In order to set breakpoints on labels and list source code around
labels, we need collect debug information for labels, i.e., label
name, the function label belong, line number in the file, and the
address label located. In order to keep these information in LLVM
IR and to allow backend to generate debug information correctly.
We create a new kind of metadata for labels, DILabel. The format
of DILabel is
!DILabel(scope: !1, name: "foo", file: !2, line: 3)
We hope to keep debug information as much as possible even the
code is optimized. So, we create a new kind of intrinsic for label
metadata to avoid the metadata is eliminated with basic block.
The intrinsic will keep existing if we keep it from optimized out.
The format of the intrinsic is
llvm.dbg.label(metadata !1)
It has only one argument, that is the DILabel metadata. The
intrinsic will follow the label immediately. Backend could get the
label metadata through the intrinsic's parameter.
We also create DIBuilder API for labels to be used by Frontend.
Frontend could use createLabel() to allocate DILabel objects, and use
insertLabel() to insert llvm.dbg.label intrinsic in LLVM IR.
Differential Revision: https://reviews.llvm.org/D45024
Patch by Hsiangkai Wang.
llvm-svn: 331841
Summary:
When building the selection DAG at ISel all PHI nodes are
selected and lowered to Machine Instruction PHI nodes before
we start to create any SDNodes. So there are no SDNodes for
values produced by the PHI nodes.
In the past when selecting a dbg.value intrinsic that uses
the value produced by a PHI node we have been handling such
dbg.value intrinsics as "dangling debug info". I.e. we have
not created a SDDbgValue node directly, because there is
no existing SDNode for the PHI result, instead we deferred
the creationg of a SDDbgValue until we found the first use
of the PHI result.
The old solution had a couple of flaws. The position of the
selected DBG_VALUE instruction would end up quite late in a
basic block, and for example not directly after the PHI node
as in the LLVM IR input. And in case there were no use at all
in the basic block the dbg.value could be dropped completely.
This patch introduces a new VREG kind of SDDbgValue nodes.
It is similar to a SDNODE kind of node, but it refers directly
to a virtual register and not a SDNode. When we do selection
for a dbg.value that is using the result of a PHI node we
can do a lookup of the virtual register directly (as it already
is determined for the PHI node) and create a SDDbgValue node
immediately instead of delaying the selection until we find a
use.
This should fix a problem with losing debug info at ISel
as seen in PR37234 (https://bugs.llvm.org/show_bug.cgi?id=37234).
It does not resolve PR37234 completely, because the debug info
is dropped later on in the BranchFolder (see D46184).
Reviewers: #debug-info, aprantl
Reviewed By: #debug-info, aprantl
Subscribers: rnk, gbedwell, aprantl, JDevlieghere, llvm-commits
Differential Revision: https://reviews.llvm.org/D46129
llvm-svn: 331182
Shiva Chen