[Driver] Simplify -g level computation and its interaction with -gsplit-dwarf
Summary: When -gsplit-dwarf is used together with other -g options, in most cases the computed debug info level is decided by the last -g option, with one special case (see below). This patch drops that special case and thus makes it easy to reason about: // If a lower debug level -g comes after -gsplit-dwarf, in some cases // -gsplit-dwarf is cancelled. -gsplit-dwarf -g0 => 0 -gsplit-dwarf -gline-directives-only => DebugDirectivesOnly -gsplit-dwarf -gmlt -fsplit-dwarf-inlining => 1 -gsplit-dwarf -gmlt -fno-split-dwarf-inlining => 1 + split // If -gsplit-dwarf comes after -g options, with this patch, the net // effect is 2 + split for all combinations -g0 -gsplit-dwarf => 2 + split -gline-directives-only -gsplit-dwarf => 2 + split -gmlt -gsplit-dwarf -fsplit-dwarf-inlining => 2 + split -gmlt -gsplit-dwarf -fno-split-dwarf-inlining => 1 + split (before) 2 + split (after) The last case has been changed. In general, if the user intends to lower debug info level, place that -g option after -gsplit-dwarf. Some context: In gcc, the last of -gsplit-dwarf -g0 -g1 -g2 -g3 -ggdb[0-3] -gdwarf-* ... decides the debug info level (-gsplit-dwarf -gdwarf-* have level 2). It is a bit unfortunate that -gsplit-dwarf -gdwarf-* ... participate in the level computation but that is the status quo. Reviewers: dblaikie, echristo, probinson Reviewed By: dblaikie, probinson Subscribers: probinson, aprantl, jdoerfert, cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D59923 llvm-svn: 358544
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