[llvm] [KeyInstr][DwarfDebug] Add is_stmt emission support (PR #133495)

[Orlando Cazalet-Hyams via llvm-commits]

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@@ -2333,6 +2352,170 @@ DwarfDebug::emitInitialLocDirective(const MachineFunction &MF, unsigned CUID) {
   return PrologEndLoc;
 }
 
+void DwarfDebug::findKeyInstructions(const MachineFunction *MF) {
+  // New function - reset KeyInstructions.
+  KeyInstructions.clear();
+
+  // The current candidate is_stmt instructions for each source atom.
+  // Map {(InlinedAt, Group): (Rank, Instructions)}.
+  DenseMap<std::pair<DILocation *, uint32_t>,
+           std::pair<uint16_t, SmallVector<const MachineInstr *>>>
+      GroupCandidates;
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OCHyams wrote:

Seems much of a muchness. http://llvm-compile-time-tracker.com/compare.php?from=864910b2187803587013f0c6a8ed57361670dc08&to=4ca6a9fa05d51d62b27a48125f97d92812f0972d&stat=instructions%3Au#. The clang build indicates a preference for small-size of 2 rather than 1 when looking at max rss, but I'm not sure I trust that number as I'm pretty sure the clang self host build is release + thinLTO (no -g).

https://github.com/llvm/llvm-project/pull/133495