[clang] Add storage for APValue in ConstantExpr

Summary:
When using ConstantExpr we often need the result of the expression to be kept in the AST. Currently this is done on a by the node that needs the result and has been done multiple times for enumerator, for constexpr variables... . This patch adds to ConstantExpr the ability to store the result of evaluating the expression. no functional changes expected.

Changes:
 - Add trailling object to ConstantExpr that can hold an APValue or an uint64_t. the uint64_t is here because most ConstantExpr yield integral values so there is an optimized layout for integral values.
 - Add basic* serialization support for the trailing result.
 - Move conversion functions from an enum to a fltSemantics from clang::FloatingLiteral to llvm::APFloatBase. this change is to make it usable for serializing APValues.
 - Add basic* Import support for the trailing result.
 - ConstantExpr created in CheckConvertedConstantExpression now stores the result in the ConstantExpr Node.
 - Adapt AST dump to print the result when present.

basic* : None, Indeterminate, Int, Float, FixedPoint, ComplexInt, ComplexFloat,
the result is not yet used anywhere but for -ast-dump.

Reviewers: rsmith, martong, shafik

Reviewed By: rsmith

Subscribers: rnkovacs, hiraditya, dexonsmith, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D62399

llvm-svn: 363493

1 files changed, 7 insertions, 0 deletions

diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index b43491d061a..d3c79eac903 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -6376,6 +6376,13 @@ ExpectedStmt ASTNodeImporter::VisitConstantExpr(ConstantExpr *E) {
   Expr *ToSubExpr;
   std::tie(ToSubExpr) = *Imp;
 
+  // TODO : Handle APValue::ValueKind that require importing.
+  APValue::ValueKind Kind = E->getResultAPValueKind();
+  if (Kind == APValue::Int || Kind == APValue::Float ||
+      Kind == APValue::FixedPoint || Kind == APValue::ComplexFloat ||
+      Kind == APValue::ComplexInt)
+    return ConstantExpr::Create(Importer.getToContext(), ToSubExpr,
+                                E->getAPValueResult());
   return ConstantExpr::Create(Importer.getToContext(), ToSubExpr);
 }