Duncan P. N. Exon Smith c89369a941 Linker: Drop function pointers for overridden subprograms ... Instead of dropping subprograms that have been overridden, just set their function pointers to `nullptr`. This is a minor adjustment to the stop-gap fix for PR21910 committed in r224487, and fixes the crasher from PR22792. The problem that r224487 put a band-aid on: how do we find the canonical subprogram for a `Function`? Since the backend currently relies on `DebugInfoFinder` (which does a naive in-order traversal of compile units and picks the first subprogram) for this, r224487 tried dropping non-canonical subprograms. Dropping subprograms fails because the backend *also* builds up a map from subprogram to compile unit (`DwarfDebug::SPMap`) based on the subprogram lists. A missing subprogram causes segfaults later when an inlined reference (such as in this testcase) is created. Instead, just drop the `Function` pointer to `nullptr`, which nicely mirrors what happens when an already-inlined `Function` is optimized out. We can't really be sure that it's the same definition anyway, as the testcase demonstrates. This still isn't completely satisfactory. Two flaws at least that I can think of: - I still haven't found a straightforward way to make this symmetric in the IR. (Interestingly, the DWARF output is already symmetric, and I've tested for that to be sure we don't regress.) - Using `DebugInfoFinder` to find the canonical subprogram for a function is kind of crazy. We should just attach metadata to the function, like this: define weak i32 @foo(i32, i32) !dbg !MDSubprogram(...) { git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233164 91177308-0d34-0410-b5e6-96231b3b80d8		2015-03-25 02:26:32 +00:00
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CMakeLists.txt
LinkModules.cpp	Linker: Drop function pointers for overridden subprograms	2015-03-25 02:26:32 +00:00
LLVMBuild.txt
Makefile