David Stenberg 97861981cc [LiveDebugVariables] Fix a DBG_VALUE reordering issue (#111124) ...

LDV could reorder reinserted fragment and non-fragment debug values for
the same variable (compared to the input order), potentially resulting
in stale values being presented.

For example, before:

  DBG_VALUE 1001, $noreg, !13, !DIExpression(DW_OP_LLVM_fragment, 0, 16)
  DBG_VALUE 1002, $noreg, !13, !DIExpression(DW_OP_LLVM_fragment, 16, 16)
  DBG_VALUE %0, $noreg, !13, !DIExpression()

After (without this patch):

  DBG_VALUE %stack.0, 0, !13, !DIExpression()
  DBG_VALUE 1002, $noreg, !13, !DIExpression(DW_OP_LLVM_fragment, 16, 16)
  DBG_VALUE 1001, $noreg, !13, !DIExpression(DW_OP_LLVM_fragment, 0, 16)

It would also reorder DBG_VALUEs for different variables. Although that
does not matter for the debug information output, it resulted in some
noise in before/after pass diffs.

This should hopefully align so that instruction referencing and
DBG_VALUE emit debug instructions in the same order (see the
sdag-salvage-add.ll change).

2024-10-15 11:36:24 +02:00

74 KiB

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