https://github.com/andykaylor created
https://github.com/llvm/llvm-project/pull/155668
This patch updates the loops in EmitCtorPrologue to use range-based for loops
rather than looping over a single iterator which was being shared between three
loops. Setting up three separate ranges adds a very small amount of overhead,
but it improves the readability and maintainability of the code.
>From 7a3f59c3f250f9730dc3479f2b5e1b28ec2f2354 Mon Sep 17 00:00:00 2001
From: Andy Kaylor <akay...@nvidia.com>
Date: Wed, 27 Aug 2025 10:28:55 -0700
Subject: [PATCH] [Clang][CodeGen]NFC] Modernize loops in EmitCtorPrologue
This patch updates the loops in EmitCtorPrologue to use range-based for
loops rather than looping over a single iterator which was being shared
between three loops. Setting up three separate ranges adds a very small
amount of overhead, but it improves the readability and maintainability
of the code.
---
clang/lib/CodeGen/CGClass.cpp | 43 ++++++++++++++++++++++++-----------
1 file changed, 30 insertions(+), 13 deletions(-)
diff --git a/clang/lib/CodeGen/CGClass.cpp b/clang/lib/CodeGen/CGClass.cpp
index bae55aa1e1928..b4a6acc0f2d5f 100644
--- a/clang/lib/CodeGen/CGClass.cpp
+++ b/clang/lib/CodeGen/CGClass.cpp
@@ -1271,10 +1271,7 @@ void CodeGenFunction::EmitCtorPrologue(const
CXXConstructorDecl *CD,
const CXXRecordDecl *ClassDecl = CD->getParent();
- CXXConstructorDecl::init_const_iterator B = CD->init_begin(),
- E = CD->init_end();
-
- // Virtual base initializers first, if any. They aren't needed if:
+ // Virtual base initializers aren't needed if:
// - This is a base ctor variant
// - There are no vbases
// - The class is abstract, so a complete object of it cannot be constructed
@@ -1296,15 +1293,36 @@ void CodeGenFunction::EmitCtorPrologue(const
CXXConstructorDecl *CD,
assert(BaseCtorContinueBB);
}
- for (; B != E && (*B)->isBaseInitializer() && (*B)->isBaseVirtual(); B++) {
+ // Create three separate ranges for the different types of initializers.
+ auto AllInits = CD->inits();
+
+ // Find the boundaries between the three groups.
+ auto VirtualBaseEnd = std::find_if(
+ AllInits.begin(), AllInits.end(), [](const CXXCtorInitializer *Init) {
+ return !(Init->isBaseInitializer() && Init->isBaseVirtual());
+ });
+
+ auto NonVirtualBaseEnd = std::find_if(VirtualBaseEnd, AllInits.end(),
+ [](const CXXCtorInitializer *Init) {
+ return !Init->isBaseInitializer();
+ });
+
+ // Create the three ranges.
+ auto VirtualBaseInits = llvm::make_range(AllInits.begin(), VirtualBaseEnd);
+ auto NonVirtualBaseInits =
+ llvm::make_range(VirtualBaseEnd, NonVirtualBaseEnd);
+ auto MemberInits = llvm::make_range(NonVirtualBaseEnd, AllInits.end());
+
+ // Process virtual base initializers.
+ for (CXXCtorInitializer *Initializer : VirtualBaseInits) {
if (!ConstructVBases)
continue;
SaveAndRestore ThisRAII(CXXThisValue);
if (CGM.getCodeGenOpts().StrictVTablePointers &&
CGM.getCodeGenOpts().OptimizationLevel > 0 &&
- isInitializerOfDynamicClass(*B))
+ isInitializerOfDynamicClass(Initializer))
CXXThisValue = Builder.CreateLaunderInvariantGroup(LoadCXXThis());
- EmitBaseInitializer(*this, ClassDecl, *B);
+ EmitBaseInitializer(*this, ClassDecl, Initializer);
}
if (BaseCtorContinueBB) {
@@ -1314,14 +1332,14 @@ void CodeGenFunction::EmitCtorPrologue(const
CXXConstructorDecl *CD,
}
// Then, non-virtual base initializers.
- for (; B != E && (*B)->isBaseInitializer(); B++) {
- assert(!(*B)->isBaseVirtual());
+ for (CXXCtorInitializer *Initializer : NonVirtualBaseInits) {
+ assert(!Initializer->isBaseVirtual());
SaveAndRestore ThisRAII(CXXThisValue);
if (CGM.getCodeGenOpts().StrictVTablePointers &&
CGM.getCodeGenOpts().OptimizationLevel > 0 &&
- isInitializerOfDynamicClass(*B))
+ isInitializerOfDynamicClass(Initializer))
CXXThisValue = Builder.CreateLaunderInvariantGroup(LoadCXXThis());
- EmitBaseInitializer(*this, ClassDecl, *B);
+ EmitBaseInitializer(*this, ClassDecl, Initializer);
}
InitializeVTablePointers(ClassDecl);
@@ -1329,8 +1347,7 @@ void CodeGenFunction::EmitCtorPrologue(const
CXXConstructorDecl *CD,
// And finally, initialize class members.
FieldConstructionScope FCS(*this, LoadCXXThisAddress());
ConstructorMemcpyizer CM(*this, CD, Args);
- for (; B != E; B++) {
- CXXCtorInitializer *Member = (*B);
+ for (CXXCtorInitializer *Member : MemberInits) {
assert(!Member->isBaseInitializer());
assert(Member->isAnyMemberInitializer() &&
"Delegating initializer on non-delegating constructor");
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