[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, 3 insertions, 2 deletions

diff --git a/clang/lib/AST/APValue.cpp b/clang/lib/AST/APValue.cpp
index 5d5e67a8902..1993bba9bd1 100644
--- a/clang/lib/AST/APValue.cpp
+++ b/clang/lib/AST/APValue.cpp
@@ -456,7 +456,8 @@ void APValue::dump(raw_ostream &OS) const {
   llvm_unreachable("Unknown APValue kind!");
 }
 
-void APValue::printPretty(raw_ostream &Out, ASTContext &Ctx, QualType Ty) const{
+void APValue::printPretty(raw_ostream &Out, const ASTContext &Ctx,
+                          QualType Ty) const {
   switch (getKind()) {
   case APValue::None:
     Out << "<out of lifetime>";
@@ -675,7 +676,7 @@ void APValue::printPretty(raw_ostream &Out, ASTContext &Ctx, QualType Ty) const{
   llvm_unreachable("Unknown APValue kind!");
 }
 
-std::string APValue::getAsString(ASTContext &Ctx, QualType Ty) const {
+std::string APValue::getAsString(const ASTContext &Ctx, QualType Ty) const {
   std::string Result;
   llvm::raw_string_ostream Out(Result);
   printPretty(Out, Ctx, Ty);