Somewhat unnoticed in the original implementation of discriminators, but
it could cause instructions to end up in new, small,
DW_TAG_lexical_blocks due to the use of DILexicalBlock to track
discriminator changes.
Instead, use DILexicalBlockFile which we already use to track file
changes without introducing new scopes, so it works well to track
discriminator changes in the same way.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216239 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
This prevents the discriminator generation pass from triggering if
the DWARF version being used in the module is prior to 4.
Reviewers: echristo, dblaikie
CC: llvm-commits
Differential Revision: http://reviews.llvm.org/D3413
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206507 91177308-0d34-0410-b5e6-96231b3b80d8
DWARF discriminators are used to distinguish multiple control flow paths
on the same source location. When this happens, instructions across
basic block boundaries will share the same debug location.
This pass detects this situation and creates a new lexical scope to one
of the two instructions. This lexical scope is a child scope of the
original and contains a new discriminator value. This discriminator is
then picked up from MCObjectStreamer::EmitDwarfLocDirective to be
written on the object file.
This fixes http://llvm.org/bugs/show_bug.cgi?id=18270.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202752 91177308-0d34-0410-b5e6-96231b3b80d8
