[all-commits] [llvm/llvm-project] 6b2fd7: [MIPS] Use generic isBlockOnlyReachableByFallthrou...

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6b2fd7aed66d592738f26c76caa8fff95e168598
      https://github.com/llvm/llvm-project/commit/6b2fd7aed66d592738f26c76caa8fff95e168598
  Author: Fangrui Song <i at maskray.me>
  Date:   2024-02-06 (Tue, 06 Feb 2024)

  Changed paths:
    M llvm/lib/Target/Mips/MipsAsmPrinter.cpp
    M llvm/lib/Target/Mips/MipsAsmPrinter.h
    M llvm/test/CodeGen/Mips/Fast-ISel/pr40325.ll
    M llvm/test/CodeGen/Mips/GlobalISel/llvm-ir/jump_table_and_brjt.ll
    M llvm/test/CodeGen/Mips/compactbranches/unsafe-in-forbidden-slot.ll
    M llvm/test/CodeGen/Mips/indirect-jump-hazard/jumptables.ll
    M llvm/test/CodeGen/Mips/jump-table-mul.ll
    M llvm/test/CodeGen/Mips/pseudo-jump-fill.ll

  Log Message:
  -----------
  [MIPS] Use generic isBlockOnlyReachableByFallthrough (#80799)

FastISel may create a redundant BGTZ terminal which fallthroughes.
```
  BGTZ %2:gpr32, %bb.1, implicit-def $at

bb.1.bb1:
; predecessors: %bb.0
```

The `!I->isBarrier()` check in
MipsAsmPrinter::isBlockOnlyReachableByFallthrough
will incorrectly not print a label, leading to a `Undefined temporary
symbol `
error when we try assembling the output assembly file. See the updated
`Fast-ISel/pr40325.ll` and
https://github.com/rust-lang/rust/issues/108835

In addition, the `SwitchInst` condition is too conservative and prints
many unneeded labels (see the updated tests).

Just use the generic isBlockOnlyReachableByFallthrough, updated by
commit 1995b9fead62f2f6c0ad217bd00ce3184f741fdb for SPARC, which also
handles MIPS.