[PATCH] D76169: [WIP][AST] Allow ExprConstant to evaluate structs in C.

[Eli Friedman via Phabricator via cfe-commits]

efriedma created this revision.
efriedma added a reviewer: nickdesaulniers.
Herald added a project: clang.

Just a proof of concept to show this works.  Handles all the examples from D76096 <https://reviews.llvm.org/D76096>, as far as I can tell.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D76169

Files:
  clang/lib/AST/ExprConstant.cpp
  clang/lib/CodeGen/CGExprConstant.cpp


Index: clang/lib/CodeGen/CGExprConstant.cpp
===================================================================
--- clang/lib/CodeGen/CGExprConstant.cpp
+++ clang/lib/CodeGen/CGExprConstant.cpp
@@ -2084,8 +2084,7 @@
   case APValue::Union:
     return ConstStructBuilder::BuildStruct(*this, Value, DestType);
   case APValue::Array: {
-    const ConstantArrayType *CAT =
-        CGM.getContext().getAsConstantArrayType(DestType);
+    const ArrayType *AT = CGM.getContext().getAsArrayType(DestType);
     unsigned NumElements = Value.getArraySize();
     unsigned NumInitElts = Value.getArrayInitializedElts();
 
@@ -2093,7 +2092,7 @@
     llvm::Constant *Filler = nullptr;
     if (Value.hasArrayFiller()) {
       Filler = tryEmitAbstractForMemory(Value.getArrayFiller(),
-                                        CAT->getElementType());
+                                        AT->getElementType());
       if (!Filler)
         return nullptr;
     }
@@ -2108,7 +2107,7 @@
     llvm::Type *CommonElementType = nullptr;
     for (unsigned I = 0; I < NumInitElts; ++I) {
       llvm::Constant *C = tryEmitPrivateForMemory(
-          Value.getArrayInitializedElt(I), CAT->getElementType());
+          Value.getArrayInitializedElt(I), AT->getElementType());
       if (!C) return nullptr;
 
       if (I == 0)
@@ -2120,6 +2119,8 @@
 
     // This means that the array type is probably "IncompleteType" or some
     // type that is not ConstantArray.
+    const ConstantArrayType *CAT =
+        CGM.getContext().getAsConstantArrayType(DestType);
     if (CAT == nullptr && CommonElementType == nullptr && !NumInitElts) {
       const ArrayType *AT = CGM.getContext().getAsArrayType(DestType);
       CommonElementType = CGM.getTypes().ConvertType(AT->getElementType());
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -13740,14 +13740,6 @@
     return true;
   }
 
-  // FIXME: Evaluating values of large array and record types can cause
-  // performance problems. Only do so in C++11 for now.
-  if (Exp->isRValue() && (Exp->getType()->isArrayType() ||
-                          Exp->getType()->isRecordType()) &&
-      !Ctx.getLangOpts().CPlusPlus11) {
-    IsConst = false;
-    return true;
-  }
   return false;
 }
 
@@ -13913,12 +13905,6 @@
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
-  // FIXME: Evaluating initializers for large array and record types can cause
-  // performance problems. Only do so in C++11 for now.
-  if (isRValue() && (getType()->isArrayType() || getType()->isRecordType()) &&
-      !Ctx.getLangOpts().CPlusPlus11)
-    return false;
-
   Expr::EvalStatus EStatus;
   EStatus.Diag = &Notes;
 


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