forked from OSchip/llvm-project
715a5efaad
Summary: A DBG_VALUE that is referring to a physical register is valid up until the next def of the register, or the end of the basic block that it belongs to. LiveDebugVariables is computing live intervals (slot index ranges) for DBG_VALUE instructions, before regalloc, in order to be able to re-insert DBG_VALUE instructions again after regalloc. When the DBG_VALUE is mapping a variable to a physical register we do not need to compute the range. We should simply re-insert the DBG_VALUE at the start position. The problem that was found, resulting in this patch, was a situation when the DBG_VALUE was the last real use of the physical register. The computeIntervals/extendDef methods extended the range to cover the whole basic block, even though the physical register very well could be allocated to some virtual register inside the basic block. So the extended range could not be trusted. This patch is a preparation for https://reviews.llvm.org/D38229, where the goal is to insert DBG_VALUE after each new definition of a variable, even if the virtual registers that the variable was connected to has been coalesced into using the same physical register (e.g. due to two address instructions). For more info see https://bugs.llvm.org/show_bug.cgi?id=34545 Reviewers: aprantl, rnk, echristo Reviewed By: aprantl Subscribers: Ka-Ka, llvm-commits Differential Revision: https://reviews.llvm.org/D38140 llvm-svn: 314414 |
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