[clang][bytecode] Try to load primitive values directly (#151833)

Instead of doing a GetPtrLocal + Load or GetPtrGlobal + Load pair, try
to load the value directly.

1 files changed, 23 insertions, 4 deletions

diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index 6e451ac..7a5bd4d 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -201,6 +201,28 @@ bool Compiler<Emitter>::VisitCastExpr(const CastExpr *CE) {
       return this->emitInvalidCast(CastKind::Volatile, /*Fatal=*/true, CE);
 
     OptPrimType SubExprT = classify(SubExpr->getType());
+    // Try to load the value directly. This is purely a performance
+    // optimization.
+    if (SubExprT) {
+      if (const auto *DRE = dyn_cast<DeclRefExpr>(SubExpr)) {
+        const ValueDecl *D = DRE->getDecl();
+        bool IsReference = D->getType()->isReferenceType();
+
+        if (!IsReference) {
+          if (Context::shouldBeGloballyIndexed(D)) {
+            if (auto GlobalIndex = P.getGlobal(D))
+              return this->emitGetGlobal(*SubExprT, *GlobalIndex, CE);
+          } else if (auto It = Locals.find(D); It != Locals.end()) {
+            return this->emitGetLocal(*SubExprT, It->second.Offset, CE);
+          } else if (const auto *PVD = dyn_cast<ParmVarDecl>(D)) {
+            if (auto It = this->Params.find(PVD); It != this->Params.end()) {
+              return this->emitGetParam(*SubExprT, It->second.Offset, CE);
+            }
+          }
+        }
+      }
+    }
+
     // Prepare storage for the result.
     if (!Initializing && !SubExprT) {
       std::optional<unsigned> LocalIndex = allocateLocal(SubExpr);
@@ -3857,10 +3879,7 @@ template <class Emitter>
 bool Compiler<Emitter>::VisitAddrLabelExpr(const AddrLabelExpr *E) {
   assert(E->getType()->isVoidPointerType());
 
-  unsigned Offset =
-      allocateLocalPrimitive(E->getLabel(), PT_Ptr, /*IsConst=*/true);
-
-  return this->emitGetLocal(PT_Ptr, Offset, E);
+  return this->emitDummyPtr(E, E);
 }
 
 template <class Emitter>