[llvm-commits] Please review: FMA3 instructions set

[Demikhovsky, Elena]

By default, FMA should be switched on. The "#pragma FP_COTRACT off "deprecates FMA. But there is no direct link in the LLVM sources between the pragma and code generation options.

- Elena

-----Original Message-----
From: Anton Korobeynikov [mailto:anton at korobeynikov.info] 
Sent: Tuesday, May 22, 2012 19:53
To: Stephen Canon
Cc: Demikhovsky, Elena; llvm-commits at cs.uiuc.edu
Subject: Re: [llvm-commits] Please review: FMA3 instructions set

> Do I understand correctly that this patch lowers fadd + fmul to fma by default?  We want it to be easy for LLVM to generate fma when it is beneficial to performance, but we can't simply naively lower to it everywhere and still conform to language semantics.  Someone else can speak to what policy should be here, but at the very least we will need to have an option to block fma formation.
One can check how fma is implemented on ARM. In general - stuff should be guarded by NoExcessPrecision flag or something like this

--
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University
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