6bbe1bc940
The information that's used to generate DWARF location lists is very ssa.Value centric; it uses Values as start and end coordinates to define ranges. That mostly works fine, but control flow instructions don't come from Values, so the ranges couldn't cover them. Control flow instructions are generated when the SSA representation is converted to assembly, so that's the best place to extend the ranges to cover them. (Before that, there's nothing to refer to, and afterward the boundaries between blocks have been lost.) That requires block information in the debugInfo type, which then flows down to make everything else awkward. On the plus side, there's a little less copying slices around than there used to be, so it should be a little faster. Previously, the ranges for empty blocks were not very meaningful. That was fine, because they had no Values to cover, so no debug information was generated for them. But they do have control flow instructions (that's why they exist) and so now it's important that the information be correct. Introduce two sentinel values, BlockStart and BlockEnd, that denote the boundary of a block, even if the block is empty. BlockEnd replaces the previous SurvivedBlock flag. There's one more problem: the last instruction in the function will be a control flow instruction, so any live ranges need to be extended past it. But there's no instruction after it to use as the end of the range. Instead, leave the EndProg field of those ranges as nil and fix it up to point to past the end of the assembled text at the very last moment. Change-Id: I81f884020ff36fd6fe8d7888fc57c99412c4245b Reviewed-on: https://go-review.googlesource.com/63010 Reviewed-by: Alessandro Arzilli <alessandro.arzilli@gmail.com> Reviewed-by: David Chase <drchase@google.com> Run-TryBot: Heschi Kreinick <heschi@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> |
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The Go Programming Language
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