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[DebugInfo] Discard invalid DBG_VALUE instructions in LiveDebugVariables #77
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Summary: This is a workaround for pr36417 https://bugs.llvm.org/show_bug.cgi?id=36417 LiveDebugVariables will now verify that the DBG_VALUE instructions are sane (prior to register allocation) by asking LIS if a virtual register used in the DBG_VALUE is live (or dead def) in the slot index before the DBG_VALUE. If it isn't sane the DBG_VALUE is discarded. One pass that was identified as introducing non-sane DBG_VALUE instructtons, when analysing pr36417, was the DAG->DAG Instruction Selection. It sometimes inserts DBG_VALUE instructions referring to a virtual register that is defined later in the same basic block. So it is a use before def kind of problem. The DBG_VALUE is typically inserted in the beginning of a basic block when this happens. The problem can be seen in the test case test/DebugInfo/X86/dbg-value-inlined-parameter.ll Reviewers: aprantl, rnk, probinson Reviewed By: aprantl Subscribers: vsk, davide, alexcrichton, Ka-Ka, eraman, llvm-commits, JDevlieghere Differential Revision: https://reviews.llvm.org/D43956 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@326769 91177308-0d34-0410-b5e6-96231b3b80d8
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Summary:
This is a workaround for pr36417
https://bugs.llvm.org/show_bug.cgi?id=36417
LiveDebugVariables will now verify that the DBG_VALUE instructions
are sane (prior to register allocation) by asking LIS if a virtual
register used in the DBG_VALUE is live (or dead def) in the slot
index before the DBG_VALUE. If it isn't sane the DBG_VALUE is
discarded.
One pass that was identified as introducing non-sane DBG_VALUE
instructtons, when analysing pr36417, was the DAG->DAG Instruction
Selection. It sometimes inserts DBG_VALUE instructions referring to
a virtual register that is defined later in the same basic block.
So it is a use before def kind of problem. The DBG_VALUE is
typically inserted in the beginning of a basic block when this
happens. The problem can be seen in the test case
test/DebugInfo/X86/dbg-value-inlined-parameter.ll
Reviewers: aprantl, rnk, probinson
Reviewed By: aprantl
Subscribers: vsk, davide, alexcrichton, Ka-Ka, eraman, llvm-commits, JDevlieghere
Differential Revision: https://reviews.llvm.org/D43956
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@326769 91177308-0d34-0410-b5e6-96231b3b80d8