[PATCH] D75755: [AArch64][Fix] LdSt optimization generate premature stack-popping

[Diogo N. Sampaio via Phabricator via llvm-commits]

dnsampaio created this revision.
dnsampaio added reviewers: fhahn, foad, thegameg, eli.friedman.
Herald added subscribers: llvm-commits, danielkiss, hiraditya, kristof.beyls.
Herald added a project: LLVM.

When moving add and sub to memory operand instructions,
aarch64-ldst-opt would prematurally pop the stack pointer,
before memory instructions that do access the stack using
indirect loads.
e.g.

  int foo(int offset){
      int local[4] = {0};
      return local[offset];
  }

would generate:

  sub     sp, sp, #16            ; Push the stack
  mov     x8, sp                 ; Save stack in register
  stp     xzr, xzr, [sp], #16    ; Zero initialize stack, and post-increment, making it invalid
  ------ If an exception goes here, the stack value might be corrupted
  ldr     w0, [x8, w0, sxtw #2]  ; Access correct position, but it is not guarded by SP


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D75755

Files:
  llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
  llvm/test/CodeGen/AArch64/aarch64-ldst-no-premature-sp-pop.mir
  llvm/test/CodeGen/AArch64/arm64-nvcast.ll

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