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The LLVM IR is more expressive than clang is for expressing fast-math: it supports making an operation use fast-math optimization on a per operation basis (https://llvm.org/docs/LangRef.html#fastmath).

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Do you know what happens when you have ops with different flags? e.g. if you have (a + b) + c, where one + allows reassoc but one doesn't?

(a+b)+c has two ops in LLVM: addition is a binop, meaning it has two "arguments", thus (a+b) and adding "c" are separate instructions. You can't directly add three or more values.

I believe the parent wants to know how a sequence of IR instructions with alternating modes is translated to the target.

My guess would be that explicit state state changes show up in the generated machine code.

Right, the question becomes: if you have `(a + b) + c` and one of the `+` operations allows re-association but the other one doesn't, then what happens? The problem being that associativity is a property that only makes sense for an entire tree of associable operations, not individual ones.

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