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2024-10-14[NewPM][CodeGen] Port StackColoring to NPM (#111812)Akshat Oke1-1/+1
2024-09-04[CodeGen][NewPM] Port MachineCSE pass to new pass manager. (#106605)Christudasan Devadasan1-1/+1
2024-08-29[ExtendLifetimes] Implement llvm.fake.use to extend variable lifetimes (#86149)Stephen Tozer1-0/+1
This patch is part of a set of patches that add an `-fextend-lifetimes` flag to clang, which extends the lifetimes of local variables and parameters for improved debuggability. In addition to that flag, the patch series adds a pragma to selectively disable `-fextend-lifetimes`, and an `-fextend-this-ptr` flag which functions as `-fextend-lifetimes` for this pointers only. All changes and tests in these patches were written by Wolfgang Pieb (@wolfy1961), while Stephen Tozer (@SLTozer) has handled review and merging. The extend lifetimes flag is intended to eventually be set on by `-Og`, as discussed in the RFC here: https://discourse.llvm.org/t/rfc-redefine-og-o1-and-add-a-new-level-of-og/72850 This patch implements a new intrinsic instruction in LLVM, `llvm.fake.use` in IR and `FAKE_USE` in MIR, that takes a single operand and has no effect other than "using" its operand, to ensure that its operand remains live until after the fake use. This patch does not emit fake uses anywhere; the next patch in this sequence causes them to be emitted from the clang frontend, such that for each variable (or this) a fake.use operand is inserted at the end of that variable's scope, using that variable's value. This patch covers everything post-frontend, which is largely just the basic plumbing for a new intrinsic/instruction, along with a few steps to preserve the fake uses through optimizations (such as moving them ahead of a tail call or translating them through SROA). Co-authored-by: Stephen Tozer <stephen.tozer@sony.com>
2024-07-15[CodeGen] Port `two-address-instructions` to new pass manager (#98632)paperchalice1-1/+1
Add `TwoAddressInstructionPass`.
2024-07-15[CodeGen][NewPM] Port `MachineVerifier` to new pass manager (#98628)paperchalice1-1/+1
- Add `MachineVerifierPass`. - Use complete `MachineVerifierPass` in `VerifyInstrumentation` if possible. `LiveStacksAnalysis` will be added in future, all other analyses are done.
2024-07-12[CodeGen][NewPM] Port `machine-block-freq` to new pass manager (#98317)paperchalice1-1/+1
- Add `MachineBlockFrequencyAnalysis`. - Add `MachineBlockFrequencyPrinterPass`. - Use `MachineBlockFrequencyInfoWrapperPass` in legacy pass manager. - `LazyMachineBlockFrequencyInfo::print` is empty, drop it due to new pass manager migration.
2024-07-10[CodeGen][NewPM] Port `LiveIntervals` to new pass manager (#98118)paperchalice1-1/+1
- Add `LiveIntervalsAnalysis`. - Add `LiveIntervalsPrinterPass`. - Use `LiveIntervalsWrapperPass` in legacy pass manager. - Use `std::unique_ptr` instead of raw pointer for `LICalc`, so destructor and default move constructor can handle it correctly. This would be the last analysis required by `PHIElimination`.
2024-07-09[CodeGen][NewPM] Port `SlotIndexes` to new pass manager (#97941)paperchalice1-1/+1
- Add `SlotIndexesAnalysis`. - Add `SlotIndexesPrinterPass`. - Use `SlotIndexesWrapperPass` in legacy pass.
2024-07-09[CodeGen][NewPM] Port `LiveVariables` to new pass manager (#97880)paperchalice1-1/+1
- Port `LiveVariables` to new pass manager. - Convert to `LiveVariablesWrapperPass` in legacy pass manager.
2024-07-09[CodeGen][NewPM] Port `machine-loops` to new pass manager (#97793)paperchalice1-1/+1
- Add `MachineLoopAnalysis`. - Add `MachineLoopPrinterPass`. - Convert to `MachineLoopInfoWrapperPass` in legacy pass manager.
2024-06-12[CodeGen][NewPM] Split `MachinePostDominators` into a concrete analysis ↵paperchalice1-1/+1
result (#95113) `MachinePostDominators` version of #94571.
2024-06-11[CodeGen][NewPM] Split `MachineDominatorTree` into a concrete analysis ↵paperchalice1-1/+1
result (#94571) Prepare for new pass manager version of `MachineDominatorTreeAnalysis`. We may need a machine dominator tree version of `DomTreeUpdater` to handle `SplitCriticalEdge` in some CodeGen passes.
2024-02-26[CodeGen] [ARM] Make RISC-V Init Undef Pass Target Independent and add ↵Jack Styles1-0/+1
support for the ARM Architecture. (#77770) When using Greedy Register Allocation, there are times where early-clobber values are ignored, and assigned the same register. This is illeagal behaviour for these intructions. To get around this, using Pseudo instructions for early-clobber registers gives them a definition and allows Greedy to assign them to a different register. This then meets the ARM Architecture Reference Manual and matches the defined behaviour. This patch takes the existing RISC-V patch and makes it target independent, then adds support for the ARM Architecture. Doing this will ensure early-clobber restraints are followed when using the ARM Architecture. Making the pass target independent will also open up possibility that support other architectures can be added in the future.
2024-02-25[CodeGen] Port AtomicExpand to new Pass Manager (#71220)Rishabh Bali1-1/+1
Port the `atomicexpand` pass to the new Pass Manager. Fixes #64559
2024-01-09Port CodeGenPrepare to new pass manager (and BasicBlockSectionsProfil… ↵Nick Anderson1-1/+1
(#77182) Port CodeGenPrepare to new pass manager and dependency BasicBlockSectionsProfileReader Fixes: #75380 Co-authored-by: Krishna-13-cyber <84722531+Krishna-13-cyber@users.noreply.github.com>
2024-01-05Revert 4d7c5ad58467502fcbc433591edff40d8a4d697d "[NewPM] Update ↵Simon Pilgrim1-1/+1
CodeGenPreparePass reference in CodeGenPassBuilder (#77054)" Revert e0c554ad87d18dcbfcb9b6485d0da800ae1338d1 "Port CodeGenPrepare to new pass manager (and BasicBlockSectionsProfil… (#75380)" Revert #75380 and #77054 as they were breaking EXPENSIVE_CHECKS buildbots: https://lab.llvm.org/buildbot/#/builders/104
2024-01-05Port CodeGenPrepare to new pass manager (and BasicBlockSectionsProfil… ↵Nick Anderson1-1/+1
(#75380) Port CodeGenPrepare to new pass manager and dependency BasicBlockSectionsProfileReader Fixes: #64560 Co-authored-by: Krishna-13-cyber <84722531+Krishna-13-cyber@users.noreply.github.com>
2023-12-13[CodeGen] Port `ExpandMemCmp` to new pass manager (#74050)paperchalice1-1/+1
2023-12-13[CodeGen] Port `IndirectBrExpand` to new pass manager (#75287)paperchalice1-1/+1
2023-10-27[BasicBlockSections] Apply path cloning with -basic-block-sections. (#68860)Rahman Lavaee1-0/+1
https://github.com/llvm/llvm-project/commit/28b912687900bc0a67cd61c374fce296b09963c4 introduced the path cloning format in the basic-block-sections profile. This PR validates and applies path clonings. A path cloning is valid if all of these conditions hold: 1. All bb ids in the path are mapped to existing blocks. 2. Each two consecutive bb ids in the path have a successor relationship in the CFG. 3. The path does not include a block with indirect branches, except possibly as the last block. Applying a path cloning involves cloning all blocks in the path (except the first one) and setting up their branches. Once all clonings are applied, the cluster information is used to guide block layout in the modified function.
2023-04-21[BreakFalseDeps] Respect dead blocks.Serguei Katkov1-0/+1
The pass uses ReachingDefAnalysis which has no information about instructions in dead blocks. So do not process them. Reviewed By: pengfei Differential Revision: https://reviews.llvm.org/D148329
2023-04-14[llvm-c] Remove PassRegistry and initialization APIsNikita Popov1-5/+0
Remove C APIs for interacting with PassRegistry and pass initialization. These are legacy PM concepts, and are no longer relevant for the new pass manager. Calls to these initialization functions can simply be dropped. Differential Revision: https://reviews.llvm.org/D145043
2023-02-16[llvm] boilerplate for new callbrprepare codegen IR passNick Desaulniers1-0/+1
Because this pass is to be a codegen pass, it must use the legacy pass manager. Link: https://discourse.llvm.org/t/rfc-syncing-asm-goto-with-outputs-with-gcc/65453/8 Reviewed By: aeubanks, void Differential Revision: https://reviews.llvm.org/D139861
2023-02-13[HardwareLoops] NewPM support.Samuel Parker1-1/+1
With the NPM, we're now defaulting to preserving LCSSA, so a couple of tests have changed slightly. Differential Revision: https://reviews.llvm.org/D140982
2023-01-19[codegen] Add StackFrameLayoutAnalysisPassPaul Kirth1-0/+1
Issue #58168 describes the difficulty diagnosing stack size issues identified by -Wframe-larger-than. For simple code, its easy to understand the stack layout and where space is being allocated, but in more complex programs, where code may be heavily inlined, unrolled, and have duplicated code paths, it is no longer easy to manually inspect the source program and understand where stack space can be attributed. This patch implements a machine function pass that emits remarks with a textual representation of stack slots, and also outputs any available debug information to map source variables to those slots. The new behavior can be used by adding `-Rpass-analysis=stack-frame-layout` to the compiler invocation. Like other remarks the diagnostic information can be saved to a file in a machine readable format by adding -fsave-optimzation-record. Fixes: #58168 Reviewed By: nickdesaulniers, thegameg Differential Revision: https://reviews.llvm.org/D135488
2023-01-13Revert "[codegen] Add StackFrameLayoutAnalysisPass"Paul Kirth1-1/+0
This breaks on some AArch64 bots This reverts commit 0a652c540556a118bbd9386ed3ab7fd9e60a9754.
2023-01-13[codegen] Add StackFrameLayoutAnalysisPassPaul Kirth1-0/+1
Issue #58168 describes the difficulty diagnosing stack size issues identified by -Wframe-larger-than. For simple code, its easy to understand the stack layout and where space is being allocated, but in more complex programs, where code may be heavily inlined, unrolled, and have duplicated code paths, it is no longer easy to manually inspect the source program and understand where stack space can be attributed. This patch implements a machine function pass that emits remarks with a textual representation of stack slots, and also outputs any available debug information to map source variables to those slots. The new behavior can be used by adding `-Rpass-analysis=stack-frame-layout` to the compiler invocation. Like other remarks the diagnostic information can be saved to a file in a machine readable format by adding -fsave-optimzation-record. Fixes: #58168 Reviewed By: nickdesaulniers, thegameg Differential Revision: https://reviews.llvm.org/D135488
2023-01-03[TypePromotion] NewPM support.Samuel Parker1-1/+1
Differential Revision: https://reviews.llvm.org/D140893
2022-12-20RFC: Uniformity Analysis for Irreducible Control FlowSameer Sahasrabuddhe1-0/+2
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
2022-12-09[Assignment Tracking][Analysis] Add analysis passOCHyams1-0/+1
The Assignment Tracking debug-info feature is outlined in this RFC: https://discourse.llvm.org/t/ rfc-assignment-tracking-a-better-way-of-specifying-variable-locations-in-ir Add initial revision of assignment tracking analysis pass --------------------------------------------------------- This patch squashes five individually reviewed patches into one: #1 https://reviews.llvm.org/D136320 #2 https://reviews.llvm.org/D136321 #3 https://reviews.llvm.org/D136325 #4 https://reviews.llvm.org/D136331 #5 https://reviews.llvm.org/D136335 Patch #1 introduces 2 new files: AssignmentTrackingAnalysis.h and .cpp. The two subsequent patches modify those files only. Patch #4 plumbs the analysis into SelectionDAG, and patch #5 is a collection of tests for the analysis as a whole. The analysis was broken up into smaller chunks for review purposes but for the most part the tests were written using the whole analysis. It would be possible to break up the tests for patches #1 through #3 for the purpose of landing the patches seperately. However, most them would require an update for each patch. In addition, patch #4 - which connects the analysis to SelectionDAG - is required by all of the tests. If there is build-bot trouble, we might try a different landing sequence. Analysis problem and goal ------------------------- Variables values can be stored in memory, or available as SSA values, or both. Using the Assignment Tracking metadata, it's not possible to determine a variable location just by looking at a debug intrinsic in isolation. Instructions without any metadata can change the location of a variable. The meaning of dbg.assign intrinsics changes depending on whether there are linked instructions, and where they are relative to those instructions. So we need to analyse the IR and convert the embedded information into a form that SelectionDAG can consume to produce debug variable locations in MIR. The solution is a dataflow analysis which, aiming to maximise the memory location coverage for variables, outputs a mapping of instruction positions to variable location definitions. API usage --------- The analysis is named `AssignmentTrackingAnalysis`. It is added as a required pass for SelectionDAGISel when assignment tracking is enabled. The results of the analysis are exposed via `getResults` using the returned `const FunctionVarLocs *`'s const methods: const VarLocInfo *single_locs_begin() const; const VarLocInfo *single_locs_end() const; const VarLocInfo *locs_begin(const Instruction *Before) const; const VarLocInfo *locs_end(const Instruction *Before) const; void print(raw_ostream &OS, const Function &Fn) const; Debug intrinsics can be ignored after running the analysis. Instead, variable location definitions that occur between an instruction `Inst` and its predecessor (or block start) can be found by looping over the range: locs_begin(Inst), locs_end(Inst) Similarly, variables with a memory location that is valid for their lifetime can be iterated over using the range: single_locs_begin(), single_locs_end() Further detail -------------- For an explanation of the dataflow implementation and the integration with SelectionDAG, please see the reviews linked at the top of this commit message. Reviewed By: jmorse
2022-12-05Reapply "[CodeGen] Add new pass for late cleanup of redundant definitions."Jonas Paulsson1-0/+1
This reverts commit 122efef8ee9be57055d204d52c38700fe933c033. - Patch fixed to not reuse definitions from predecessors in EH landing pads. - Late review suggestions (by MaskRay) have been addressed. - M68k/pipeline.ll test updated. - Init captures added in processBlock() to avoid capturing structured bindings. - RISCV has this disabled for now. Original commit message: A new pass MachineLateInstrsCleanup is added to be run after PEI. This is a simple pass that removes redundant and identical instructions whenever found by scanning the MF once while keeping track of register definitions in a map. These instructions are typically immediate loads resulting from rematerialization, and address loads emitted by target in eliminateFrameInde(). This is enabled by default, but a target could easily disable it by means of 'disablePass(&MachineLateInstrsCleanupID);'. This late cleanup is naturally not "optimal" in removing instructions as it is done by looking at phys-regs, but still quite effective. It would be desirable to improve other parts of CodeGen and avoid these redundant instructions in the first place, but there are no ideas for this yet. Differential Revision: https://reviews.llvm.org/D123394 Reviewed By: RKSimon, foad, craig.topper, arsenm, asb
2022-12-05Use-after-return sanitizer binary metadataDmitry Vyukov1-0/+1
Currently per-function metadata consists of: (start-pc, size, features) This adds a new UAR feature and if it's set an additional element: (start-pc, size, features, stack-args-size) Reviewed By: melver Differential Revision: https://reviews.llvm.org/D136078
2022-12-05Revert "Reapply "[CodeGen] Add new pass for late cleanup of redundant ↵Jonas Paulsson1-1/+0
definitions."" This reverts commit 17db0de330f943833296ae72e26fa988bba39cb3. Some more bots got broken - need to investigate.
2022-12-03Reapply "[CodeGen] Add new pass for late cleanup of redundant definitions."Jonas Paulsson1-0/+1
Init captures added in processBlock() to avoid capturing structured bindings, which caused the build problems (with clang). RISCV has this disabled for now until problems relating to post RA pseudo expansions are resolved.
2022-12-01Revert "[CodeGen] Add new pass for late cleanup of redundant definitions."Jonas Paulsson1-1/+0
Temporarily revert and fix buildbot failure. This reverts commit 6d12599fd4134c1da63198c74a25490d28c733f6.
2022-12-01[CodeGen] Add new pass for late cleanup of redundant definitions.Jonas Paulsson1-0/+1
A new pass MachineLateInstrsCleanup is added to be run after PEI. This is a simple pass that removes redundant and identical instructions whenever found by scanning the MF once while keeping track of register definitions in a map. These instructions are typically immediate loads resulting from rematerialization, and address loads emitted by target in eliminateFrameInde(). This is enabled by default, but a target could easily disable it by means of 'disablePass(&MachineLateInstrsCleanupID);'. This late cleanup is naturally not "optimal" in removing instructions as it is done by looking at phys-regs, but still quite effective. It would be desirable to improve other parts of CodeGen and avoid these redundant instructions in the first place, but there are no ideas for this yet. Differential Revision: https://reviews.llvm.org/D123394 Reviewed By: RKSimon, foad, craig.topper, arsenm, asb
2022-12-01[X86] Add ExpandLargeFpConvert Pass and enable for X86Freddy Ye1-0/+1
As stated in https://discourse.llvm.org/t/rfc-llc-add-expandlargeintfpconvert-pass-for-fp-int-conversion-of-large-bitint/65528, this implementation is very similar to ExpandLargeDivRem, which expands ‘fptoui .. to’, ‘fptosi .. to’, ‘uitofp .. to’, ‘sitofp .. to’ instructions with a bitwidth above a threshold into auto-generated functions. This is useful for targets like x86_64 that cannot lower fp convertions with more than 128 bits. The expanded nodes are referring from the IR generated by `compiler-rt/lib/builtins/floattidf.c`, `compiler-rt/lib/builtins/fixdfti.c`, and etc. Corner cases: 1. For fp16: as there is no related builtins added in compliler-rt. So I mainly utilized the fp32 <-> fp16 lib calls to implement. 2. For fp80: as this pass is soft fp emulation and no fp80 instructions can help in this problem. I recommend users to deprecate this usage. For now, the implementation uses fp128 as the temporary conversion type and inserts fptrunc/ext at top/end of the function. 3. For bf16: as clang FE currently doesn't support bf16 algorithm operations (convert to int, float, +, -, *, ...), this patch doesn't consider bf16 for now. 4. For unsigned FPToI: since both default hardware behaviors and libgcc are ignoring "returns 0 for negative input" spec. This pass follows this old way to ignore unsigned FPToI. See this example: https://gcc.godbolt.org/z/bnv3jqW1M The end-to-end tests are uploaded at https://reviews.llvm.org/D138261 Reviewed By: LuoYuanke, mgehre-amd Differential Revision: https://reviews.llvm.org/D137241
2022-11-30Revert "Use-after-return sanitizer binary metadata"Marco Elver1-1/+0
This reverts commit d3c851d3fc8b69dda70bf5f999c5b39dc314dd73. Some bots broke: - https://luci-milo.appspot.com/ui/p/fuchsia/builders/toolchain.ci/clang-linux-x64/b8796062278266465473/overview - https://lab.llvm.org/buildbot/#/builders/124/builds/5759/steps/7/logs/stdio
2022-11-30Use-after-return sanitizer binary metadataDmitry Vyukov1-0/+1
Currently per-function metadata consists of: (start-pc, size, features) This adds a new UAR feature and if it's set an additional element: (start-pc, size, features, stack-args-size) Reviewed By: melver Differential Revision: https://reviews.llvm.org/D136078
2022-11-30Revert "Use-after-return sanitizer binary metadata"Dmitry Vyukov1-1/+0
This reverts commit e6aea4a5db09c845276ece92737a6aac97794100. Broke tests: https://lab.llvm.org/buildbot/#/builders/16/builds/38992
2022-11-30Use-after-return sanitizer binary metadataDmitry Vyukov1-0/+1
Currently per-function metadata consists of: (start-pc, size, features) This adds a new UAR feature and if it's set an additional element: (start-pc, size, features, stack-args-size) Reviewed By: melver Differential Revision: https://reviews.llvm.org/D136078
2022-11-29Revert "Use-after-return sanitizer binary metadata"Kazu Hirata1-1/+0
This reverts commit a1255dc467f7ce57a966efa76bbbb4ee91d9115a. This patch results in: llvm/lib/CodeGen/SanitizerBinaryMetadata.cpp:57:17: error: no member named 'size' in 'llvm::MDTuple'
2022-11-29Use-after-return sanitizer binary metadataDmitry Vyukov1-0/+1
Currently per-function metadata consists of: (start-pc, size, features) This adds a new UAR feature and if it's set an additional element: (start-pc, size, features, stack-args-size) Reviewed By: melver Differential Revision: https://reviews.llvm.org/D136078
2022-10-21[ObjCARC] Remove legacy PM versions of optimization passesArthur Eubanks1-0/+1
This doesn't touch objc-arc-contract because that's in the codegen pipeline. However, this does move its corresponding initialize function into initializeCodegen(). Reviewed By: asbirlea Differential Revision: https://reviews.llvm.org/D135041
2022-09-22-dot-machine-cfg for printing MachineFunction to a dot fileChristudasan Devadasan1-0/+1
This pass allows a user to dump a MIR function to a dot file and view it as a graph. It is targeted to provide a similar functionality as -dot-cfg pass on LLVM-IR. As of now the pass also support below flags: -dot-mcfg-only [optional][won't print instructions in the graph just block name] -mcfg-dot-filename-prefix [optional][prefix to add to output dot file] -mcfg-func-name [optional] [specify function name or it's substring, handy if mir file contains multiple functions and you need to see graph of just one] More flags and details can be introduced as per the requirements in future. This pass is inspired from -dot-cfg IR pass and APIs are written in almost identical format. Patch by Yashwant Singh <Yashwant.Singh@amd.com> (yassingh) Reviewed By: arsenm Differential Revision: https://reviews.llvm.org/D133709
2022-08-26[llvm/CodeGen] Add ExpandLargeDivRem passMatthias Gehre1-0/+1
Adds a pass ExpandLargeDivRem to expand div/rem instructions with more than 128 bits into a loop computing that value. As discussed on https://reviews.llvm.org/D120327, this approach has the advantage that it is independent of the runtime library. This also helps the clang driver, which otherwise would need to understand enough about the runtime library to know whether to allow _BitInts with more than 128 bits. Targets are still free to disable this pass and instead provide a faster implementation in a runtime library. Fixes https://github.com/llvm/llvm-project/issues/44994 Differential Revision: https://reviews.llvm.org/D126644
2022-05-19[SelectOpti][1/5] Setup new select-optimize passSotiris Apostolakis1-0/+1
This is the first commit for the cmov-vs-branch optimization pass. The goal is to develop a new profile-guided and target-independent cost/benefit analysis for selecting conditional moves over branches when optimizing for performance. Initially, this new pass is expected to be enabled only for instrumentation-based PGO. RFC: https://discourse.llvm.org/t/rfc-cmov-vs-branch-optimization/6040 Reviewed By: tejohnson Differential Revision: https://reviews.llvm.org/D120230
2022-04-11[CodeGen] Async unwind - add a pass to fix CFI informationMomchil Velikov1-0/+1
This pass inserts the necessary CFI instructions to compensate for the inconsistency of the call-frame information caused by linear (non-CGA aware) nature of the unwind tables. Unlike the `CFIInstrInserer` pass, this one almost always emits only `.cfi_remember_state`/`.cfi_restore_state`, which results in smaller unwind tables and also transparently handles custom unwind info extensions like CFA offset adjustement and save locations of SVE registers. This pass takes advantage of the constraints taht LLVM imposes on the placement of save/restore points (cf. `ShrinkWrap.cpp`): * there is a single basic block, containing the function prologue * possibly multiple epilogue blocks, where each epilogue block is complete and self-contained, i.e. CSR restore instructions (and the corresponding CFI instructions are not split across two or more blocks. * prologue and epilogue blocks are outside of any loops Thus, during execution, at the beginning and at the end of each basic block the function can be in one of two states: - "has a call frame", if the function has executed the prologue, or has not executed any epilogue - "does not have a call frame", if the function has not executed the prologue, or has executed an epilogue These properties can be computed for each basic block by a single RPO traversal. From the point of view of the unwind tables, the "has/does not have call frame" state at beginning of each block is determined by the state at the end of the previous block, in layout order. Where these states differ, we insert compensating CFI instructions, which come in two flavours: - CFI instructions, which reset the unwind table state to the initial one. This is done by a target specific hook and is expected to be trivial to implement, for example it could be: ``` .cfi_def_cfa <sp>, 0 .cfi_same_value <rN> .cfi_same_value <rN-1> ... ``` where `<rN>` are the callee-saved registers. - CFI instructions, which reset the unwind table state to the one created by the function prologue. These are the sequence: ``` .cfi_restore_state .cfi_remember_state ``` In this case we also insert a `.cfi_remember_state` after the last CFI instruction in the function prologue. Reviewed By: MaskRay, danielkiss, chill Differential Revision: https://reviews.llvm.org/D114545
2022-04-05Revert "[CodeGen] Async unwind - add a pass to fix CFI information"Muhammad Omair Javaid1-1/+0
This reverts commit 980c3e6dd223a8e628367144b8180117950bb364. This commit had failing tests with clang crashing across various AArch64/Linux buildots. https://lab.llvm.org/buildbot/#/builders/179/builds/3346 Differential Revision: https://reviews.llvm.org/D114545
2022-04-04[CodeGen] Async unwind - add a pass to fix CFI informationMomchil Velikov1-0/+1
This pass inserts the necessary CFI instructions to compensate for the inconsistency of the call-frame information caused by linear (non-CFG aware) nature of the unwind tables. Unlike the `CFIInstrInserer` pass, this one almost always emits only `.cfi_remember_state`/`.cfi_restore_state`, which results in smaller unwind tables and also transparently handles custom unwind info extensions like CFA offset adjustement and save locations of SVE registers. This pass takes advantage of the constraints that LLVM imposes on the placement of save/restore points (cf. `ShrinkWrap.cpp`): * there is a single basic block, containing the function prologue * possibly multiple epilogue blocks, where each epilogue block is complete and self-contained, i.e. CSR restore instructions (and the corresponding CFI instructions are not split across two or more blocks. * prologue and epilogue blocks are outside of any loops Thus, during execution, at the beginning and at the end of each basic block the function can be in one of two states: - "has a call frame", if the function has executed the prologue, or has not executed any epilogue - "does not have a call frame", if the function has not executed the prologue, or has executed an epilogue These properties can be computed for each basic block by a single RPO traversal. In order to accommodate backends which do not generate unwind info in epilogues we compute an additional property "strong no call frame on entry" which is set for the entry point of the function and for every block reachable from the entry along a path that does not execute the prologue. If this property holds, it takes precedence over the "has a call frame" property. From the point of view of the unwind tables, the "has/does not have call frame" state at beginning of each block is determined by the state at the end of the previous block, in layout order. Where these states differ, we insert compensating CFI instructions, which come in two flavours: - CFI instructions, which reset the unwind table state to the initial one. This is done by a target specific hook and is expected to be trivial to implement, for example it could be: ``` .cfi_def_cfa <sp>, 0 .cfi_same_value <rN> .cfi_same_value <rN-1> ... ``` where `<rN>` are the callee-saved registers. - CFI instructions, which reset the unwind table state to the one created by the function prologue. These are the sequence: ``` .cfi_restore_state .cfi_remember_state ``` In this case we also insert a `.cfi_remember_state` after the last CFI instruction in the function prologue. Reviewed By: MaskRay, danielkiss, chill Differential Revision: https://reviews.llvm.org/D114545