Register allocation may spill virtual registers to the stack, which can
increase alignment requirements of the stack frame. If the the function
did not require stack realignment before register allocation, the
registers required to do so may not be reserved/available. This results
in a stack frame that requires realignment but can not be realigned.
Instead, only increase the alignment of the stack if we are still able
to realign.
The register SpillAlignment will be ignored if we can't realign, and the
backend will be responsible for emitting the correct unaligned loads and
stores. This seems to be the assumed behaviour already, e.g.
ARMBaseInstrInfo::storeRegToStackSlot and X86InstrInfo::storeRegToStackSlot
are both `canRealignStack` aware.
Differential Revision: https://reviews.llvm.org/D103602
We create MMO's for the VLDn/VSTn intrinsics in ARMTargetLowering::
getTgtMemIntrinsic, but they do not currently make it ll the way through
ISel. This changes that in the various places it needs changing, making
sure that the MMO is propagate through to the final instruction. This
can help in scheduling, not treating the VLD2/VST2 as a scheduling
barrier.
Differential Revision: https://reviews.llvm.org/D101096
https://bugs.llvm.org/show_bug.cgi?id=48232
When PrologEpilogInserter writes callee-saved registers to the stack, LR is not reloaded but is instead loaded directly into PC.
This was not taken into account when determining if each callee-saved register was liveout for the block.
When frame elimination inserts virtual registers, and the register scavenger tries to scavenge LR, it considers it liveout and tries to spill again.
However there is no emergency spill slot to use, and it fails with an error:
fatal error: error in backend: Error while trying to spill LR from class GPR: Cannot scavenge register without an emergency spill slot!
This patch pervents any callee-saved registers which are not reloaded (including LR) from being marked liveout.
They are therefore available to scavenge without requiring an extra spill.
This adds Post inc variants of the VLD2/4 and VST2/4 instructions in
MVE. It uses the same mechanism/nodes as Neon, transforming the
intrinsic+add pair into a ARMISD::VLD2_UPD, which gets selected to a
post-inc instruction. The code to do that is mostly taken from the
existing Neon code, but simplified as less variants are needed.
It also fills in some getTgtMemIntrinsic for the arm.mve.vld2/4
instrinsics, which allow the nodes to have MMO's, calculated as the full
length to the memory being loaded/stored.
Differential Revision: https://reviews.llvm.org/D71194
Tomas Matheson