
 meson.build  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index 1ca3974..fd7df47 100644
--- a/configure.ac
+++ b/configure.ac
@@ -273,7 +273,7 @@ dnl 
===
 dnl Check for Loongson Multimedia Instructions
 
 if test "x$LS_CFLAGS" = "x" ; then
-LS_CFLAGS="-march=loongson2f"
+LS_CFLAGS="-mloongson-mmi"
 fi
 
 have_loongson_mmi=no
diff --git a/meson.build b/meson.build
index 15d3409..a45c969 100644
--- a/meson.build
+++ b/meson.build
@@ -51,7 +51,7 @@ endforeach
 
 use_loongson_mmi = get_option('loongson-mmi')
 have_loongson_mmi = false
-loongson_mmi_flags = ['-march=loongson2f']
+loongson_mmi_flags = ['-mloongson-mmi']
 if not use_loongson_mmi.disabled()
   if host_machine.cpu_family() == 'mips64' and cc.compiles('''
   #ifndef __mips_loongson_vector_rev
-- 
2.1.0

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Re: [Pixman] [PATCH] pixman-combine: Fix wrong value of RB_MASK_PLUS_ONE.

[Shiyou Yin]

That's great, the analysis is very detailed.
Macro RB_MASK_PLUS_ONE is mainly used to saturate the 16-bits data to 0xff.
In function UN8_rb_ADD_UN8_rb, it can’t affect the result in the end.


>-Original Message-
>From: Søren Sandmann [mailto:soren.sandm...@gmail.com]
>Sent: Sunday, February 9, 2020 11:44 PM
>To: Shiyou Yin
>Cc: Matt Turner; pixman
>Subject: Re: [Pixman] [PATCH] pixman-combine: Fix wrong value of 
>RB_MASK_PLUS_ONE.
>
>Hi,
>
>The reason this bug doesn't show up in the test suite is that it
>doesn't have an effect on the output. The purpose of the
>UN8_rb_ADD_UN8_rb macro is to add two numbers like these:
>
>00aa00bb
>00cc00dd
>
>together, but to saturate aa+cc and bb+dd to 0xff instead of allowing
>them to overflow. Let's pretend that bb and dd are both zero and focus
>on aa+cc. If that addition does in fact overflow (ie., if aa+cc >
>0xff), the result looks like this:
>
>01??
>
>The macro first detects the overflow shifting this value by 8 and
>masking to 0x00ff00ff:
>
>0001
>
>Then it subtracts this from the RB_MASK_PLUS_ONE value:
>
>with bug:   1000 - 0001 = 0fff
>with bug fix:   0100 - 0001 = 00ff
>
>The macro then ors this value with the original sum:
>
>with bug:0fff | 01?? = 0fff
>with bug fix:00ff | 01?? = 01ff
>
>But then it masks the result with 00ff00ff, and so both with and
>without the bug, the final result is the same:
>
>00ff
>
>which is why the bug doesn't affect the calculation.
>
>
>Søren
>
>
>On Sun, Feb 9, 2020 at 4:26 AM Shiyou Yin  wrote:
>>
>> >-Original Message-
>> >From: Matt Turner [mailto:matts...@gmail.com]
>> >Sent: Sunday, February 9, 2020 7:01 AM
>> >To: Yin Shiyou
>> >Cc: pixman@lists.freedesktop.org
>> >Subject: Re: [Pixman] [PATCH] pixman-combine: Fix wrong value of 
>> >RB_MASK_PLUS_ONE.
>> >
>> >On Mon, Feb 3, 2020 at 1:56 AM Yin Shiyou  wrote:
>> >>
>> >> ---
>> >>  pixman/pixman-combine32.h | 2 +-
>> >>  1 file changed, 1 insertion(+), 1 deletion(-)
>> >>
>> >> diff --git a/pixman/pixman-combine32.h b/pixman/pixman-combine32.h
>> >> index cdd56a6..59bb247 100644
>> >> --- a/pixman/pixman-combine32.h
>> >> +++ b/pixman/pixman-combine32.h
>> >> @@ -12,7 +12,7 @@
>> >>  #define RB_MASK 0xff00ff
>> >>  #define AG_MASK 0xff00ff00
>> >>  #define RB_ONE_HALF 0x800080
>> >> -#define RB_MASK_PLUS_ONE 0x1100
>> >> +#define RB_MASK_PLUS_ONE 0x1000100
>> >
>> >
>> >Thanks. The patch looks correct, but obviously nothing in the test
>> >suite is failing. How did you discover this? Does this patch fix
>> >something for you?
>>
>> I just found this mistake while analyzing macro 'UN8_rb_ADD_UN8_rb'
>> and functions called this macro. I can't verify this error with existing
>> test suite, it all passed no matter Fix it or not.
>>
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>> https://lists.freedesktop.org/mailman/listinfo/pixman

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