[LLVMdev] Helping the optimizer along (__assume)

Duncan Sands baldrick at free.fr
Thu Oct 23 05:30:58 PDT 2008


>  * Mark the instructions used for assumptions explicitely, so they won't get
>    modified, i.e.:
> 		%cond = icmp ne i32 %p, 0
> 		call void @llvm.assume( i1 %cond )

gcc uses the equivalent of:

	%p2 = call @llvm.assume(i32 %p, "ne", i32 0)

with %p2 being used for %p wherever this assumption
if valid (for example in the "true" branch of an
"if (%p != 0) {...}").



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