[llvm] [NFC][AlwaysInliner] Reduce AlwaysInliner memory consumption. (PR #96958)

[Daniil Fukalov via llvm-commits]

================
@@ -46,64 +47,73 @@ bool AlwaysInlineImpl(
     if (F.isPresplitCoroutine())
       continue;
 
-    if (!F.isDeclaration() && isInlineViable(F).isSuccess()) {
-      Calls.clear();
-
-      for (User *U : F.users())
-        if (auto *CB = dyn_cast<CallBase>(U))
-          if (CB->getCalledFunction() == &F &&
-                CB->hasFnAttr(Attribute::AlwaysInline) &&
-                !CB->getAttributes().hasFnAttr(Attribute::NoInline))
-              Calls.insert(CB);
-
-      for (CallBase *CB : Calls) {
-        Function *Caller = CB->getCaller();
-        OptimizationRemarkEmitter ORE(Caller);
-        DebugLoc DLoc = CB->getDebugLoc();
-        BasicBlock *Block = CB->getParent();
-
-        InlineFunctionInfo IFI(GetAssumptionCache, &PSI,
-                               GetBFI ? &GetBFI(*Caller) : nullptr,
-                               GetBFI ? &GetBFI(F) : nullptr);
-
-        InlineResult Res = InlineFunction(*CB, IFI, /*MergeAttributes=*/true,
-                                          &GetAAR(F), InsertLifetime);
-        if (!Res.isSuccess()) {
-          ORE.emit([&]() {
-            return OptimizationRemarkMissed(DEBUG_TYPE, "NotInlined", DLoc,
-                                            Block)
-                   << "'" << ore::NV("Callee", &F) << "' is not inlined into '"
-                   << ore::NV("Caller", Caller)
-                   << "': " << ore::NV("Reason", Res.getFailureReason());
-          });
-          continue;
-        }
-
-        emitInlinedIntoBasedOnCost(
-            ORE, DLoc, Block, F, *Caller,
-            InlineCost::getAlways("always inline attribute"),
-            /*ForProfileContext=*/false, DEBUG_TYPE);
+    if (!F.isDeclaration() && isInlineViable(F).isSuccess())
+      WorkList.push_back(&F);
+  }
 
-        Changed = true;
+  for (Function *F : WorkList) {
+    Calls.clear();
+
+    for (User *U : F->users())
+      if (auto *CB = dyn_cast<CallBase>(U))
+        if (CB->getCalledFunction() == F &&
+              CB->hasFnAttr(Attribute::AlwaysInline) &&
+              !CB->getAttributes().hasFnAttr(Attribute::NoInline))
+            Calls.insert(CB);
+
+    for (CallBase *CB : Calls) {
+      Function *Caller = CB->getCaller();
+      OptimizationRemarkEmitter ORE(Caller);
+      DebugLoc DLoc = CB->getDebugLoc();
+      BasicBlock *Block = CB->getParent();
+
+      InlineFunctionInfo IFI(GetAssumptionCache, &PSI,
+                              GetBFI ? &GetBFI(*Caller) : nullptr,
+                              GetBFI ? &GetBFI(*F) : nullptr);
+
+      InlineResult Res = InlineFunction(*CB, IFI, /*MergeAttributes=*/true,
+                                        &GetAAR(*F), InsertLifetime);
+      if (!Res.isSuccess()) {
+        ORE.emit([&]() {
+          return OptimizationRemarkMissed(DEBUG_TYPE, "NotInlined", DLoc,
+                                          Block)
+                  << "'" << ore::NV("Callee", F) << "' is not inlined into '"
+                  << ore::NV("Caller", Caller)
+                  << "': " << ore::NV("Reason", Res.getFailureReason());
+        });
+        continue;
       }
 
-      if (F.hasFnAttribute(Attribute::AlwaysInline)) {
-        // Remember to try and delete this function afterward. This both avoids
-        // re-walking the rest of the module and avoids dealing with any
-        // iterator invalidation issues while deleting functions.
-        InlinedFunctions.push_back(&F);
+      emitInlinedIntoBasedOnCost(
+          ORE, DLoc, Block, *F, *Caller,
+          InlineCost::getAlways("always inline attribute"),
+          /*ForProfileContext=*/false, DEBUG_TYPE);
+
+      Changed = true;
+    }
+
+    F->removeDeadConstantUsers();
+    if (F->hasFnAttribute(Attribute::AlwaysInline) && F->isDefTriviallyDead()) {
+      // Remember to try and delete this function afterward. This both avoids
+      // re-walking the rest of the module and avoids dealing with any
+      // iterator invalidation issues while deleting functions.
+      if (F->hasComdat()){
+        InlinedFunctions.push_back(F);
+      } else {
+        M.getFunctionList().erase(F);
+        Changed = true;
       }
     }
   }
 
-  // Remove any live functions.
+  // Final cleanup stage. Firstly, remove any live functions.
   erase_if(InlinedFunctions, [&](Function *F) {
     F->removeDeadConstantUsers();
----------------
dfukalov wrote:

Yes, you're right, thanks, removed this part.

https://github.com/llvm/llvm-project/pull/96958