[smitop]

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).

[simonbyrne]

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?

[diamondlovesyou]

(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.

[gmueckl]

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.

[StefanKarpinski]

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.