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[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
This commit is contained in:
Justin Stitt 2022-08-14 13:28:49 -07:00 committed by Nick Desaulniers
parent 0299ebc1bd
commit 333771f355
1 changed files with 6 additions and 5 deletions
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11
clang/lib/Sema/SemaChecking.cpp
View File

@ -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));
}