LLVM incorrectly assumes `long double` is the same type as `_Float128` on ppc64le

[programmerjake]

/build/source/llvm/llvm/lib/Analysis/ConstantFolding.cpp:2129:34: error: invalid conversion from '_Float128 (*)(_Float128) noexcept' to 'long double (*)(long double)' [-fpermissive]
 2129 |         return ConstantFoldFP128(logf128, Op->getValueAPF(), Ty);
      |                                  ^~~~~~~
      |                                  |
      |                                  _Float128 (*)(_Float128) noexcept
/build/source/llvm/llvm/lib/Analysis/ConstantFolding.cpp:1787:43: note:   initializing argument 1 of 'llvm::Constant* {anonymous}::ConstantFoldFP128(long double (*)(long double), const llvm::APFloat&, llvm::Type*)'
 1787 | Constant *ConstantFoldFP128(long double (*NativeFP)(long double),
      |                             ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

ConstantFoldFP128's definition:

llvm-project/llvm/lib/Analysis/ConstantFolding.cpp

Lines 1786 to 1798 in 599f8e1

	#if defined(HAS_IEE754_FLOAT128) && defined(HAS_LOGF128)
	Constant *ConstantFoldFP128(long double (*NativeFP)(long double),
	const APFloat &V, Type *Ty) {
	llvm_fenv_clearexcept();
	float128 Result = NativeFP(V.convertToQuad());
	if (llvm_fenv_testexcept()) {
	llvm_fenv_clearexcept();
	return nullptr;
	}
	return GetConstantFoldFPValue128(Result, Ty);
	}
	#endif

Where it's called with mismatched types:

llvm-project/llvm/lib/Analysis/ConstantFolding.cpp

Line 2129 in 599f8e1

return ConstantFoldFP128(logf128, Op->getValueAPF(), Ty);

[programmerjake]

The broken code was added in #94944 by @MDevereau

[llvmbot]

@llvm/issue-subscribers-backend-powerpc

Author: Jacob Lifshay (programmerjake)

``` /build/source/llvm/llvm/lib/Analysis/ConstantFolding.cpp:2129:34: error: invalid conversion from '_Float128 (*)(_Float128) noexcept' to 'long double (*)(long double)' [-fpermissive] 2129 | return ConstantFoldFP128(logf128, Op->getValueAPF(), Ty); | ^~~~~~~ | | | _Float128 (*)(_Float128) noexcept /build/source/llvm/llvm/lib/Analysis/ConstantFolding.cpp:1787:43: note: initializing argument 1 of 'llvm::Constant* {anonymous}::ConstantFoldFP128(long double (*)(long double), const llvm::APFloat&, llvm::Type*)' 1787 | Constant *ConstantFoldFP128(long double (*NativeFP)(long double), | ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~ ```

ConstantFoldFP128's definition:

llvm-project/llvm/lib/Analysis/ConstantFolding.cpp

Lines 1786 to 1798 in 599f8e1

	#if defined(HAS_IEE754_FLOAT128) && defined(HAS_LOGF128)
	Constant *ConstantFoldFP128(long double (*NativeFP)(long double),
	const APFloat &V, Type *Ty) {
	llvm_fenv_clearexcept();
	float128 Result = NativeFP(V.convertToQuad());
	if (llvm_fenv_testexcept()) {
	llvm_fenv_clearexcept();
	return nullptr;
	}
	return GetConstantFoldFPValue128(Result, Ty);
	}
	#endif

Where it's called with mismatched types:

llvm-project/llvm/lib/Analysis/ConstantFolding.cpp

Line 2129 in 599f8e1

return ConstantFoldFP128(logf128, Op->getValueAPF(), Ty);