[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, 10 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTWriterStmt.cpp b/clang/lib/Serialization/ASTWriterStmt.cpp
index bd715461cb9..20a6b7d74ce 100644
--- a/clang/lib/Serialization/ASTWriterStmt.cpp
+++ b/clang/lib/Serialization/ASTWriterStmt.cpp
@@ -432,6 +432,16 @@ void ASTStmtWriter::VisitExpr(Expr *E) {
 
 void ASTStmtWriter::VisitConstantExpr(ConstantExpr *E) {
   VisitExpr(E);
+  Record.push_back(static_cast<uint64_t>(E->ConstantExprBits.ResultKind));
+  switch (E->ConstantExprBits.ResultKind) {
+  case ConstantExpr::RSK_Int64:
+    Record.push_back(E->Int64Result());
+    Record.push_back(E->ConstantExprBits.IsUnsigned |
+                     E->ConstantExprBits.BitWidth << 1);
+    break;
+  case ConstantExpr::RSK_APValue:
+    Record.AddAPValue(E->APValueResult());
+  }
   Record.AddStmt(E->getSubExpr());
   Code = serialization::EXPR_CONSTANT;
 }