• Ilya (6/6) Dec 30 2015 Hi,
• Johan Engelen (6/10) Dec 31 2015 Clang implements the pragma `#pragma STDC FP_CONTRACT` (you can
• Johan Engelen (7/8) Dec 31 2015 I take that back. It is simple to implement the pragma itself,

Ilya <ilyayaroshenko gmail.com> writes:

Hi,

Can fp-constract flag be added to LDC to allow auto fusion of 
mull/add operations?

Is it possible to make `fp-constract` a function attribute?

Thanks,
Ilya

Johan Engelen <j j.nl> writes:

On Thursday, 31 December 2015 at 04:32:27 UTC, Ilya wrote:
 Hi,

 Can fp-constract flag be added to LDC to allow auto fusion of 
 mull/add operations?

 Is it possible to make `fp-constract` a function attribute?

Clang implements the pragma `#pragma STDC FP_CONTRACT` (you can 
enable it per compound statement). I think it's good to do the 
same. This should be relatively simple to implement.

See: 
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/fp-contract-pragma.cpp?view=markup

Johan Engelen <j j.nl> writes:

On Thursday, 31 December 2015 at 13:07:47 UTC, Johan Engelen 
wrote:
  This should be relatively simple to implement.

I take that back. It is simple to implement the pragma itself, 
but actually fusing ops (in the frontend) will be some more work 
/ requires deeper knowledge of LDC.
For a future implementer: you may want to have a look at clang's 
"tryEmitFMulAdd()" in lib/CodeGen/CGExprScalar.cpp.