[PATCH] D133321: [Assignment Tracking][24/*] Always RemoveRedundantDbgInstrs in instcombine in assignment tracking builds

[Orlando Cazalet-Hyams via Phabricator via llvm-commits]

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This reduces peak memory overhead by 15% when building CTMark's tramp3d-v4 with `-O2 -g` with assignment tracking enabled.

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When building CTMark's tramp3d-v4 (with -emit-llvm and RelWithDebInfo flags) with this patch stack the peak memory consumption increases by just under 1.5% when assignment tracking is enabled, and the run time difference (of the compiler) is negligible.


https://reviews.llvm.org/D133321

Files:
  llvm/lib/Transforms/InstCombine/InstructionCombining.cpp


Index: llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -4350,6 +4350,13 @@
   bool MadeIRChange = false;
   if (ShouldLowerDbgDeclare)
     MadeIRChange = LowerDbgDeclare(F);
+  // LowerDbgDeclare calls RemoveRedundantDbgInstrs, but LowerDbgDeclare will
+  // almost never return true when running an assignment tracking build. Take
+  // this opportunity to do some clean up for assignment tracking builds too.
+  if (!MadeIRChange && getEnableAssignmentTracking()) {
+    for (auto &BB : F)
+      RemoveRedundantDbgInstrs(&BB);
+  }
 
   // Iterate while there is work to do.
   unsigned Iteration = 0;


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