[PATCH] D51678: ARM: fix Thumb2 CodeGen for ldrex with folded frame-index

[Tim Northover via Phabricator via llvm-commits]

t.p.northover created this revision.
t.p.northover added a reviewer: eli.friedman.
Herald added subscribers: chrib, hiraditya, kristof.beyls, mcrosier.
Herald added a reviewer: javed.absar.

As reported in https://llvm.org/PR38828, Thumb2 ldrex instructions accessing local variables are not being handled correctly. In release builds this results in bad code, in debug builds an assertion.

The issue is that the t2LDREX and t2STREX instructions are marked with `AddrModeNone`, but rewriteT2FrameIndex relies on knowing the addressing-mode so that it can fold a stack offset into the instruction. This patch adds a new addressing-mode to handle the situation and applies it to the relevant instructions.

Neither the byte/half/dword forms, nor any ARM variant is affected because they do not allow an offset to the base register.


Repository:
  rL LLVM

https://reviews.llvm.org/D51678

Files:
  llvm/lib/Target/ARM/ARMInstrFormats.td
  llvm/lib/Target/ARM/ARMInstrThumb2.td
  llvm/lib/Target/ARM/MCTargetDesc/ARMBaseInfo.h
  llvm/lib/Target/ARM/Thumb2InstrInfo.cpp
  llvm/test/CodeGen/ARM/ldstrex.ll

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