Displaying 20 results from an estimated 27 matches for "subclause".
2020 Sep 13
2
Invalid transformation in LibCallSimplifier::replacePowWithSqrt?
...n LibCallSimplifier::replacePowWithSqrt with respect to
-Inf uses a select instruction, which based on the observed behaviour,
incorporates the side effects of the unchosen branch. This means that (for
pow) a call to sqrt(-Inf) is materialized. Such a call is specified as
having a domain error (C17 subclause 7.12.7.5) since the operand is less
than zero. Contrast this with pow(-Inf, 0.5), which is specified by C17
subclause F.10.4.4 as having a result of +Inf (indicating an exact result
for the operation and, since IEEE Std 754-2008 subclause 9.1.1 states that
domain errors are to be indicated by a NaN...
2020 Sep 14
2
Invalid transformation in LibCallSimplifier::replacePowWithSqrt?
...qrt with respect
>> to -Inf uses a select instruction, which based on the observed behaviour,
>> incorporates the side effects of the unchosen branch. This means that (for
>> pow) a call to sqrt(-Inf) is materialized. Such a call is specified as
>> having a domain error (C17 subclause 7.12.7.5) since the operand is less
>> than zero. Contrast this with pow(-Inf, 0.5), which is specified by C17
>> subclause F.10.4.4 as having a result of +Inf (indicating an exact result
>> for the operation and, since IEEE Std 754-2008 subclause 9.1.1 states that
>> domain...
2020 Sep 14
2
Invalid transformation in LibCallSimplifier::replacePowWithSqrt?
...t to -Inf uses a select instruction, which based on the observed
>>>> behaviour, incorporates the side effects of the unchosen branch. This means
>>>> that (for pow) a call to sqrt(-Inf) is materialized. Such a call is
>>>> specified as having a domain error (C17 subclause 7.12.7.5) since the
>>>> operand is less than zero. Contrast this with pow(-Inf, 0.5), which is
>>>> specified by C17 subclause F.10.4.4 as having a result of +Inf (indicating
>>>> an exact result for the operation and, since IEEE Std 754-2008 subclause
>>&...
2007 Mar 22
2
[LLVMdev] a question about constant fold for fdiv
...0.0", the folded result is inf. I
>> think this should be nan. Can anyone tell me why it is not nan?
>>
>
> I think the specification says that it is "undefined" so any value will
> do. inf is just as undefined as nan.
>
> Reid.
In IEEE Std 754-1985, subclause 7.2- Division by Zero, it says:
/"If the divisor is zero and the dividend is a finite nonzero number,
then the division by zero shall be signaled. The result, when no trap
occurs, shall be a correctly signed (infinity symbol)(6.3)."
/So LLVM is correct (assuming it handles signs corre...
2008 May 14
0
[LLVMdev] optimization assumes malloc return is non-null
...eader inclusion.
>>
>> Neil.
>
> What section of the C standard do I need to refresh myself on here?
>
Good question (referring to the original question). The answer
appears to be 7.1.3/1, fourth bullet:
"All identifiers with external linkage in any of the following
subclauses (including the future library directions) are always
reserved for use as identifiers with external linkage."
Daveed
2008 May 14
2
[LLVMdev] optimization assumes malloc return is non-null
On Wed, 2008-05-14 at 23:23 +0900, Neil Booth wrote:
> Jonathan S. Shapiro wrote:-
> > Is there a requirement somewhere in the C *Language* Specification that
> > ties all of this together in the required way?
>
> Reserved identifiers and header inclusion.
>
> Neil.
What section of the C standard do I need to refresh myself on here?
2007 Mar 22
0
[LLVMdev] a question about constant fold for fdiv
...I
>>> think this should be nan. Can anyone tell me why it is not nan?
>>>
>>
>> I think the specification says that it is "undefined" so any value will
>> do. inf is just as undefined as nan.
>>
>> Reid.
>
> In IEEE Std 754-1985, subclause 7.2- Division by Zero, it says:
>
> /"If the divisor is zero and the dividend is a finite nonzero number,
> then the division by zero shall be signaled. The result, when no trap
> occurs, shall be a correctly signed (infinity symbol)(6.3)."
>
> /So LLVM is correct (ass...
2008 May 14
2
[LLVMdev] optimization assumes malloc return is non-null
...tion
> >>> that
> >>> ties all of this together in the required way?
>
> Good question (referring to the original question). The answer
> appears to be 7.1.3/1, fourth bullet:
>
> "All identifiers with external linkage in any of the following
> subclauses (including the future library directions) are always
> reserved for use as identifiers with external linkage."
First, thank you.
I apologize if I have been acting like a language lawyer, but I'm about
to be working on static analysis tools and I'm discovering that my
understand...
2017 Feb 14
2
RFC: Representing unions in TBAA
...is pretty much wrong. You probably mean
>> "necessary for a reasonable interpretation" or something.
>>
>> Because we would be *functionally correct* by the standard by destroying
>> the program if you ever read the member you didn't set :)
>>
> C11 subclause 6.5.2.3 paragraph 3, has in footnote 95:
> If the member used to read the contents of a union object is not the same
> as the member last used to store a value in the object, the appropriate
> part of the object representation of the value is reinterpreted as an
> object representation...
2020 Oct 10
2
Undef and Poison round table follow-up & a plan
>
> Okay, it's just not immediately undefined behaviour. The C model has more
> issues because of the problem with how "trap representation" is defined
> (which precludes trap representations for unsigned char, two's complement
> signed char, etc.).
This interpretation is further stressed because C only explicitly ascribes
> undefined behaviour to trap
2019 May 24
2
Delinearization validity checks in DependenceAnalysis
[CC bollu, mferguson, shil]
Am Do., 23. Mai 2019 um 17:13 Uhr schrieb Bardia Mahjour <
bmahjour at ca.ibm.com>:
> Thanks David and Michael for the clarification.
>
> I think I understand the rational behind those checks in delinearization
> now.
>
> > Some other languages have stronger guarantees about their array
> dimensions accesses being in range. But this being
2017 Feb 13
2
RFC: Representing unions in TBAA
>
>
> I don't think this fully solves the problem -- you'll also need to fix
> getMostGenericTBAA. That is, even if you implement the above scheme,
> say you started out with:
>
> union U {
> int i;
> float f;
> };
>
> float f(union U *u, int *ii, float *ff, bool c) {
> if (c) {
> *ii = 10;
> *ff = 10.0;
> } else {
>
2007 Mar 22
0
[LLVMdev] a question about constant fold for fdiv
On Thu, 2007-03-22 at 15:50 -0700, leo han wrote:
> Hello, I have a question about the constant folding for fdiv instructions.
> For the instruction "fdiv double 0.0, 0.0", the folded result is inf. I
> think this should be nan. Can anyone tell me why it is not nan?
I think the specification says that it is "undefined" so any value will
do. inf is just as undefined
2007 Oct 06
1
[LLVMdev] memcpy(), memmove(), and memset() with zero length
If I copy or set zero bytes with memcpy(), memmove(), or memset(), can
the <dest> and <src> arguments be null? Can they be invalid pointers?
Regards,
Jon
2007 Mar 22
3
[LLVMdev] a question about constant fold for fdiv
Hello, I have a question about the constant folding for fdiv instructions.
For the instruction "fdiv double 0.0, 0.0", the folded result is inf. I
think this should be nan. Can anyone tell me why it is not nan?
Thanks.
Leo
_________________________________________________________________
Exercise your brain! Try Flexicon.
2007 Mar 22
2
[LLVMdev] a question about constant fold for fdiv
...d be nan. Can anyone tell me why it is not nan?
>>>>
>>>
>>> I think the specification says that it is "undefined" so any value will
>>> do. inf is just as undefined as nan.
>>>
>>> Reid.
>>
>> In IEEE Std 754-1985, subclause 7.2- Division by Zero, it says:
>>
>> /"If the divisor is zero and the dividend is a finite nonzero number,
>> then the division by zero shall be signaled. The result, when no trap
>> occurs, shall be a correctly signed (infinity symbol)(6.3)."
>>
>>...
2018 Nov 14
2
[PATCH v2] test-data: Allow tests to be run when Btrfs is not available.
v2:
- Moved the btrfs available test into the subclause where it is used.
Note I got tired of fighting emacs indentation mode and I pushed a
whitespace only patch which fixes the indentation to be 4 spaces
instead of 2 spaces:
https://github.com/libguestfs/libguestfs/commit/df54c75d4c53ed580e5269306e11e0758d169452
This v2 patch requires that one....
2017 Jul 20
2
Which assumptions do llvm.memcpy/memmove/memset.* make when the count is 0?
Hi all,
when I call the llvm.memcpy/memmove/memset.* intrinsics, typically I
have to pass in valid (non-dangling, non-NULL pointers) of the given
alignment. However, to what extent to these rules apply when the count
is 0? Concretely (for any variant of the three aforementioned
intrinsics): Is it UB to call them on a dangling pointer when count is
0? On a pointer of less than the given
2019 Oct 08
2
PR43374 - when should comparing NaN values raise a floating point exception?
* Sanjay Patel via llvm-dev <llvm-dev at lists.llvm.org> [2019-10-01 09:44:54 -0400]:
> Let's change the example to eliminate suspects:
> #include <math.h>
> int is_nan(float x) {
> /*
> The following subclauses provide macros that are quiet (non
> floating-point exception raising)
> versions of the relational operators, and other comparison macros
> that facilitate writing
> efficient code that accounts for NaNs without suffering the
> ‘‘invalid’’ floating-point exception.
>...
2017 Feb 14
2
RFC: Representing unions in TBAA
...t;>> "necessary for a reasonable interpretation" or something.
>>>>
>>>> Because we would be *functionally correct* by the standard by
>>>> destroying the program if you ever read the member you didn't set :)
>>>>
>>> C11 subclause 6.5.2.3 paragraph 3, has in footnote 95:
>>> If the member used to read the contents of a union object is not the
>>> same as the member last used to store a value in the object, the
>>> appropriate part of the object representation of the value is reinterpreted
>>&...