llvm-project

f5973675 - [flang][HLFIR] add skip_rebox option to hlfir.declare (#162305)

[flang][HLFIR] add skip_rebox option to hlfir.declare (#162305) hlfir.declare with a fir.box input always lead to a fir.rebox being created to ensure the lower bounds and attributes are set correctly in the local descriptor for the entity. This is really needed for hlfir.declare using fir.box function argument that do not come with any guarantees with regards to the lower bounds. Sometimes however, this fir.rebox just adds a lot of noise in the SSA chain, especially at the LLVM level and it is known that the input descriptor is already correct. I am making this patch in the context of OpenACC where I want to remap the variables inside the compute region, creating a fir.rebox on the way. This fir.rebox cannot be optimized away by FIR because of the OpenACC ops in the SSA chain. This patch adds a flag to indicate the the fir.box is known to have the correct lower bounds and attributes so that it can have a simpler code generation to FIR.