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Add "algebraic" versions of the fast-math intrinsics

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This commit is contained in:
Ben Kimock 2024-02-06 14:32:00 -05:00
parent c9a7db6e20
commit cc73b71e8e
12 changed files with 226 additions and 14 deletions
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25
compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
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@ -418,7 +418,11 @@ extern "C" LLVMAttributeRef LLVMRustCreateMemoryEffectsAttr(LLVMContextRef C,
}
}
// Enable a fast-math flag
// Enable all fast-math flags, including those which will cause floating-point operations
// to return poison for some well-defined inputs. This function can only be used to build
// unsafe Rust intrinsics. That unsafety does permit additional optimizations, but at the
// time of writing, their value is not well-understood relative to those enabled by
// LLVMRustSetAlgebraicMath.
//
// https://llvm.org/docs/LangRef.html#fast-math-flags
extern "C" void LLVMRustSetFastMath(LLVMValueRef V) {
@ -427,6 +431,25 @@ extern "C" void LLVMRustSetFastMath(LLVMValueRef V) {
}
}
// Enable fast-math flags which permit algebraic transformations that are not allowed by
// IEEE floating point. For example:
// a + (b + c) = (a + b) + c
// and
// a / b = a * (1 / b)
// Note that this does NOT enable any flags which can cause a floating-point operation on
// well-defined inputs to return poison, and therefore this function can be used to build
// safe Rust intrinsics (such as fadd_algebraic).
//
// https://llvm.org/docs/LangRef.html#fast-math-flags
extern "C" void LLVMRustSetAlgebraicMath(LLVMValueRef V) {
if (auto I = dyn_cast<Instruction>(unwrap<Value>(V))) {
I->setHasAllowReassoc(true);
I->setHasAllowContract(true);
I->setHasAllowReciprocal(true);
I->setHasNoSignedZeros(true);
}
}
extern "C" LLVMValueRef
LLVMRustBuildAtomicLoad(LLVMBuilderRef B, LLVMTypeRef Ty, LLVMValueRef Source,
const char *Name, LLVMAtomicOrdering Order) {