[clang] 11e52ec - [clang] Short-circuit trivial constructors when evaluating arrays
Timm Bäder via cfe-commits
cfe-commits at lists.llvm.org
Wed Aug 3 01:41:18 PDT 2022
Author: Timm Bäder
Date: 2022-08-03T10:38:15+02:00
New Revision: 11e52ecf74e942b738fa8496960bbb2f0a7373de
URL: https://github.com/llvm/llvm-project/commit/11e52ecf74e942b738fa8496960bbb2f0a7373de
DIFF: https://github.com/llvm/llvm-project/commit/11e52ecf74e942b738fa8496960bbb2f0a7373de.diff
LOG: [clang] Short-circuit trivial constructors when evaluating arrays
VisitCXXConstructExpr() will later do something similar, but for large
arrays, we should try to do it once an not for every element.
Fixes #56774
Differential Revision: https://reviews.llvm.org/D130791
Added:
Modified:
clang/docs/ReleaseNotes.rst
clang/lib/AST/ExprConstant.cpp
Removed:
################################################################################
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 9dc08639dafb4..2c439a01d7216 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -54,6 +54,9 @@ Bug Fixes
`Issue 56800 <https://github.com/llvm/llvm-project/issues/56800>`_.
- Fix `#56772 <https://github.com/llvm/llvm-project/issues/56772>`_ - invalid
destructor names were incorrectly accepted on template classes.
+- Improve compile-times with large dynamic array allocations with trivial
+ constructors. This fixes
+ `Issue 56774<https://github.com/llvm/llvm-project/issues/56774>`_.
Improvements to Clang's diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 32a04ca9e3de3..efaccf52132b3 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -10833,6 +10833,9 @@ bool ArrayExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E,
if (FinalSize == 0)
return true;
+ bool HasTrivialConstructor = CheckTrivialDefaultConstructor(
+ Info, E->getExprLoc(), E->getConstructor(),
+ E->requiresZeroInitialization());
LValue ArrayElt = Subobject;
ArrayElt.addArray(Info, E, CAT);
// We do the whole initialization in two passes, first for just one element,
@@ -10856,19 +10859,26 @@ bool ArrayExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E,
for (unsigned I = OldElts; I < N; ++I)
Value->getArrayInitializedElt(I) = Filler;
- // Initialize the elements.
- for (unsigned I = OldElts; I < N; ++I) {
- if (!VisitCXXConstructExpr(E, ArrayElt,
- &Value->getArrayInitializedElt(I),
- CAT->getElementType()) ||
- !HandleLValueArrayAdjustment(Info, E, ArrayElt,
- CAT->getElementType(), 1))
- return false;
- // When checking for const initilization any diagnostic is considered
- // an error.
- if (Info.EvalStatus.Diag && !Info.EvalStatus.Diag->empty() &&
- !Info.keepEvaluatingAfterFailure())
- return false;
+ if (HasTrivialConstructor && N == FinalSize) {
+ // If we have a trivial constructor, only evaluate it once and copy
+ // the result into all the array elements.
+ APValue &FirstResult = Value->getArrayInitializedElt(0);
+ for (unsigned I = OldElts; I < FinalSize; ++I)
+ Value->getArrayInitializedElt(I) = FirstResult;
+ } else {
+ for (unsigned I = OldElts; I < N; ++I) {
+ if (!VisitCXXConstructExpr(E, ArrayElt,
+ &Value->getArrayInitializedElt(I),
+ CAT->getElementType()) ||
+ !HandleLValueArrayAdjustment(Info, E, ArrayElt,
+ CAT->getElementType(), 1))
+ return false;
+ // When checking for const initilization any diagnostic is considered
+ // an error.
+ if (Info.EvalStatus.Diag && !Info.EvalStatus.Diag->empty() &&
+ !Info.keepEvaluatingAfterFailure())
+ return false;
+ }
}
}
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