[PATCH] D92338: [FastISel] NFC: Clean up unnecessary bookkeeping

[Paul Robinson via Phabricator via llvm-commits]

probinson created this revision.
probinson added a reviewer: rnk.
Herald added subscribers: jfb, hiraditya.
Herald added a project: LLVM.
probinson requested review of this revision.

Now that we flush the local value map for every instruction, we don't
need any extra flushes for specific cases.  Also, LastFlushPoint is
not used for anything.  Follow-ups to #dc35368 (D91734 <https://reviews.llvm.org/D91734>).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D92338

Files:
  llvm/include/llvm/CodeGen/FastISel.h
  llvm/lib/CodeGen/SelectionDAG/FastISel.cpp


Index: llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -215,7 +215,6 @@
   LastLocalValue = EmitStartPt;
   recomputeInsertPt();
   SavedInsertPt = FuncInfo.InsertPt;
-  LastFlushPoint = FuncInfo.InsertPt;
 }
 
 bool FastISel::hasTrivialKill(const Value *V) {
@@ -437,8 +436,6 @@
   assert(I.isValid() && E.isValid() && std::distance(I, E) > 0 &&
          "Invalid iterator!");
   while (I != E) {
-    if (LastFlushPoint == I)
-      LastFlushPoint = E;
     if (SavedInsertPt == I)
       SavedInsertPt = E;
     if (EmitStartPt == I)
@@ -1189,11 +1186,6 @@
 
   // Handle simple inline asms.
   if (const InlineAsm *IA = dyn_cast<InlineAsm>(Call->getCalledOperand())) {
-    // If the inline asm has side effects, then make sure that no local value
-    // lives across by flushing the local value map.
-    if (IA->hasSideEffects())
-      flushLocalValueMap();
-
     // Don't attempt to handle constraints.
     if (!IA->getConstraintString().empty())
       return false;
@@ -1223,15 +1215,6 @@
   if (const auto *II = dyn_cast<IntrinsicInst>(Call))
     return selectIntrinsicCall(II);
 
-  // Usually, it does not make sense to initialize a value,
-  // make an unrelated function call and use the value, because
-  // it tends to be spilled on the stack. So, we move the pointer
-  // to the last local value to the beginning of the block, so that
-  // all the values which have already been materialized,
-  // appear after the call. It also makes sense to skip intrinsics
-  // since they tend to be inlined.
-  flushLocalValueMap();
-
   return lowerCall(Call);
 }
 
@@ -1388,20 +1371,6 @@
     return selectXRayCustomEvent(II);
   case Intrinsic::xray_typedevent:
     return selectXRayTypedEvent(II);
-
-  case Intrinsic::memcpy:
-  case Intrinsic::memcpy_element_unordered_atomic:
-  case Intrinsic::memcpy_inline:
-  case Intrinsic::memmove:
-  case Intrinsic::memmove_element_unordered_atomic:
-  case Intrinsic::memset:
-  case Intrinsic::memset_element_unordered_atomic:
-    // Flush the local value map just like we do for regular calls,
-    // to avoid excessive spills and reloads.
-    // These intrinsics mostly turn into library calls at O0; and
-    // even memcpy_inline should be treated like one for this purpose.
-    flushLocalValueMap();
-    break;
   }
 
   return fastLowerIntrinsicCall(II);
Index: llvm/include/llvm/CodeGen/FastISel.h
===================================================================
--- llvm/include/llvm/CodeGen/FastISel.h
+++ llvm/include/llvm/CodeGen/FastISel.h
@@ -224,10 +224,6 @@
   /// makes sense (for example, on function calls)
   MachineInstr *EmitStartPt;
 
-  /// Last local value flush point. On a subsequent flush, no local value will
-  /// sink past this point.
-  MachineBasicBlock::iterator LastFlushPoint;
-
 public:
   virtual ~FastISel();
 


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