[ImplicitNullChecks] Hoist trivial depdendencies if possible
When trying to convert a loading instruction into a FAULTING_LOAD, we
sometimes face code like this:
if %R10 is not null:
%R9<def> = MOV32ri Immediate
%R9<def, tied> = AND32rm %R9, 0x20(%R10)
else:
goto TRAP
In these cases we would like to use the AND32rm instruction as the
faulting operation by hoisting the "depedency" def-ing %R9 also above
the control flow, transforming the program into:
%R9<def> = MOV32ri Immediate
%R9<def, tied> = FAULTING_LOAD_OP(AND32rm %R9, 0x20(%R10), FailPath: TRAP)
This change teaches ImplicitNullChecks to do the above, when safe.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273501 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed