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path: root/llvm/lib/CodeGen/MachineSSAContext.cpp
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2025-03-06[CodeGen] Use Register or MCRegister. NFCCraig Topper
2025-01-24MachineUniformityAnalysis: Improve isConstantOrUndefValuePhi (#112866)Petar Avramovic
Change existing code for G_PHI to match what LLVM-IR version is doing via PHINode::hasConstantOrUndefValue. This is not safe for regular PHI since it may appear with an undef operand and getVRegDef can fail. Most notably this improves number of values that can be allocated to sgpr in AMDGPURegBankSelect. Common case here are phis that appear in structurize-cfg lowering for cycles with multiple exits: Undef incoming value is coming from block that reached cycle exit condition, if other incoming is uniform keep the phi uniform despite the fact it is joining values from pair of blocks that are entered via divergent condition branch.
2023-08-03Restore "[LLVM] move verification of convergence control to a class template""Sameer Sahasrabuddhe
The refactored template can now be used with MachineVerifier. Resubmitted after fixing build errors: - Shared libraries build failed with undefined references due to "extern template" declarations. - Modules build failed due to a cycle dependence between llvm/ADT and llvm/IR. The Generic*Impl.h files should be in llvm/IR to prevent this. Differential Revision: https://reviews.llvm.org/D156522 This restores commit 93a3706711fd46d4d487640d91b16c2eec747c9e. Originally reverted in 466bd9981150906552a1f2308e3c9065bfcb6741.
2023-08-01Revert "[LLVM] move verification of convergence control to a class template"Sameer Sahasrabuddhe
This reverts commit 93a3706711fd46d4d487640d91b16c2eec747c9e. The "extern template" declaration of CycleInfo caused problems in a shared build when CycleInfo was removed from Verifier.cpp. There needs to be an explicit instantiation corresponding to an extern template in every SO.
2023-08-01[LLVM] move verification of convergence control to a class templateSameer Sahasrabuddhe
The refactored template can now be used with MachineVerifier. Reviewed By: arsenm Differential Revision: https://reviews.llvm.org/D156522
2023-07-27[LLVM] refactor GenericSSAContext and its specializationsSameer Sahasrabuddhe
Fix the GenericSSAContext template so that it actually declares all the necessary typenames and the methods that must be implemented by its specializations SSAContext and MachineSSAContext. Reviewed By: arsenm Differential Revision: https://reviews.llvm.org/D156288
2023-07-18[llvm] minor cleanup in GenericSSAContextSameer Sahasrabuddhe
- update comments to reflect actual state - use (implicitly inline) constexpr for a const static member
2023-06-01[CodeGen] Make use of MachineInstr::all_defs and all_uses. NFCI.Jay Foad
Differential Revision: https://reviews.llvm.org/D151424
2023-02-20[llvm][Uniformity] A phi with an undef argument is not always divergentSameer Sahasrabuddhe
The uniformity analysis treated an undef argument to phi to be distinct from any other argument, equivalent to calling PHINode::hasConstantValue() instead of PHINode::hasConstantOrUndefValue(). Such a phi was reported as divergent. This is different from the older divergence analysis which treats such a phi as uniform. Fixed uniformity analysis to match the older behaviour. The original behaviour was added to DivergenceAnalysis in D19013. But it is not clear if relying on the undef value is safe. The defined values are not constant per se; they just happen to be uniform and the non-constant uniform value may not dominate the PHI. Reviewed By: ruiling Differential Revision: https://reviews.llvm.org/D144254
2022-12-20RFC: Uniformity Analysis for Irreducible Control FlowSameer Sahasrabuddhe
Uniformity analysis is a generalization of divergence analysis to include irreducible control flow: 1. The proposed spec presents a notion of "maximal convergence" that captures the existing convention of converging threads at the headers of natual loops. 2. Maximal convergence is then extended to irreducible cycles. The identity of irreducible cycles is determined by the choices made in a depth-first traversal of the control flow graph. Uniformity analysis uses criteria that depend only on closed paths and not cycles, to determine maximal convergence. This makes it a conservative analysis that is independent of the effect of DFS on CycleInfo. 3. The analysis is implemented as a template that can be instantiated for both LLVM IR and Machine IR. Validation: - passes existing tests for divergence analysis - passes new tests with irreducible control flow - passes equivalent tests in MIR and GMIR Based on concepts originally outlined by Nicolai Haehnle <nicolai.haehnle@amd.com> With contributions from Ruiling Song <ruiling.song@amd.com> and Jay Foad <jay.foad@amd.com>. Support for GMIR and lit tests for GMIR/MIR added by Yashwant Singh <yashwant.singh@amd.com>. Differential Revision: https://reviews.llvm.org/D130746
2022-03-16Cleanup codegen includesserge-sans-paille
This is a (fixed) recommit of https://reviews.llvm.org/D121169 after: 1061034926 before: 1063332844 Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup Differential Revision: https://reviews.llvm.org/D121681
2022-03-10Revert "Cleanup codegen includes"Nico Weber
This reverts commit 7f230feeeac8a67b335f52bd2e900a05c6098f20. Breaks CodeGenCUDA/link-device-bitcode.cu in check-clang, and many LLVM tests, see comments on https://reviews.llvm.org/D121169
2022-03-10Cleanup codegen includesserge-sans-paille
after: 1061034926 before: 1063332844 Differential Revision: https://reviews.llvm.org/D121169
2021-12-10Reapply CycleInfo: Introduce cycles as a generalization of loopsSameer Sahasrabuddhe
Reverts 02940d6d2202. Fixes breakage in the modules build. LLVM loops cannot represent irreducible structures in the CFG. This change introduce the concept of cycles as a generalization of loops, along with a CycleInfo analysis that discovers a nested hierarchy of such cycles. This is based on Havlak (1997), Nesting of Reducible and Irreducible Loops. The cycle analysis is implemented as a generic template and then instatiated for LLVM IR and Machine IR. The template relies on a new GenericSSAContext template which must be specialized when used for each IR. This review is a restart of an older review request: https://reviews.llvm.org/D83094 Original implementation by Nicolai Hähnle <nicolai.haehnle@amd.com>, with recent refactoring by Sameer Sahasrabuddhe <sameer.sahasrabuddhe@amd.com> Differential Revision: https://reviews.llvm.org/D112696
2021-12-07Revert "CycleInfo: Introduce cycles as a generalization of loops"Jonas Devlieghere
This reverts commit 0fe61ecc2cef333250a152cd90d80d0b802b27db because it breaks the modules build. https://green.lab.llvm.org/green/job/clang-stage2-rthinlto/4858/ https://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake/39112/
2021-12-07CycleInfo: Introduce cycles as a generalization of loopsSameer Sahasrabuddhe
LLVM loops cannot represent irreducible structures in the CFG. This change introduce the concept of cycles as a generalization of loops, along with a CycleInfo analysis that discovers a nested hierarchy of such cycles. This is based on Havlak (1997), Nesting of Reducible and Irreducible Loops. The cycle analysis is implemented as a generic template and then instatiated for LLVM IR and Machine IR. The template relies on a new GenericSSAContext template which must be specialized when used for each IR. This review is a restart of an older review request: https://reviews.llvm.org/D83094 Original implementation by Nicolai Hähnle <nicolai.haehnle@amd.com>, with recent refactoring by Sameer Sahasrabuddhe <sameer.sahasrabuddhe@amd.com> Differential Revision: https://reviews.llvm.org/D112696
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