[clang] 333771f - [Sema] Avoid isNullPointerConstant invocation

[Nick Desaulniers via cfe-commits]

Author: Justin Stitt
Date: 2022-08-14T13:39:57-07:00
New Revision: 333771f3558c81390a0e5d715ad8d1e419050b66

URL: https://github.com/llvm/llvm-project/commit/333771f3558c81390a0e5d715ad8d1e419050b66
DIFF: https://github.com/llvm/llvm-project/commit/333771f3558c81390a0e5d715ad8d1e419050b66.diff

LOG: [Sema] Avoid isNullPointerConstant invocation

DiagnoseNullConversion is needlessly calling isNullPointerConstant which
is an expensive routine due to its calls to a constant evaluator --
which we don't need.

Building the Linux Kernel (x86_64) with this fix has improved build
times by ~2.1%. This is mainly due to the following methods no longer
needing to be called anywhere near as often:
1) ExprConstant::CheckICE (reduced CPU cycles by ~90%)
2) IntExprEvaluator::VisitBinaryOperator (reduced CPU cycles by ~50%)

Reviewed By: rtrieu, nickdesaulniers

Differential Revision: https://reviews.llvm.org/D131532

Added: 
    

Modified: 
    clang/lib/Sema/SemaChecking.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index a0ea35e1234f6..bb4ca8c1e4209 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -13355,9 +13355,10 @@ static void DiagnoseNullConversion(Sema &S, Expr *E, QualType T,
     return;
 
   // Check for NULL (GNUNull) or nullptr (CXX11_nullptr).
-  const Expr::NullPointerConstantKind NullKind =
-      E->isNullPointerConstant(S.Context, Expr::NPC_ValueDependentIsNotNull);
-  if (NullKind != Expr::NPCK_GNUNull && NullKind != Expr::NPCK_CXX11_nullptr)
+  const Expr *NewE = E->IgnoreParenImpCasts();
+  bool IsGNUNullExpr = isa<GNUNullExpr>(NewE);
+  bool HasNullPtrType = NewE->getType()->isNullPtrType();
+  if (!IsGNUNullExpr && !HasNullPtrType)
     return;
 
   // Return if target type is a safe conversion.
@@ -13374,7 +13375,7 @@ static void DiagnoseNullConversion(Sema &S, Expr *E, QualType T,
   CC = S.SourceMgr.getTopMacroCallerLoc(CC);
 
   // __null is usually wrapped in a macro.  Go up a macro if that is the case.
-  if (NullKind == Expr::NPCK_GNUNull && Loc.isMacroID()) {
+  if (IsGNUNullExpr && Loc.isMacroID()) {
     StringRef MacroName = Lexer::getImmediateMacroNameForDiagnostics(
         Loc, S.SourceMgr, S.getLangOpts());
     if (MacroName == "NULL")
@@ -13386,7 +13387,7 @@ static void DiagnoseNullConversion(Sema &S, Expr *E, QualType T,
     return;
 
   S.Diag(Loc, diag::warn_impcast_null_pointer_to_integer)
-      << (NullKind == Expr::NPCK_CXX11_nullptr) << T << SourceRange(CC)
+      << HasNullPtrType << T << SourceRange(CC)
       << FixItHint::CreateReplacement(Loc,
                                       S.getFixItZeroLiteralForType(T, Loc));
 }