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

[Eli Friedman via Phabricator via cfe-commits]

efriedma added inline comments.



Comment at: clang/lib/CodeGen/CGExprConstant.cpp:1128
+case CK_NoOp:
+case CK_NonAtomicToAtomic:
   return Visit(subExpr, destType);

I think I'd prefer to continue treating an undecayed function as an "lvalue", 
to keep things straightforward.  To that end, I'd prefer a separate 
"ConstLValueExprEmitter", or something like that, so ConstExprEmitter only 
visits rvalues.

The new emitter should reuse code from ConstLValueExprEmitter where possible.



Comment at: clang/lib/CodeGen/CGExprConstant.cpp:1247
+if (isa(VD))
+  return CGM.getModule().getNamedValue(VD->getName());
+return nullptr;

You 100% can't use `VD->getName()` like this; I'm shocked this isn't causing 
any test failures.  GetAddrOfFunction() resolves names correctly.


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

[Shafik Yaghmour via Phabricator via cfe-commits]

shafik added a comment.

Makes sense but I want @efriedma to look at as well.


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

[Nick Desaulniers via Phabricator via cfe-commits]

nickdesaulniers updated this revision to Diff 544909.
nickdesaulniers added a comment.

- update


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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 +1241,13 @@
 return llvm::ConstantInt::get(CGM.getLLVMContext(), I->getValue());
   }
 
+  llvm::Constant *VisitDeclRefExpr(DeclRefExpr *D, QualType T) {
+ValueDecl *VD = D->getDecl();
+if (isa(VD))
+  return CGM.getModule().getNamedValue(VD->getName());
+return nullptr;
+  }
+
   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");


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 +1241,13 @@
 return llvm::ConstantInt::get(CGM.getLLVMContext(), I->getValue());
   }
 
+  llvm::Constant *VisitDeclRefExpr(DeclRefExpr *D, QualType T) {
+ValueDecl *VD = D->getDecl();
+if (isa(VD))
+  return CGM.getModule().getNamedValue(VD->getName());
+return nullptr;
+  }
+
   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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[PATCH] D156482: [clang][CGExprConstant] handle FunctionToPointerDecay

[Nick Desaulniers via Phabricator via cfe-commits]

nickdesaulniers created this revision.
Herald added a project: All.
nickdesaulniers requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

Consider the following code:

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

And the corresponding AST:

  |-FunctionDecl 0x561e9cf12728  col:6 used foo 'void (void)'
  | `-CompoundStmt 0x561e9cf12818 
  `-VarDecl 0x561e9cf12958  col:8 bar 'void (*)(void)' cinit
`-ImplicitCastExpr 0x561e9cf129e0  'void (*)(void)' 

  `-DeclRefExpr 0x561e9cf129c0  '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(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(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(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");


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(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(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(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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