thopre marked 2 inline comments as done.
thopre added inline comments.
================
Comment at: clang/lib/CodeGen/CGBuiltin.cpp:2995
+ Builder.getDefaultConstrainedExcept() == fp::ebIgnore ||
+ !Ty->isIEEE()) {
+ V = Builder.CreateFCmpUNO(V, V, "cmp");
----------------
I'm not too sure if that's enough to check isIEEE here. x86 extended precision
behaves a bit different to IEEE single and double precision, esp. wrt. infinite
and NaN. I've decided to ignore NaN values that are deprecated since the 8087.
================
Comment at: clang/lib/CodeGen/CGBuiltin.cpp:3001
+ // NaN has all exp bits set and a non zero significand. Therefore:
+ // isnan(V) == ((abs(V) & exp mask) - exp mask < 0)
+ unsigned bitsize = Ty->getScalarSizeInBits();
----------------
mibintc wrote:
> Are you using a reference (e.g. existing implementation) for this rewrite, or
> is this invention? If a reference can you please tell me what it is. The
> expression you have written here doesn't match the codegen below. I don't see
> the comparison to zero. Can you provide full parenthesization--the compare to
> zero is lower than subtract?
I've noticed glibc isnan implementation does not trigger a trap so I've looked
at the assembly it generates for the float case. This is the generalized
version for double and long double as well.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D95948/new/
https://reviews.llvm.org/D95948
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