mgehre-amd marked an inline comment as done.
mgehre-amd added inline comments.
================
Comment at: clang/include/clang/Basic/DiagnosticSemaKinds.td:8422
+def err_int_to_float_bit_int_max_size : Error<
+ "cannot convert '_BitInt' operands of more than %0 bits to floating point">;
----------------
erichkeane wrote:
> Can you explain the issue here? This is supposed to be well-defined behavior.
I saw `Assertion LC != RTLIB::UNKNOWN_LIBCALL && "Don't know how to expand this
SINT_TO_FP!"' failed.` in the backend. I think we would need to add library
calls for floating to bitint (and vice versa) to the bitint library to enable
that.
================
Comment at: clang/lib/Lex/LiteralSupport.cpp:1232
+ if (llvm::isPowerOf2_32(radix)) {
+ unsigned BitsPerDigit = llvm::Log2(radix);
----------------
erichkeane wrote:
> Can you explain what is going on here? This isn't at all obvious to me.
When I adapted the test case clang/test/Lexer/bitint-constants.c
https://reviews.llvm.org/D122234#change-GjEFAAe2jzfe to test literals with
2097152 hex digits, clang spend minutes in the code below to try to turn that
literal into a ApInt of 8388608 bits.
That is because the code below does a generic `Val *= Radix` and `Val +=
Digit`. The `Val *= Radix` is very slow on a ApInt with 8388608 bits, and it's
also not needed when
we know that `Radix` is a power of two. Then one can just copy the bits from
each Digit into the right position in Val.
If the integer literals can just be 128 bits or something, it doesn't matter,
but now we need to support really big integer literals with having increased
the limit on _BitInt width.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D122234/new/
https://reviews.llvm.org/D122234
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