Enum Passes

#[repr(C)]
pub enum Passes {
    AggressiveDCE = 0,
    AmdExtToKhr = 1,
    BlockMerge = 2,
    ConditionalConstantPropagation = 3,
    CFGCleanup = 4,
    CodeSinking = 5,
    CombineAccessChains = 6,
    CompactIds = 7,
    ConvertRelaxedToHalf = 8,
    CopyPropagateArrays = 9,
    DeadBranchElim = 10,
    DeadInsertElim = 11,
    DeadVariableElimination = 12,
    DescriptorScalarReplacement = 13,
    EliminateDeadConstant = 14,
    EliminateDeadFunctions = 15,
    EliminateDeadMembers = 16,
    FixStorageClass = 17,
    FlattenDecoration = 18,
    FoldSpecConstantOpAndComposite = 19,
    FreezeSpecConstantValue = 20,
    GraphicsRobustAccess = 21,
    IfConversion = 22,
    InlineExhaustive = 23,
    InlineOpaque = 24,
    InsertExtractElim = 25,
    InterpolateFixup = 26,
    LocalAccessChainConvert = 27,
    LocalMultiStoreElim = 28,
    LocalRedundancyElimination = 29,
    LocalSingleBlockLoadStoreElim = 30,
    LocalSingleStoreElim = 31,
    LoopInvariantCodeMotion = 32,
    LoopPeeling = 33,
    LoopUnswitch = 34,
    MergeReturn = 35,
    Null = 36,
    PrivateToLocal = 37,
    PropagateLineInfo = 38,
    ReduceLoadSize = 39,
    RedundancyElimination = 40,
    RedundantLineInfoElim = 41,
    RelaxFloatOps = 42,
    RemoveDuplicates = 43,
    RemoveUnusedInterfaceVariables = 44,
    ReplaceInvalidOpcode = 45,
    Simplification = 46,
    SSARewrite = 47,
    StrengthReduction = 48,
    StripDebugInfo = 49,
    StripNonSemanticInfo = 50,
    UnifyConstant = 51,
    UpgradeMemoryModel = 52,
    VectorDCE = 53,
    Workaround1209 = 54,
    WrapOpKill = 55,
}

Variants

AggressiveDCE = 0

Create aggressive dead code elimination pass This pass eliminates unused code from the module. In addition, it detects and eliminates code which may have spurious uses but which do not contribute to the output of the function. The most common cause of such code sequences is summations in loops whose result is no longer used due to dead code elimination. This optimization has additional compile time cost over standard dead code elimination.

This pass only processes entry point functions. It also only processes shaders with relaxed logical addressing (see opt/instruction.h). It currently will not process functions with function calls. Unreachable functions are deleted.

This pass will be made more effective by first running passes that remove dead control flow and inlines function calls.

This pass can be especially useful after running Local Access Chain Conversion, which tends to cause cycles of dead code to be left after Store/Load elimination passes are completed. These cycles cannot be eliminated with standard dead code elimination.

AmdExtToKhr = 1

Replaces the extensions VK_AMD_shader_ballot,VK_AMD_gcn_shader, and VK_AMD_shader_trinary_minmax with equivalent code using core instructions and capabilities.

BlockMerge = 2

Creates a block merge pass. This pass searches for blocks with a single Branch to a block with no other predecessors and merges the blocks into a single block. Continue blocks and Merge blocks are not candidates for the second block.

The pass is most useful after Dead Branch Elimination, which can leave such sequences of blocks. Merging them makes subsequent passes more effective, such as single block local store-load elimination.

While this pass reduces the number of occurrences of this sequence, at this time it does not guarantee all such sequences are eliminated.

Presence of phi instructions can inhibit this optimization. Handling these is left for future improvements.

ConditionalConstantPropagation = 3

Creates a conditional constant propagation (CCP) pass. This pass implements the SSA-CCP algorithm in

 Constant propagation with conditional branches,
 Wegman and Zadeck, ACM TOPLAS 13(2):181-210.

Constant values in expressions and conditional jumps are folded and simplified. This may reduce code size by removing never executed jump targets and computations with constant operands.

CFGCleanup = 4

Creates a CFG cleanup pass. This pass removes cruft from the control flow graph of functions that are reachable from entry points and exported functions. It currently includes the following functionality:

• Removal of unreachable basic blocks.

CodeSinking = 5

Create a pass to do code sinking. Code sinking is a transformation where an instruction is moved into a more deeply nested construct.

CombineAccessChains = 6

Create a pass to combine chained access chains. This pass looks for access chains fed by other access chains and combines them into a single instruction where possible.

CompactIds = 7

Creates a compact ids pass. The pass remaps result ids to a compact and gapless range starting from %1.

ConvertRelaxedToHalf = 8

Create pass to convert relaxed precision instructions to half precision. This pass converts as many relaxed float32 arithmetic operations to half as possible. It converts any float32 operands to half if needed. It converts any resulting half precision values back to float32 as needed. No variables are changed. No image operations are changed.

Best if run after function scope store/load and composite operation eliminations are run. Also best if followed by instruction simplification, redundancy elimination and DCE.

CopyPropagateArrays = 9

Create copy propagate arrays pass. This pass looks to copy propagate memory references for arrays. It looks for specific code patterns to recognize array copies.

DeadBranchElim = 10

Create dead branch elimination pass. For each entry point function, this pass will look for SelectionMerge BranchConditionals with constant condition and convert to a Branch to the indicated label. It will delete resulting dead blocks.

For all phi functions in merge block, replace all uses with the id corresponding to the living predecessor.

Note that some branches and blocks may be left to avoid creating invalid control flow. Improving this is left to future work.

This pass is most effective when preceeded by passes which eliminate local loads and stores, effectively propagating constant values where possible.

DeadInsertElim = 11

Creates a dead insert elimination pass. This pass processes each entry point function in the module, searching for unreferenced inserts into composite types. These are most often unused stores to vector components. They are unused because they are never referenced, or because there is another insert to the same component between the insert and the reference. After removing the inserts, dead code elimination is attempted on the inserted values.

This pass performs best after access chains are converted to inserts and extracts and local loads and stores are eliminated. While executing this pass can be advantageous on its own, it is also advantageous to execute this pass after CreateInsertExtractPass() as it will remove any unused inserts created by that pass.

DeadVariableElimination = 12

Create dead variable elimination pass. This pass will delete module scope variables, along with their decorations, that are not referenced.

DescriptorScalarReplacement = 13

Create descriptor scalar replacement pass. This pass replaces every array variable |desc| that has a DescriptorSet and Binding decorations with a new variable for each element of the array. Suppose |desc| was bound at binding |b|. Then the variable corresponding to |desc[i]| will have binding |b+i|. The descriptor set will be the same. It is assumed that no other variable already has a binding that will used by one of the new variables. If not, the pass will generate invalid Spir-V. All accesses to |desc| must be OpAccessChain instructions with a literal index for the first index.

EliminateDeadConstant = 14

Creates a eliminate-dead-constant pass. A eliminate-dead-constant pass removes dead constants, including normal contants defined by OpConstant, OpConstantComposite, OpConstantTrue, or OpConstantFalse and spec constants defined by OpSpecConstant, OpSpecConstantComposite, OpSpecConstantTrue, OpSpecConstantFalse or OpSpecConstantOp.

EliminateDeadFunctions = 15

Creates an eliminate-dead-functions pass. An eliminate-dead-functions pass will remove all functions that are not in the call trees rooted at entry points and exported functions. These functions are not needed because they will never be called.

EliminateDeadMembers = 16

Creates an eliminate-dead-members pass. An eliminate-dead-members pass will remove all unused members of structures. This will not affect the data layout of the remaining members.

FixStorageClass = 17

Create a pass to fix incorrect storage classes. In order to make code generation simpler, DXC may generate code where the storage classes do not match up correctly. This pass will fix the errors that it can.

FlattenDecoration = 18

Creates a flatten-decoration pass. A flatten-decoration pass replaces grouped decorations with equivalent ungrouped decorations. That is, it replaces each OpDecorationGroup instruction and associated OpGroupDecorate and OpGroupMemberDecorate instructions with equivalent OpDecorate and OpMemberDecorate instructions. The pass does not attempt to preserve debug information for instructions it removes.

FoldSpecConstantOpAndComposite = 19

Creates a fold-spec-constant-op-and-composite pass. A fold-spec-constant-op-and-composite pass folds spec constants defined by OpSpecConstantOp or OpSpecConstantComposite instruction, to normal Constants defined by OpConstantTrue, OpConstantFalse, OpConstant, OpConstantNull, or OpConstantComposite instructions. Note that spec constants defined with OpSpecConstant, OpSpecConstantTrue, or OpSpecConstantFalse instructions are not handled, as these instructions indicate their value are not determined and can be changed in future. A spec constant is foldable if all of its value(s) can be determined from the module. E.g., an integer spec constant defined with OpSpecConstantOp instruction can be folded if its value won’t change later. This pass will replace the original OpSpecContantOp instruction with an OpConstant instruction. When folding composite spec constants, new instructions may be inserted to define the components of the composite constant first, then the original spec constants will be replaced by OpConstantComposite instructions.

There are some operations not supported yet: OpSConvert, OpFConvert, OpQuantizeToF16 and all the operations under Kernel capability. TODO(qining): Add support for the operations listed above.

FreezeSpecConstantValue = 20

Creates a freeze-spec-constant-value pass. A freeze-spec-constant pass specializes the value of spec constants to their default values. This pass only processes the spec constants that have SpecId decorations (defined by OpSpecConstant, OpSpecConstantTrue, or OpSpecConstantFalse instructions) and replaces them with their normal counterparts (OpConstant, OpConstantTrue, or OpConstantFalse). The corresponding SpecId annotation instructions will also be removed. This pass does not fold the newly added normal constants and does not process other spec constants defined by OpSpecConstantComposite or OpSpecConstantOp.

GraphicsRobustAccess = 21

Creates a graphics robust access pass.

This pass injects code to clamp indexed accesses to buffers and internal arrays, providing guarantees satisfying Vulkan’s robustBufferAccess rules.

TODO(dneto): Clamps coordinates and sample index for pointer calculations into storage images (OpImageTexelPointer). For an cube array image, it assumes the maximum layer count times 6 is at most 0xffffffff.

NOTE: This pass will fail with a message if:

• The module is not a Shader module.
• The module declares VariablePointers, VariablePointersStorageBuffer, or RuntimeDescriptorArrayEXT capabilities.
• The module uses an addressing model other than Logical
• Access chain indices are wider than 64 bits.
• Access chain index for a struct is not an OpConstant integer or is out of range. (The module is already invalid if that is the case.)
• TODO(dneto): The OpImageTexelPointer coordinate component is not 32-bits wide.

NOTE: Access chain indices are always treated as signed integers. So if an array has a fixed size of more than 2^31 elements, then elements from 2^31 and above are never accessible with a 32-bit index, signed or unsigned. For this case, this pass will clamp the index between 0 and at 2^31-1, inclusive. Similarly, if an array has more then 2^15 element and is accessed with a 16-bit index, then elements from 2^15 and above are not accessible. In this case, the pass will clamp the index between 0 and 2^15-1 inclusive.

IfConversion = 22

Creates a pass that converts if-then-else like assignments into OpSelect.

InlineExhaustive = 23

Creates an exhaustive inline pass. An exhaustive inline pass attempts to exhaustively inline all function calls in all functions in an entry point call tree. The intent is to enable, albeit through brute force, analysis and optimization across function calls by subsequent optimization passes. As the inlining is exhaustive, there is no attempt to optimize for size or runtime performance. Functions that are not in the call tree of an entry point are not changed.

InlineOpaque = 24

Creates an opaque inline pass. An opaque inline pass inlines all function calls in all functions in all entry point call trees where the called function contains an opaque type in either its parameter types or return type. An opaque type is currently defined as Image, Sampler or SampledImage. The intent is to enable, albeit through brute force, analysis and optimization across these function calls by subsequent passes in order to remove the storing of opaque types which is not legal in Vulkan. Functions that are not in the call tree of an entry point are not changed.

InsertExtractElim = 25

Creates an insert/extract elimination pass. This pass processes each entry point function in the module, searching for extracts on a sequence of inserts. It further searches the sequence for an insert with indices identical to the extract. If such an insert can be found before hitting a conflicting insert, the extract’s result id is replaced with the id of the values from the insert.

Besides removing extracts this pass enables subsequent dead code elimination passes to delete the inserts. This pass performs best after access chains are converted to inserts and extracts and local loads and stores are eliminated.

InterpolateFixup = 26

Replaces the internal version of GLSLstd450 InterpolateAt* extended instructions with the externally valid version. The internal version allows an OpLoad of the interpolant for the first argument. This pass removes the OpLoad and replaces it with its pointer. glslang and possibly other frontends will create the internal version for HLSL. This pass will be part of HLSL legalization and should be called after interpolants have been propagated into their final positions.

LocalAccessChainConvert = 27

Creates a local access chain conversion pass. A local access chain conversion pass identifies all function scope variables which are accessed only with loads, stores and access chains with constant indices. It then converts all loads and stores of such variables into equivalent sequences of loads, stores, extracts and inserts.

This pass only processes entry point functions. It currently only converts non-nested, non-ptr access chains. It does not process modules with non-32-bit integer types present. Optional memory access options on loads and stores are ignored as we are only processing function scope variables.

This pass unifies access to these variables to a single mode and simplifies subsequent analysis and elimination of these variables along with their loads and stores allowing values to propagate to their points of use where possible.

LocalMultiStoreElim = 28

Creates an SSA local variable load/store elimination pass. For every entry point function, eliminate all loads and stores of function scope variables only referenced with non-access-chain loads and stores. Eliminate the variables as well.

The presence of access chain references and function calls can inhibit the above optimization.

Only shader modules with relaxed logical addressing (see opt/instruction.h) are currently processed. Currently modules with any extensions enabled are not processed. This is left for future work.

This pass is most effective if preceeded by Inlining and LocalAccessChainConvert. LocalSingleStoreElim and LocalSingleBlockElim will reduce the work that this pass has to do.

LocalRedundancyElimination = 29

Create value numbering pass. This pass will look for instructions in the same basic block that compute the same value, and remove the redundant ones.

LocalSingleBlockLoadStoreElim = 30

Creates a single-block local variable load/store elimination pass. For every entry point function, do single block memory optimization of function variables referenced only with non-access-chain loads and stores. For each targeted variable load, if previous store to that variable in the block, replace the load’s result id with the value id of the store. If previous load within the block, replace the current load’s result id with the previous load’s result id. In either case, delete the current load. Finally, check if any remaining stores are useless, and delete store and variable if possible.

The presence of access chain references and function calls can inhibit the above optimization.

Only modules with relaxed logical addressing (see opt/instruction.h) are currently processed.

This pass is most effective if preceeded by Inlining and LocalAccessChainConvert. This pass will reduce the work needed to be done by LocalSingleStoreElim and LocalMultiStoreElim.

Only functions in the call tree of an entry point are processed.

LocalSingleStoreElim = 31

Creates a local single store elimination pass. For each entry point function, this pass eliminates loads and stores for function scope variable that are stored to only once, where possible. Only whole variable loads and stores are eliminated; access-chain references are not optimized. Replace all loads of such variables with the value that is stored and eliminate any resulting dead code.

Currently, the presence of access chains and function calls can inhibit this pass, however the Inlining and LocalAccessChainConvert passes can make it more effective. In additional, many non-load/store memory operations are not supported and will prohibit optimization of a function. Support of these operations are future work.

Only shader modules with relaxed logical addressing (see opt/instruction.h) are currently processed.

This pass will reduce the work needed to be done by LocalSingleBlockElim and LocalMultiStoreElim and can improve the effectiveness of other passes such as DeadBranchElimination which depend on values for their analysis.

LoopInvariantCodeMotion = 32

Create LICM pass. This pass will look for invariant instructions inside loops and hoist them to the loops preheader.

LoopPeeling = 33

Creates a loop peeling pass. This pass will look for conditions inside a loop that are true or false only for the N first or last iteration. For loop with such condition, those N iterations of the loop will be executed outside of the main loop. To limit code size explosion, the loop peeling can only happen if the code size growth for each loop is under |code_growth_threshold|.

LoopUnswitch = 34

Creates a loop unswitch pass. This pass will look for loop independent branch conditions and move the condition out of the loop and version the loop based on the taken branch. Works best after LICM and local multi store elimination pass.

MergeReturn = 35

create merge return pass. changes functions that have multiple return statements so they have a single return statement.

for structured control flow it is assumed that the only unreachable blocks in the function are trivial merge and continue blocks.

a trivial merge block contains the label and an opunreachable instructions, nothing else. a trivial continue block contain a label and an opbranch to the header, nothing else.

these conditions are guaranteed to be met after running dead-branch elimination.

Null = 36

Creates a null pass. A null pass does nothing to the SPIR-V module to be optimized.

PrivateToLocal = 37

Create a private to local pass. This pass looks for variables delcared in the private storage class that are used in only one function. Those variables are moved to the function storage class in the function that they are used.

PropagateLineInfo = 38

Create line propagation pass This pass propagates line information based on the rules for OpLine and OpNoline and clones an appropriate line instruction into every instruction which does not already have debug line instructions.

This pass is intended to maximize preservation of source line information through passes which delete, move and clone instructions. Ideally it should be run before any such pass. It is a bookend pass with EliminateDeadLines which can be used to remove redundant line instructions at the end of a run of such passes and reduce final output file size.

ReduceLoadSize = 39

Create a pass to reduce the size of loads. This pass looks for loads of structures where only a few of its members are used. It replaces the loads feeding an OpExtract with an OpAccessChain and a load of the specific elements.

RedundancyElimination = 40

Create global value numbering pass. This pass will look for instructions where the same value is computed on all paths leading to the instruction. Those instructions are deleted.

RedundantLineInfoElim = 41

Create dead line elimination pass This pass eliminates redundant line instructions based on the rules for OpLine and OpNoline. Its main purpose is to reduce the size of the file need to store the SPIR-V without losing line information.

This is a bookend pass with PropagateLines which attaches line instructions to every instruction to preserve line information during passes which delete, move and clone instructions. DeadLineElim should be run after PropagateLines and all such subsequent passes. Normally it would be one of the last passes to be run.

RelaxFloatOps = 42

Create relax float ops pass. This pass decorates all float32 result instructions with RelaxedPrecision if not already so decorated.

RemoveDuplicates = 43

Creates a remove duplicate pass. This pass removes various duplicates:

• duplicate capabilities;
• duplicate extended instruction imports;
• duplicate types;
• duplicate decorations.

RemoveUnusedInterfaceVariables = 44

Creates a remove-unused-interface-variables pass. Removes variables referenced on the |OpEntryPoint| instruction that are not referenced in the entry point function or any function in its call tree. Note that this could cause the shader interface to no longer match other shader stages.

ReplaceInvalidOpcode = 45

Creates a pass that will replace instructions that are not valid for the current shader stage by constants. Has no effect on non-shader modules.

Simplification = 46

Creates a pass that simplifies instructions using the instruction folder.

SSARewrite = 47

Create the SSA rewrite pass. This pass converts load/store operations on function local variables into operations on SSA IDs. This allows SSA optimizers to act on these variables. Only variables that are local to the function and of supported types are processed (see IsSSATargetVar for details).

StrengthReduction = 48

Creates a strength-reduction pass. A strength-reduction pass will look for opportunities to replace an instruction with an equivalent and less expensive one. For example, multiplying by a power of 2 can be replaced by a bit shift.

StripDebugInfo = 49

Creates a strip-debug-info pass. A strip-debug-info pass removes all debug instructions (as documented in Section 3.32.2 of the SPIR-V spec) of the SPIR-V module to be optimized.

StripNonSemanticInfo = 50

Creates a strip-nonsemantic-info pass. A strip-nonsemantic-info pass removes all reflections and explicitly non-semantic instructions.

UnifyConstant = 51

Creates a unify-constant pass. A unify-constant pass de-duplicates the constants. Constants with the exact same value and identical form will be unified and only one constant will be kept for each unique pair of type and value. There are several cases not handled by this pass:

1. Constants defined by OpConstantNull instructions (null constants) and constants defined by OpConstantFalse, OpConstant or OpConstantComposite with value 0 (zero-valued normal constants) are not considered equivalent. So null constants won’t be used to replace zero-valued normal constants, vice versa.
2. Whenever there are decorations to the constant’s result id id, the constant won’t be handled, which means, it won’t be used to replace any other constants, neither can other constants replace it.
3. NaN in float point format with different bit patterns are not unified.

UpgradeMemoryModel = 52

Create a pass to upgrade to the VulkanKHR memory model. This pass upgrades the Logical GLSL450 memory model to Logical VulkanKHR. Additionally, it modifies memory, image, atomic and barrier operations to conform to that model’s requirements.

VectorDCE = 53

Create a vector dce pass. This pass looks for components of vectors that are unused, and removes them from the vector. Note this would still leave around lots of dead code that a pass of ADCE will be able to remove.

Workaround1209 = 54

Creates a workaround driver bugs pass. This pass attempts to work around a known driver bug (issue #1209) by identifying the bad code sequences and rewriting them.

Current workaround: Avoid OpUnreachable instructions in loops.

WrapOpKill = 55

Create a pass to replace each OpKill instruction with a function call to a function that has a single OpKill. Also replace each OpTerminateInvocation instruction with a function call to a function that has a single OpTerminateInvocation. This allows more code to be inlined.

Trait Implementations

impl Clone for Passes

fn clone(&self) -> Passes

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Passes

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Copy for Passes