[PATCH] D138115: [clang] Short-circuit evaluation in ::EvaluateAsConstantExpr

[Timm Bäder via Phabricator via cfe-commits]

tbaeder created this revision.
tbaeder added reviewers: aaron.ballman, erichkeane.
Herald added a project: All.
tbaeder requested review of this revision.
Herald added a project: clang.
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This adds another case to `FastEvaluateAsRValue()` for boolean expressions as well as calls `FastEvaluateAsRValue()` in `Expr::EvaluateAsConstantExpr()` as well.

This way we can short-circuit evaluating simple integer and boolean literals here.

I don't have before/after numbers for compilation times, since my local builds have asan enabled (so valgrind doesn't work) and I lost access to the my asan-less build. But it shouldn't be worse than before... right?

Sorry, can't find better reviewers to add.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D138115

Files:
  clang/lib/AST/ExprConstant.cpp


Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -15056,6 +15056,12 @@
     return true;
   }
 
+  if (const auto *L = dyn_cast<CXXBoolLiteralExpr>(Exp)) {
+    Result.Val = APValue(APSInt(APInt(1, L->getValue())));
+    IsConst = true;
+    return true;
+  }
+
   // This case should be rare, but we need to check it before we check on
   // the type below.
   if (Exp->getType().isNull()) {
@@ -15240,6 +15246,9 @@
                                   ConstantExprKind Kind) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
+  bool IsConst;
+  if (FastEvaluateAsRValue(this, Result, Ctx, IsConst))
+    return true;
 
   ExprTimeTraceScope TimeScope(this, Ctx, "EvaluateAsConstantExpr");
   EvalInfo::EvaluationMode EM = EvalInfo::EM_ConstantExpression;


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