[LLVMdev] More careful treatment of floating point exceptions

[Sanjay Patel]

Hi Sergey -

Does this solve part of the problem?
http://llvm.org/viewvc/llvm-project?view=revision&revision=215222

On Fri, Sep 19, 2014 at 9:12 AM, Sergey Dmitrouk <sdmitrouk at accesssoftek.com
> wrote:

> Hi,
>
> I'd like to make code emitted by LLVM that includes floating point
> operations which raise FP exceptions behave closer to what is defined by
> IEEE754 standard.  I'm not going to "fix everything", just incorrect
> behaviour I faced so far.
>
> Most of troubles regarding FP exceptions are caused by optimizations, so
> there should be a flag to disable/block them if one wants to get better
> code in a sense of its IEEE754 conformance.  I couldn't find an existing
> flag for this and would like to introduce one.  I guess it should be
> added to llvm::TargetOptions (e.g. "IEEE754FPE"), then -std=c99 or
> separate option could enable it from front-end (Clang in this case).
>
> I'm doing this for ARM platform and the flag should be reachable from
> all these places in LLVM:
>
>  - lib/Analysis/ValueTracking.cpp
>  - lib/CodeGen/SelectionDAG/SelectionDAG.cpp
>  - lib/IR/ConstantFold.cpp
>  - lib/Target/ARM/ARMFastISel.cpp
>  - lib/Target/ARM/ARMISelLowering.cpp
>  - lib/Target/ARM/ARMInstrVFP.td (through predicates)
>  - lib/Target/ARM/ARMRegisterInfo.td (through predicates)
>
> and in Clang:
>
>  - lib/AST/ExprConstant.cpp
>
> Did I get it right and there is no such flag so far?  Does what I'm
> suggesting sounds reasonable?
>
> Thanks,
> Sergey
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