[llvm] Add a pass to collect dropped var statistics for MIR (PR #126686)

[Shubham Sandeep Rastogi via llvm-commits]

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@@ -91,7 +96,15 @@ bool MachineFunctionPass::runOnFunction(Function &F) {
 
   MFProps.reset(ClearedProperties);
 
-  bool RV = runOnMachineFunction(MF);
+  bool RV;
+  if (DroppedVarStatsMIR) {
+    auto PassName = getPassName();
+    DroppedVarStatsMF.runBeforePass(PassName, &MF);
+    RV = runOnMachineFunction(MF);
+    DroppedVarStatsMF.runAfterPass(PassName, &MF);
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rastogishubham wrote:

https://llvm-compile-time-tracker.com/compare.php?from=5e59fa57d29e159f41957958ba541049f85652d6&to=94f4cf922deb8997ff10525b58432cf2eab8bee2&stat=instructions:u 

It is down to 0.04%

https://github.com/llvm/llvm-project/pull/126686