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[Qemu-devel] [PATCH] softfloat: rename make_float[x80|128]_init to const_float[x80|128]

Laurent Vivier posted 1 patch 6 years, 7 months ago
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git fetch https://github.com/patchew-project/qemu tags/patchew/20170918104624.14743-1-laurent@vivier.eu
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include/fpu/softfloat.h  | 10 ++++++----
target/m68k/fpu_helper.c | 44 ++++++++++++++++++++++----------------------
2 files changed, 28 insertions(+), 26 deletions(-)
[Qemu-devel] [PATCH] softfloat: rename make_float[x80|128]_init to const_float[x80|128]
Posted by Laurent Vivier 6 years, 7 months ago 
We already have const_float16(), const_float32() and const_float64(),
so rename make_floatx80_init() and make_float128_init() as
const_floatx80() and const_float128().

Redefine make_floatx80() and make_float128() as make_float16(),
make_float32() and make_float64() using a variable and not only
a cast.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 include/fpu/softfloat.h  | 10 ++++++----
 target/m68k/fpu_helper.c | 44 ++++++++++++++++++++++----------------------
 2 files changed, 28 insertions(+), 26 deletions(-)

diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
index 0f96a0edd1..2e1a79ebf7 100644
--- a/include/fpu/softfloat.h
+++ b/include/fpu/softfloat.h
@@ -146,8 +146,9 @@ typedef struct {
     uint64_t low;
     uint16_t high;
 } floatx80;
-#define make_floatx80(exp, mant) ((floatx80) { mant, exp })
-#define make_floatx80_init(exp, mant) { .low = mant, .high = exp }
+#define make_floatx80(exp, mant) __extension__ \
+    ({ floatx80 f80_val = { .low = mant, .high = exp }; f80_val; })
+#define const_floatx80(exp, mant) { .low = mant, .high = exp }
 typedef struct {
 #ifdef HOST_WORDS_BIGENDIAN
     uint64_t high, low;
@@ -155,8 +156,9 @@ typedef struct {
     uint64_t low, high;
 #endif
 } float128;
-#define make_float128(high_, low_) ((float128) { .high = high_, .low = low_ })
-#define make_float128_init(high_, low_) { .high = high_, .low = low_ }
+#define make_float128(high_, low_) __extension__ \
+    ({float128 f128_val = { .high = high_, .low = low_ }; f128_val; })
+#define const_float128(high_, low_) { .high = high_, .low = low_ }
 
 /*----------------------------------------------------------------------------
 | Software IEC/IEEE floating-point underflow tininess-detection mode.
diff --git a/target/m68k/fpu_helper.c b/target/m68k/fpu_helper.c
index 665e7609af..bf62cf8003 100644
--- a/target/m68k/fpu_helper.c
+++ b/target/m68k/fpu_helper.c
@@ -29,28 +29,28 @@
  */
 
 static const floatx80 fpu_rom[128] = {
-    [0x00] = make_floatx80_init(0x4000, 0xc90fdaa22168c235ULL),  /* Pi       */
-    [0x0b] = make_floatx80_init(0x3ffd, 0x9a209a84fbcff798ULL),  /* Log10(2) */
-    [0x0c] = make_floatx80_init(0x4000, 0xadf85458a2bb4a9aULL),  /* e        */
-    [0x0d] = make_floatx80_init(0x3fff, 0xb8aa3b295c17f0bcULL),  /* Log2(e)  */
-    [0x0e] = make_floatx80_init(0x3ffd, 0xde5bd8a937287195ULL),  /* Log10(e) */
-    [0x0f] = make_floatx80_init(0x0000, 0x0000000000000000ULL),  /* Zero     */
-    [0x30] = make_floatx80_init(0x3ffe, 0xb17217f7d1cf79acULL),  /* ln(2)    */
-    [0x31] = make_floatx80_init(0x4000, 0x935d8dddaaa8ac17ULL),  /* ln(10)   */
-    [0x32] = make_floatx80_init(0x3fff, 0x8000000000000000ULL),  /* 10^0     */
-    [0x33] = make_floatx80_init(0x4002, 0xa000000000000000ULL),  /* 10^1     */
-    [0x34] = make_floatx80_init(0x4005, 0xc800000000000000ULL),  /* 10^2     */
-    [0x35] = make_floatx80_init(0x400c, 0x9c40000000000000ULL),  /* 10^4     */
-    [0x36] = make_floatx80_init(0x4019, 0xbebc200000000000ULL),  /* 10^8     */
-    [0x37] = make_floatx80_init(0x4034, 0x8e1bc9bf04000000ULL),  /* 10^16    */
-    [0x38] = make_floatx80_init(0x4069, 0x9dc5ada82b70b59eULL),  /* 10^32    */
-    [0x39] = make_floatx80_init(0x40d3, 0xc2781f49ffcfa6d5ULL),  /* 10^64    */
-    [0x3a] = make_floatx80_init(0x41a8, 0x93ba47c980e98ce0ULL),  /* 10^128   */
-    [0x3b] = make_floatx80_init(0x4351, 0xaa7eebfb9df9de8eULL),  /* 10^256   */
-    [0x3c] = make_floatx80_init(0x46a3, 0xe319a0aea60e91c7ULL),  /* 10^512   */
-    [0x3d] = make_floatx80_init(0x4d48, 0xc976758681750c17ULL),  /* 10^1024  */
-    [0x3e] = make_floatx80_init(0x5a92, 0x9e8b3b5dc53d5de5ULL),  /* 10^2048  */
-    [0x3f] = make_floatx80_init(0x7525, 0xc46052028a20979bULL),  /* 10^4096  */
+    [0x00] = const_floatx80(0x4000, 0xc90fdaa22168c235ULL),  /* Pi       */
+    [0x0b] = const_floatx80(0x3ffd, 0x9a209a84fbcff798ULL),  /* Log10(2) */
+    [0x0c] = const_floatx80(0x4000, 0xadf85458a2bb4a9aULL),  /* e        */
+    [0x0d] = const_floatx80(0x3fff, 0xb8aa3b295c17f0bcULL),  /* Log2(e)  */
+    [0x0e] = const_floatx80(0x3ffd, 0xde5bd8a937287195ULL),  /* Log10(e) */
+    [0x0f] = const_floatx80(0x0000, 0x0000000000000000ULL),  /* Zero     */
+    [0x30] = const_floatx80(0x3ffe, 0xb17217f7d1cf79acULL),  /* ln(2)    */
+    [0x31] = const_floatx80(0x4000, 0x935d8dddaaa8ac17ULL),  /* ln(10)   */
+    [0x32] = const_floatx80(0x3fff, 0x8000000000000000ULL),  /* 10^0     */
+    [0x33] = const_floatx80(0x4002, 0xa000000000000000ULL),  /* 10^1     */
+    [0x34] = const_floatx80(0x4005, 0xc800000000000000ULL),  /* 10^2     */
+    [0x35] = const_floatx80(0x400c, 0x9c40000000000000ULL),  /* 10^4     */
+    [0x36] = const_floatx80(0x4019, 0xbebc200000000000ULL),  /* 10^8     */
+    [0x37] = const_floatx80(0x4034, 0x8e1bc9bf04000000ULL),  /* 10^16    */
+    [0x38] = const_floatx80(0x4069, 0x9dc5ada82b70b59eULL),  /* 10^32    */
+    [0x39] = const_floatx80(0x40d3, 0xc2781f49ffcfa6d5ULL),  /* 10^64    */
+    [0x3a] = const_floatx80(0x41a8, 0x93ba47c980e98ce0ULL),  /* 10^128   */
+    [0x3b] = const_floatx80(0x4351, 0xaa7eebfb9df9de8eULL),  /* 10^256   */
+    [0x3c] = const_floatx80(0x46a3, 0xe319a0aea60e91c7ULL),  /* 10^512   */
+    [0x3d] = const_floatx80(0x4d48, 0xc976758681750c17ULL),  /* 10^1024  */
+    [0x3e] = const_floatx80(0x5a92, 0x9e8b3b5dc53d5de5ULL),  /* 10^2048  */
+    [0x3f] = const_floatx80(0x7525, 0xc46052028a20979bULL),  /* 10^4096  */
 };
 
 int32_t HELPER(reds32)(CPUM68KState *env, FPReg *val)
-- 
2.13.5
Re: [Qemu-devel] [PATCH] softfloat: rename make_float[x80|128]_init to const_float[x80|128]
Posted by Philippe Mathieu-Daudé 6 years, 7 months ago 
On 09/18/2017 07:46 AM, Laurent Vivier wrote:
> We already have const_float16(), const_float32() and const_float64(),
> so rename make_floatx80_init() and make_float128_init() as
> const_floatx80() and const_float128().
> 
> Redefine make_floatx80() and make_float128() as make_float16(),
> make_float32() and make_float64() using a variable and not only
> a cast.
> 
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> ---
>   include/fpu/softfloat.h  | 10 ++++++----
>   target/m68k/fpu_helper.c | 44 ++++++++++++++++++++++----------------------
>   2 files changed, 28 insertions(+), 26 deletions(-)
> 
> diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
> index 0f96a0edd1..2e1a79ebf7 100644
> --- a/include/fpu/softfloat.h
> +++ b/include/fpu/softfloat.h
> @@ -146,8 +146,9 @@ typedef struct {
>       uint64_t low;
>       uint16_t high;
>   } floatx80;
> -#define make_floatx80(exp, mant) ((floatx80) { mant, exp })
> -#define make_floatx80_init(exp, mant) { .low = mant, .high = exp }
> +#define make_floatx80(exp, mant) __extension__ \
> +    ({ floatx80 f80_val = { .low = mant, .high = exp }; f80_val; })
> +#define const_floatx80(exp, mant) { .low = mant, .high = exp }

cleaner.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

>   typedef struct {
>   #ifdef HOST_WORDS_BIGENDIAN
>       uint64_t high, low;
> @@ -155,8 +156,9 @@ typedef struct {
>       uint64_t low, high;
>   #endif
>   } float128;
> -#define make_float128(high_, low_) ((float128) { .high = high_, .low = low_ })
> -#define make_float128_init(high_, low_) { .high = high_, .low = low_ }
> +#define make_float128(high_, low_) __extension__ \
> +    ({float128 f128_val = { .high = high_, .low = low_ }; f128_val; })
> +#define const_float128(high_, low_) { .high = high_, .low = low_ }
>   
>   /*----------------------------------------------------------------------------
>   | Software IEC/IEEE floating-point underflow tininess-detection mode.
> diff --git a/target/m68k/fpu_helper.c b/target/m68k/fpu_helper.c
> index 665e7609af..bf62cf8003 100644
> --- a/target/m68k/fpu_helper.c
> +++ b/target/m68k/fpu_helper.c
> @@ -29,28 +29,28 @@
>    */
>   
>   static const floatx80 fpu_rom[128] = {
> -    [0x00] = make_floatx80_init(0x4000, 0xc90fdaa22168c235ULL),  /* Pi       */
> -    [0x0b] = make_floatx80_init(0x3ffd, 0x9a209a84fbcff798ULL),  /* Log10(2) */
> -    [0x0c] = make_floatx80_init(0x4000, 0xadf85458a2bb4a9aULL),  /* e        */
> -    [0x0d] = make_floatx80_init(0x3fff, 0xb8aa3b295c17f0bcULL),  /* Log2(e)  */
> -    [0x0e] = make_floatx80_init(0x3ffd, 0xde5bd8a937287195ULL),  /* Log10(e) */
> -    [0x0f] = make_floatx80_init(0x0000, 0x0000000000000000ULL),  /* Zero     */
> -    [0x30] = make_floatx80_init(0x3ffe, 0xb17217f7d1cf79acULL),  /* ln(2)    */
> -    [0x31] = make_floatx80_init(0x4000, 0x935d8dddaaa8ac17ULL),  /* ln(10)   */
> -    [0x32] = make_floatx80_init(0x3fff, 0x8000000000000000ULL),  /* 10^0     */
> -    [0x33] = make_floatx80_init(0x4002, 0xa000000000000000ULL),  /* 10^1     */
> -    [0x34] = make_floatx80_init(0x4005, 0xc800000000000000ULL),  /* 10^2     */
> -    [0x35] = make_floatx80_init(0x400c, 0x9c40000000000000ULL),  /* 10^4     */
> -    [0x36] = make_floatx80_init(0x4019, 0xbebc200000000000ULL),  /* 10^8     */
> -    [0x37] = make_floatx80_init(0x4034, 0x8e1bc9bf04000000ULL),  /* 10^16    */
> -    [0x38] = make_floatx80_init(0x4069, 0x9dc5ada82b70b59eULL),  /* 10^32    */
> -    [0x39] = make_floatx80_init(0x40d3, 0xc2781f49ffcfa6d5ULL),  /* 10^64    */
> -    [0x3a] = make_floatx80_init(0x41a8, 0x93ba47c980e98ce0ULL),  /* 10^128   */
> -    [0x3b] = make_floatx80_init(0x4351, 0xaa7eebfb9df9de8eULL),  /* 10^256   */
> -    [0x3c] = make_floatx80_init(0x46a3, 0xe319a0aea60e91c7ULL),  /* 10^512   */
> -    [0x3d] = make_floatx80_init(0x4d48, 0xc976758681750c17ULL),  /* 10^1024  */
> -    [0x3e] = make_floatx80_init(0x5a92, 0x9e8b3b5dc53d5de5ULL),  /* 10^2048  */
> -    [0x3f] = make_floatx80_init(0x7525, 0xc46052028a20979bULL),  /* 10^4096  */
> +    [0x00] = const_floatx80(0x4000, 0xc90fdaa22168c235ULL),  /* Pi       */
> +    [0x0b] = const_floatx80(0x3ffd, 0x9a209a84fbcff798ULL),  /* Log10(2) */
> +    [0x0c] = const_floatx80(0x4000, 0xadf85458a2bb4a9aULL),  /* e        */
> +    [0x0d] = const_floatx80(0x3fff, 0xb8aa3b295c17f0bcULL),  /* Log2(e)  */
> +    [0x0e] = const_floatx80(0x3ffd, 0xde5bd8a937287195ULL),  /* Log10(e) */
> +    [0x0f] = const_floatx80(0x0000, 0x0000000000000000ULL),  /* Zero     */
> +    [0x30] = const_floatx80(0x3ffe, 0xb17217f7d1cf79acULL),  /* ln(2)    */
> +    [0x31] = const_floatx80(0x4000, 0x935d8dddaaa8ac17ULL),  /* ln(10)   */
> +    [0x32] = const_floatx80(0x3fff, 0x8000000000000000ULL),  /* 10^0     */
> +    [0x33] = const_floatx80(0x4002, 0xa000000000000000ULL),  /* 10^1     */
> +    [0x34] = const_floatx80(0x4005, 0xc800000000000000ULL),  /* 10^2     */
> +    [0x35] = const_floatx80(0x400c, 0x9c40000000000000ULL),  /* 10^4     */
> +    [0x36] = const_floatx80(0x4019, 0xbebc200000000000ULL),  /* 10^8     */
> +    [0x37] = const_floatx80(0x4034, 0x8e1bc9bf04000000ULL),  /* 10^16    */
> +    [0x38] = const_floatx80(0x4069, 0x9dc5ada82b70b59eULL),  /* 10^32    */
> +    [0x39] = const_floatx80(0x40d3, 0xc2781f49ffcfa6d5ULL),  /* 10^64    */
> +    [0x3a] = const_floatx80(0x41a8, 0x93ba47c980e98ce0ULL),  /* 10^128   */
> +    [0x3b] = const_floatx80(0x4351, 0xaa7eebfb9df9de8eULL),  /* 10^256   */
> +    [0x3c] = const_floatx80(0x46a3, 0xe319a0aea60e91c7ULL),  /* 10^512   */
> +    [0x3d] = const_floatx80(0x4d48, 0xc976758681750c17ULL),  /* 10^1024  */
> +    [0x3e] = const_floatx80(0x5a92, 0x9e8b3b5dc53d5de5ULL),  /* 10^2048  */
> +    [0x3f] = const_floatx80(0x7525, 0xc46052028a20979bULL),  /* 10^4096  */
>   };
>   
>   int32_t HELPER(reds32)(CPUM68KState *env, FPReg *val)
>
Re: [Qemu-devel] [PATCH] softfloat: rename make_float[x80|128]_init to const_float[x80|128]
Posted by Richard Henderson 6 years, 7 months ago 
On 09/18/2017 05:46 AM, Laurent Vivier wrote:
> Redefine make_floatx80() and make_float128() as make_float16(),
> make_float32() and make_float64() using a variable and not only
> a cast.

I don't like this part -- (type){ init } is a standard C99 compound literal.
There's no point using a gcc extension instead.


r~
Re: [Qemu-devel] [PATCH] softfloat: rename make_float[x80|128]_init to const_float[x80|128]
Posted by Eric Blake 6 years, 7 months ago 
On 09/19/2017 11:30 AM, Richard Henderson wrote:
> On 09/18/2017 05:46 AM, Laurent Vivier wrote:
>> Redefine make_floatx80() and make_float128() as make_float16(),
>> make_float32() and make_float64() using a variable and not only
>> a cast.

>> -#define make_floatx80(exp, mant) ((floatx80) { mant, exp })
>> -#define make_floatx80_init(exp, mant) { .low = mant, .high = exp }
>> +#define make_floatx80(exp, mant) __extension__ \
>> +    ({ floatx80 f80_val = { .low = mant, .high = exp }; f80_val; })
>> +#define const_floatx80(exp, mant) { .low = mant, .high = exp }

> 
> I don't like this part -- (type){ init } is a standard C99 compound literal.
> There's no point using a gcc extension instead.

The C99 compound literal is not a const initializer in all situations,
though :(  Here's another thread where we had a similar discussion, but
there, the solution was to just make the macro behave as an initializer
(which is C99 compliant, but loses some type safety) instead of relying
on a gcc extension:

https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg06566.html

I suspect you're running into the same issues that Laszlo already helped
us understand regarding QLit.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org
Re: [Qemu-devel] [PATCH] softfloat: rename make_float[x80|128]_init to const_float[x80|128]
Posted by Laszlo Ersek 6 years, 7 months ago 
On 09/19/17 19:39, Eric Blake wrote:
> On 09/19/2017 11:30 AM, Richard Henderson wrote:
>> On 09/18/2017 05:46 AM, Laurent Vivier wrote:
>>> Redefine make_floatx80() and make_float128() as make_float16(),
>>> make_float32() and make_float64() using a variable and not only
>>> a cast.
> 
>>> -#define make_floatx80(exp, mant) ((floatx80) { mant, exp })
>>> -#define make_floatx80_init(exp, mant) { .low = mant, .high = exp }
>>> +#define make_floatx80(exp, mant) __extension__ \
>>> +    ({ floatx80 f80_val = { .low = mant, .high = exp }; f80_val; })
>>> +#define const_floatx80(exp, mant) { .low = mant, .high = exp }
> 
>>
>> I don't like this part -- (type){ init } is a standard C99 compound literal.
>> There's no point using a gcc extension instead.
> 
> The C99 compound literal is not a const initializer in all situations,
> though :(  Here's another thread where we had a similar discussion, but
> there, the solution was to just make the macro behave as an initializer
> (which is C99 compliant, but loses some type safety) instead of relying
> on a gcc extension:
> 
> https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg06566.html
> 
> I suspect you're running into the same issues that Laszlo already helped
> us understand regarding QLit.
> 

Thanks for the CC! I don't have much context, but the patch looks quite
isolated.

I think I agree with Richard here -- I don't think there's any reason to
change the replacement text of make_floatx80.

The patch names make_float64() as an earlier example (already using
__extension__), but I don't understand why make_float64() was written
that way. ... It seems to go back to ancient commit f090c9d4ad58 ("Add
strict checking mode for softfp code.", 2007-11-18). Was C99 support
(esp. compound literals) spotty in gcc back then?

Not having much background, I'd suggest the opposite change -- replace
the statement-expression in make_float64() with a compound literal.

Thanks
Laszlo
Re: [Qemu-devel] [PATCH] softfloat: rename make_float[x80|128]_init to const_float[x80|128]
Posted by Laurent Vivier 6 years, 7 months ago 
Le 19/09/2017 à 20:45, Laszlo Ersek a écrit :
> On 09/19/17 19:39, Eric Blake wrote:
>> On 09/19/2017 11:30 AM, Richard Henderson wrote:
>>> On 09/18/2017 05:46 AM, Laurent Vivier wrote:
>>>> Redefine make_floatx80() and make_float128() as make_float16(),
>>>> make_float32() and make_float64() using a variable and not only
>>>> a cast.
>>
>>>> -#define make_floatx80(exp, mant) ((floatx80) { mant, exp })
>>>> -#define make_floatx80_init(exp, mant) { .low = mant, .high = exp }
>>>> +#define make_floatx80(exp, mant) __extension__ \
>>>> +    ({ floatx80 f80_val = { .low = mant, .high = exp }; f80_val; })
>>>> +#define const_floatx80(exp, mant) { .low = mant, .high = exp }
>>
>>>
>>> I don't like this part -- (type){ init } is a standard C99 compound literal.
>>> There's no point using a gcc extension instead.
>>
>> The C99 compound literal is not a const initializer in all situations,
>> though :(  Here's another thread where we had a similar discussion, but
>> there, the solution was to just make the macro behave as an initializer
>> (which is C99 compliant, but loses some type safety) instead of relying
>> on a gcc extension:
>>
>> https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg06566.html
>>
>> I suspect you're running into the same issues that Laszlo already helped
>> us understand regarding QLit.
>>
> 
> Thanks for the CC! I don't have much context, but the patch looks quite
> isolated.
> 
> I think I agree with Richard here -- I don't think there's any reason to
> change the replacement text of make_floatx80.
> 
> The patch names make_float64() as an earlier example (already using
> __extension__), but I don't understand why make_float64() was written
> that way. ... It seems to go back to ancient commit f090c9d4ad58 ("Add
> strict checking mode for softfp code.", 2007-11-18). Was C99 support
> (esp. compound literals) spotty in gcc back then?
> 
> Not having much background, I'd suggest the opposite change -- replace
> the statement-expression in make_float64() with a compound literal.


Okay, I'll do this way.

Thank you all for your comments.

Laurent
Re: [Qemu-devel] [PATCH] softfloat: rename make_float[x80|128]_init to const_float[x80|128]
Posted by Richard Henderson 6 years, 7 months ago 
On 09/19/2017 12:39 PM, Eric Blake wrote:
> On 09/19/2017 11:30 AM, Richard Henderson wrote:
>> On 09/18/2017 05:46 AM, Laurent Vivier wrote:
>>> Redefine make_floatx80() and make_float128() as make_float16(),
>>> make_float32() and make_float64() using a variable and not only
>>> a cast.
> 
>>> -#define make_floatx80(exp, mant) ((floatx80) { mant, exp })
>>> -#define make_floatx80_init(exp, mant) { .low = mant, .high = exp }
>>> +#define make_floatx80(exp, mant) __extension__ \
>>> +    ({ floatx80 f80_val = { .low = mant, .high = exp }; f80_val; })
>>> +#define const_floatx80(exp, mant) { .low = mant, .high = exp }
> 
>>
>> I don't like this part -- (type){ init } is a standard C99 compound literal.
>> There's no point using a gcc extension instead.
> 
> The C99 compound literal is not a const initializer in all situations,
> though :( 

A compound literal not officially a const initializer in any situation.  That
it is accepted by gcc as a const initializer is an extension.

I don't dispute const_floatx80, but the change to make_floatx80.


r~

Patchew 2.1-devel-0870f84

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