john.brawn added inline comments.
================
Comment at: lib/Driver/ToolChains/Clang.cpp:2452
+ if (!HonorInfs && !HonorNans && !MathErrno && AssociativeMath &&
+ ReciprocalMath && !SignedZeros && !TrappingMath && FpContract == "fast")
+ CmdArgs.push_back("-ffast-math");
----------------
rengolin wrote:
> rengolin wrote:
> > This is technically correct, but users will be confused if they choose
> > `-ffast-math -ffp-contract=on` and not see `-ffast-math` coming out on the
> > other side.
> >
> > Also, `fp-contract=on` doesn't preclude `-ffast-math` for the languages
> > that support it, so I wouldn't add `FpContract` to this list at all.
> I've been thinking a bit more about this, and I started wondering, why do we
> even need to pass `-ffast-math` down?
>
> If all the others are already being passed, shouldn't this flag be redundant?
>
> Finally, we could possibly add instead `&& FpContract != "off"`. Would that
> be better?
As the comment above says, -ffast-math enables the __FAST_MATH__ macro.
As to FpContract, going back and checking gcc setting -ffp-contract has no
effect on whether __FAST_MATH__ is defined so I think just not checking
FpContract here is correct.
================
Comment at: lib/Driver/ToolChains/Clang.cpp:2347
+ // Validate and pass through -fp-contract option.
+ case options::OPT_ffp_contract: {
+ StringRef Val = A->getValue();
----------------
rengolin wrote:
> Also, when `-ffast-math` is selected, and `-ffp-contract=on`, we should
> actually change it to `fast`, no?
Do you mean "clang -ffp-contract=on -ffast-math should set fp-contract to fast"
or "clang -ffast-math -ffp-contract=on should set fp-contract to fast"? The
first is already done by the -ffast-math handling below, and I think the second
is a bad idea because it violates the principle that later command-line options
have priority over earlier ones.
================
Comment at: lib/Driver/ToolChains/Clang.cpp:2356
+ }
+
+ case options::OPT_ffinite_math_only:
----------------
rengolin wrote:
> Missing break?
Whoops, will fix.
Repository:
rL LLVM
https://reviews.llvm.org/D30582
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