[PATCH] D156482: [clang][CGExprConstant] handle FunctionToPointerDecay

[Nick Desaulniers via Phabricator via cfe-commits]

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Consider the following code:

  void foo (void) {}
  void (*bar)(void) = foo;

And the corresponding AST:

  |-FunctionDecl 0x561e9cf12728 <x.c:14:1, col:18> col:6 used foo 'void (void)'
  | `-CompoundStmt 0x561e9cf12818 <col:17, col:18>
  `-VarDecl 0x561e9cf12958 <line:15:1, col:21> col:8 bar 'void (*)(void)' cinit
    `-ImplicitCastExpr 0x561e9cf129e0 <col:21> 'void (*)(void)' <FunctionToPointerDecay>
      `-DeclRefExpr 0x561e9cf129c0 <col:21> 'void (void)' Function 0x561e9cf12728 'foo' 'void (void)'

The ImplicitCastExpr of FunctionToPointerDecay is obviously const.
Lookup the corresponding llvm::Function in the Module by name.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D156482

Files:
  clang/lib/CodeGen/CGExprConstant.cpp


Index: clang/lib/CodeGen/CGExprConstant.cpp
===================================================================
--- clang/lib/CodeGen/CGExprConstant.cpp
+++ clang/lib/CodeGen/CGExprConstant.cpp
@@ -1122,9 +1122,10 @@
     }
 
     case CK_AtomicToNonAtomic:
-    case CK_NonAtomicToAtomic:
-    case CK_NoOp:
     case CK_ConstructorConversion:
+    case CK_FunctionToPointerDecay:
+    case CK_NoOp:
+    case CK_NonAtomicToAtomic:
       return Visit(subExpr, destType);
 
     case CK_ArrayToPointerDecay:
@@ -1189,7 +1190,6 @@
     case CK_CPointerToObjCPointerCast:
     case CK_BlockPointerToObjCPointerCast:
     case CK_AnyPointerToBlockPointerCast:
-    case CK_FunctionToPointerDecay:
     case CK_BaseToDerived:
     case CK_DerivedToBase:
     case CK_UncheckedDerivedToBase:
@@ -1241,6 +1241,26 @@
     return llvm::ConstantInt::get(CGM.getLLVMContext(), I->getValue());
   }
 
+  llvm::Constant *VisitDeclRefExpr(DeclRefExpr *D, QualType T) {
+    //llvm::dbgs() << __func__ << "\n";
+    //D->dump();
+    //VD->dump();
+    ValueDecl *VD = D->getDecl();
+    if (isa<FunctionDecl>(VD)) {
+      return CGM.getModule().getNamedValue(VD->getName());
+      //llvm::Module &M = CGM.getModule();
+      //llvm::GlobalValue *GV = M.getNamedValue(VD->getName());
+      //return GV;
+    }
+    //D->getSubExpr()->dump();
+    //llvm::dbgs() << isa<llvm::Function>(D) << "\n";
+    //llvm::GlobalValue *GV = CGM.getModule().getNamedValue(D->getName());
+    return nullptr;
+    //return nullptr;
+    //llvm::Value *V = Emitter.CGF->EmitDeclRefLValue(D).getPointer(*Emitter.CGF);
+    //return dyn_cast_or_null<llvm::Constant>(V);
+  }
+
   llvm::Constant *EmitArrayInitialization(InitListExpr *ILE, QualType T) {
     auto *CAT = CGM.getContext().getAsConstantArrayType(ILE->getType());
     assert(CAT && "can't emit array init for non-constant-bound array");


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