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[Reapplies r297971 and punting on finding a better API for findDbgValues()] This patch improves debug info quality in InstCombine by looking at values that are about to be deleted, checking whether there are any dbg.value instrinsics referring to them, and potentially encoding the semantics of the deleted instruction into the dbg.value's DIExpression. In the example in the testcase (which was extracted from XNU) there is a sequence of %4 = load %struct.entry*, %struct.entry** %next2, align 8, !dbg !41 %5 = bitcast %struct.entry* %4 to i8*, !dbg !42 %add.ptr4 = getelementptr inbounds i8, i8* %5, i64 -8, !dbg !43 %6 = bitcast i8* %add.ptr4 to %struct.entry*, !dbg !44 call void @llvm.dbg.value(metadata %struct.entry* %6, i64 0, metadata !20, metadata !21), !dbg 34 When these instructions are eliminated by instcombine one after another, we can still salvage the otherwise dead debug info: - Bitcasts have no effect, so have the dbg.value point to operand(0) - Loads can be expressed via a DW_OP_deref - Constant gep instructions can be replaced by DWARF expression arithmetic The API introduced by this patch is not specific to instcombine and can be useful in other places, too. rdar://problem/30725338 Differential Revision: https://reviews.llvm.org/D30919 llvm-svn: 297994 |
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| Analysis | ||
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| BugPoint | ||
| CodeGen | ||
| DebugInfo | ||
| Examples | ||
| ExecutionEngine | ||
| Feature | ||
| FileCheck | ||
| Instrumentation | ||
| Integer | ||
| JitListener | ||
| LibDriver | ||
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| MC | ||
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| tools | ||
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| Unit | ||
| Verifier | ||
| YAMLParser | ||
| .clang-format | ||
| CMakeLists.txt | ||
| lit.cfg | ||
| lit.site.cfg.in | ||
| TestRunner.sh | ||