The TBAA nodes hang off a root node. So we create that next: llvm::MDNode *tbaa_root; // Do what Clang does tbaa_root = mdbuilder.createTBAARoot("Simple C / C++ TBAA");

Check the first operand of the tbaa tag node, if it is a MDNode, we treat it as struct-path aware TBA...

December 12, 2024 - I'm currently working on implementing support for TBAA ( llvm/clangir#1076 ) in Clang IR and have noticed that the LLVM Dialect does not accommodate the new format of TBAA. To address this, I’v...

There are 2 pending PRs with bug fixes for special cases uncovered during some of my testing: * llvm#116991 * llvm#116596 ... Support for more precise TBAA metadata has been added a while ago (behind the -fpointer-tbaa flag). The more precise TBAA metadata allows treating accesses of different pointer types as no-alias.

April 18, 2024 - Hello, this question is bit between topics of MLIR and LLVM, but since’ I’m working with MLIR currently, I set the category to ‘MLIR’. I’m working on my own dialect that can be lowered directly to MLIR LLVM dialect, and I want to attach TBAA metadata to help LLVM compiler optimize the code with type aliases.

LLVM's Alias Anslysis API · Location, Location, Location · Pointer · Size · TBAA tag · Sizes are given in address units (bytes usually) alias · - 2 Locations · getModRefInfo and getModRefBehavior · pointsToConstantMemory · AliasAnalysis.h basics · NoAlias = can reorder* MustAlias ...

At EuroLLVM, Chandler and I chatted about the design for a potential TBAA sanitizer. Here's my attempt to summarize: C/C++ have type-based aliasing rules, and LLVM's optimizer can exploit these given TBAA metadata added by Clang. Roughly, a pointer of given type cannot be used to access an ...

June 15, 2024 - struct Wrapper { int t; }; struct T { Wrapper a, b; }; void g(T& t1, const T& t2 ) { t1.a = t2.a; t1.b = t2.b; } Up until clang 17, -new-struct-path-tbaa used to be able to deduce that t1.a and t2.b do not alias. in clang 18 it no longer...

March 22, 2022 - The simplicity, speed, and accuracy of TBAA has allowed it to stick around in many modern compilers. LLVM has several different alias analyses, including an implementation of TBAA. The compiler frontend must include type annotations that can then be used for alias based optimization within ...

March 28, 2022 - This patch extends Clang's TBAA generation code to emit distinct tags for incompatible pointer types · Pointers with different element types are incompatible if the pointee types are also incompatible (modulo sugar/modifiers)

May 3, 2023 - -new-struct-path-tbaa is work from ~6Y ago (although I think the discussion started ~10Y ago ) authored by @kosarev with fixes from ~1Y ago by @brunodf. It creates !tbaa metadata for structs and members where it wasn’t available before - in particular improving the optimizations for strong-typedefs, making them essentially zero-cost abstractions as they are advertised to be.

April 23, 2020 - // http://llvm.org/docs/AliasAnalysis.html#OtherItfs). // // With struct-path aware TBAA, the MDNodes attached to an instruction using · // "!tbaa" are called path tag nodes. // // The path tag node has 4 fields with the last field being optional.

Visit an instruction, or a TBAA node itself as part of a metadata, and return true if it is valid, return false if an invalid TBAA is attached. Definition at line 8189 of file Verifier.cpp. References CheckTBAA, llvm::dyn_cast_or_null(), llvm::mdconst::dyn_extract_or_null(), llvm::MDNode::getNumOperands(), llvm::MDNode::getOperand(), I, llvm::SmallPtrSetImpl< PtrType >::insert(), llvm::Invalid, llvm::isa(), isNewFormatTBAATypeNode(), IsRootTBAANode(), and llvm::Offset.

April 23, 2020 - // RUN: %clang_cc1 -triple x86_64-apple-darwin -O1 -no-struct-path-tbaa -disable-llvm-passes %s -emit-llvm -o - | FileCheck %s

March 12, 2025 - TBAAType-Based Alias Analysis / Strict AliasingType-Based Alias Analysis / Strict Aliasingclang:codegenIR generation bugs: mangling, exceptions, etc.IR generation bugs: mangling, exceptions, etc.missed-optimization

June 7, 2024 - Type Based Alias Analysis emits metadata nodes in the frontend, and an analysis pass in the middle-end does access tag matching to determine if two pointers alias or not. TBAA metadata is only attached to Load and Store Instructions.

The language C has several constraints which allow compiler vendors to implement optimizations in order to emit fast code. One of such an optimization is based on type-based alias analysis (TBAA for short) which itself makes use of the strict aliasing rules. Aliasing refers to the property ...

January 18, 2026 - I’ve just posted the PR: LLVM, Coroutines: Introduce TBAA metadata for frame object by yonillasky · Pull Request #176543 · llvm/llvm-project · GitHub To demonstrate why this is a problem, I can show a simple C++ coroutine “benchmark” example, where the lack of TBAA prevents “reloads” from being hoisted out of a tight loop.