AMDGPU SALU pseudos should not have side effects

[jayfoad]

The following pseudos do not have an explicit hasSideEffects = 0 in the *.td files, so the MCInstrs are marked as MCID::UnmodeledSideEffects:

S_ADD_CO_PSEUDO
S_MUL_I64_I32_PSEUDO
S_MUL_U64_U32_PSEUDO
S_SUB_CO_PSEUDO
S_UADDO_PSEUDO
S_USUBO_PSEUDO

These are all regular ALU operations without side effects.

[llvmbot]

@llvm/issue-subscribers-backend-amdgpu

Author: Jay Foad (jayfoad)

The following pseudos do not have an explicit `hasSideEffects = 0` in the *.td files, so the MCInstrs are marked as `MCID::UnmodeledSideEffects`: ``` S_ADD_CO_PSEUDO S_MUL_I64_I32_PSEUDO S_MUL_U64_U32_PSEUDO S_SUB_CO_PSEUDO S_UADDO_PSEUDO S_USUBO_PSEUDO ``` These are all regular ALU operations without side effects.