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Summary: This changes the ParamLoadedValue pair which the describeLoadedValue() hook returns so that MachineOperand objects are returned instead of pointers. When describing call site values we may need to describe operands which are not part of the instruction. One such example is zero-materializing XORs on x86, which I have implemented support for in a child revision. Instead of having to return a pointer to an operand stored somewhere outside the instruction, start returning objects directly instead, as that simplifies the code. The MachineOperand class only holds POD members, and on x86-64 it is 32 bytes large. That combined with copy elision means that the overhead of returning a machine operand object from the hook does not become very large. I benchmarked this on a 8-thread i7-8650U machine with 32 GB RAM. The benchmark consisted of building a clang 8.0 binary configured with: -DCMAKE_BUILD_TYPE=RelWithDebInfo \ -DLLVM_TARGETS_TO_BUILD=X86 \ -DLLVM_USE_SANITIZER=Address \ -DCMAKE_CXX_FLAGS="-Xclang -femit-debug-entry-values -stdlib=libc++" The average wall clock time increased by 4 seconds, from 62:05 to 62:09, which is an 0.1% increase. Reviewers: aprantl, vsk, djtodoro, NikolaPrica Reviewed By: vsk Subscribers: hiraditya, ychen, llvm-commits Tags: #debug-info, #llvm Differential Revision: https://reviews.llvm.org/D67261 llvm-svn: 371332
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