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).
97861981cc