[llvm] [SelectionDAG] Add an ISD::CLEAR_CACHE node to lower llvm.clear_cache (PR #93795)

[Matt Arsenault via llvm-commits]

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@@ -7516,11 +7516,18 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
   case Intrinsic::invariant_end:
     // Discard region information.
     return;
-  case Intrinsic::clear_cache:
-    /// FunctionName may be null.
-    if (const char *FunctionName = TLI.getClearCacheBuiltinName())
-      lowerCallToExternalSymbol(I, FunctionName);
+  case Intrinsic::clear_cache: {
+    SDValue InputChain = DAG.getRoot();
+    Value *Start = I.getArgOperand(0);
+    SDValue StartVal = getValue(Start);
+    Value *End = I.getArgOperand(1);
+    SDValue EndVal = getValue(End);
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arsenm wrote:

Avoid the temporary Value variable? StartVal = getValue(getArgOperand()) 

https://github.com/llvm/llvm-project/pull/93795