Standard Dialect

This dialect provides documentation for operations within the Standard dialect.

Note: This dialect is a collection of operations for several different concepts, and should be split into multiple more-focused dialects accordingly.

[TOC]

TODO: shape, which returns a 1D tensor, and can take an unknown rank tensor as input.

TODO: rank, which returns an index.

Terminator operations

Terminator operations are required at the end of each block. They may contain a list of successors, i.e. other blocks to which the control flow will proceed.

'br' terminator operation

Syntax:

operation ::= `br` successor
successor ::= bb-id branch-use-list?
branch-use-list ::= `(` ssa-use-list `:` type-list-no-parens `)`

The br terminator operation represents an unconditional jump to a target block. The count and types of operands to the branch must align with the arguments in the target block.

The MLIR branch operation is not allowed to target the entry block for a region.

'cond_br' terminator operation

Syntax:

operation ::= `cond_br` ssa-use `,` successor `,` successor

The cond_br terminator operation represents a conditional branch on a boolean (1-bit integer) value. If the bit is set, then the first destination is jumped to; if it is false, the second destination is chosen. The count and types of operands must align with the arguments in the corresponding target blocks.

The MLIR conditional branch operation is not allowed to target the entry block for a region. The two destinations of the conditional branch operation are allowed to be the same.

The following example illustrates a function with a conditional branch operation that targets the same block:

func @select(i32, i32, i1) -> i32 {
^bb0(%a : i32, %b :i32, %flag : i1) :
    // Both targets are the same, operands differ
    cond_br %flag, ^bb1(%a : i32), ^bb1(%b : i32)

^bb1(%x : i32) :
    return %x : i32
}

'return' terminator operation

Syntax:

operation ::= `return` (ssa-use-list `:` type-list-no-parens)?

The return terminator operation represents the completion of a function, and produces the result values. The count and types of the operands must match the result types of the enclosing function. It is legal for multiple blocks in a single function to return.

Core Operations

'call' operation

Syntax:

operation ::=
    (ssa-id `=`)? `call` symbol-ref-id `(` ssa-use-list? `)` `:` function-type

The call operation represents a direct call to a function. The operands and result types of the call must match the specified function type. The callee is encoded as a function attribute named "callee".

Example:

// Calling the function my_add.
%31 = call @my_add(%0, %1) : (tensor<16xf32>, tensor<16xf32>) -> tensor<16xf32>

'call_indirect' operation

Syntax:

operation ::= `call_indirect` ssa-use `(` ssa-use-list? `)` `:` function-type

The call_indirect operation represents an indirect call to a value of function type. Functions are first class types in MLIR, and may be passed as arguments and merged together with block arguments. The operands and result types of the call must match the specified function type.

Function values can be created with the constant operation.

Example:

%31 = call_indirect %15(%0, %1)
        : (tensor<16xf32>, tensor<16xf32>) -> tensor<16xf32>

'dim' operation

Syntax:

operation ::= ssa-id `=` `dim` ssa-id `,` integer-literal `:` type

The dim operation takes a memref or tensor operand and a dimension index, and returns an index that is the size of that dimension.

The dim operation is represented with a single integer attribute named index, and the type specifies the type of the memref or tensor operand.

Examples:

// Always returns 4, can be constant folded:
%x = dim %A, 0 : tensor<4 x ? x f32>

// Returns the dynamic dimension of %A.
%y = dim %A, 1 : tensor<4 x ? x f32>

// Equivalent generic form:
%x = "std.dim"(%A) {index = 0 : i64} : (tensor<4 x ? x f32>) -> index
%y = "std.dim"(%A) {index = 1 : i64} : (tensor<4 x ? x f32>) -> index

Memory Operations

'alloc' operation

Syntax:

operation ::= ssa-id `=` `alloc` dim-and-symbol-use-list `:` memref-type

Allocates a new memref of specified type. Values required for dynamic dimension sizes are passed as arguments in parentheses (in the same order in which they appear in the shape signature of the memref) while the symbols required by the layout map are passed in the square brackets in lexicographical order. If no layout maps are specified in the memref, then an identity mapping is used.

The buffer referenced by a memref type is created by the alloc operation, and destroyed by the dealloc operation.

Example:

// Allocating memref for a fully static shape.
%A = alloc() : memref<1024x64xf32, #layout_map0, memspace0>

// %M, %N, %x, %y are SSA values of integer type.  M and N are bound to the
// two unknown dimensions of the type and x/y are bound to symbols in
// #layout_map1.
%B = alloc(%M, %N)[%x, %y] : memref<?x?xf32, #layout_map1, memspace1>

'alloc_static' operation

Syntax:

operation ::=
    ssa-id `=` `alloc_static` `(` integer-literal `)` :  memref-type

Allocates a new memref of specified type with a fixed base pointer location in memory. 'alloc_static' does not support types that have dynamic shapes or that require dynamic symbols in their layout function (use the alloc operation in those cases).

Example:

%A = alloc_static(0x1232a00) : memref<1024 x 64 x f32, #layout_map0, memspace0>

The alloc_static operation is used to represent code after buffer allocation has been performed.

'dealloc' operation

Syntax:

operation ::= `dealloc` ssa-use `:` memref-type

Delineates the end of the lifetime of the memory corresponding to a memref allocation. It is paired with an alloc or alloc_static operation.

Example:

dealloc %A : memref<128 x f32, #layout, memspace0>

'dma_start' operation

Syntax:

operation ::= `dma_start` ssa-use`[`ssa-use-list`]` `,`
               ssa-use`[`ssa-use-list`]` `,` ssa-use `,`
               ssa-use`[`ssa-use-list`]` (`,` ssa-use `,` ssa-use)?
              `:` memref-type `,` memref-type `,` memref-type

Starts a non-blocking DMA operation that transfers data from a source memref to a destination memref. The operands include the source and destination memref's each followed by its indices, size of the data transfer in terms of the number of elements (of the elemental type of the memref), a tag memref with its indices, and optionally two additional arguments corresponding to the stride (in terms of number of elements) and the number of elements to transfer per stride. The tag location is used by a dma_wait operation to check for completion. The indices of the source memref, destination memref, and the tag memref have the same restrictions as any load/store operation in a affine context (whenever DMA operations appear in an affine context). See restrictions on dimensions and symbols in affine contexts. This allows powerful static analysis and transformations in the presence of such DMAs including rescheduling, pipelining / overlap with computation, and checking for matching start/end operations. The source and destination memref need not be of the same dimensionality, but need to have the same elemental type.

For example, a dma_start operation that transfers 32 vector elements from a memref %src at location [%i, %j] to memref %dst at [%k, %l] would be specified as shown below.

Example:

%size = constant 32 : index
%tag = alloc() : memref<1 x i32, affine_map<(d0) -> (d0)>, 4>
%idx = constant 0 : index
dma_start %src[%i, %j], %dst[%k, %l], %size, %tag[%idx] :
     memref<40 x 8 x vector<16xf32>, affine_map<(d0, d1) -> (d0, d1)>, 0>,
     memref<2 x 4 x vector<16xf32>, affine_map<(d0, d1) -> (d0, d1)>, 2>,
     memref<1 x i32>, affine_map<(d0) -> (d0)>, 4>

'dma_wait' operation

Syntax:

operation ::= `dma_wait` ssa-use`[`ssa-use-list`]` `,` ssa-use `:` memref-type

Blocks until the completion of a DMA operation associated with the tag element specified with a tag memref and its indices. The operands include the tag memref followed by its indices and the number of elements associated with the DMA being waited on. The indices of the tag memref have the same restrictions as load/store indices.

Example:

dma_wait %tag[%idx], %size : memref<1 x i32, affine_map<(d0) -> (d0)>, 4>

'extract_element' operation

Syntax:

operation ::= ssa-id `=` `extract_element` ssa-use `[` ssa-use-list `]` `:` type

The extract_element op reads a tensor or vector and returns one element from it specified by an index list. The output of the 'extract_element' is a new value with the same type as the elements of the tensor or vector. The arity of indices matches the rank of the accessed value (i.e., if a tensor is of rank 3, then 3 indices are required for the extract. The indices should all be of index type.

Examples:

%3 = extract_element %v[%1, %2] : vector<4x4xi32>
%4 = extract_element %t[%1, %2] : tensor<4x4xi32>
%5 = extract_element %ut[%1, %2] : tensor<*xi32>

'load' operation

Syntax:

operation ::= ssa-id `=` `load` ssa-use `[` ssa-use-list `]` `:` memref-type

The load op reads an element from a memref specified by an index list. The output of load is a new value with the same type as the elements of the memref. The arity of indices is the rank of the memref (i.e., if the memref loaded from is of rank 3, then 3 indices are required for the load following the memref identifier).

In an affine.if or affine.for body, the indices of a load are restricted to SSA values bound to surrounding loop induction variables, symbols, results of a constant operation, or the result of an affine.apply operation that can in turn take as arguments all of the aforementioned SSA values or the recursively result of such an affine.apply operation.

Example:

%1 = affine.apply affine_map<(d0, d1) -> (3*d0)> (%i, %j)
%2 = affine.apply affine_map<(d0, d1) -> (d1+1)> (%i, %j)
%12 = load %A[%1, %2] : memref<8x?xi32, #layout, memspace0>

// Example of an indirect load (treated as non-affine)
%3 = affine.apply affine_map<(d0) -> (2*d0 + 1)>(%12)
%13 = load %A[%3, %2] : memref<4x?xi32, #layout, memspace0>

Context: The load and store operations are specifically crafted to fully resolve a reference to an element of a memref, and (in affine affine.if and affine.for operations) the compiler can follow use-def chains (e.g. through affine.apply operations) to precisely analyze references at compile-time using polyhedral techniques. This is possible because of the restrictions on dimensions and symbols in these contexts.

'splat' operation

Syntax:

operation ::= ssa-id `=` `splat` ssa-use `:` ( vector-type | tensor-type )

Broadcast the operand to all elements of the result vector or tensor. The operand has to be of either integer or float type. When the result is a tensor, it has to be statically shaped.

Example:

  %s = load %A[%i] : memref<128xf32>
  %v = splat %s : vector<4xf32>
  %t = splat %s : tensor<8x16xi32>

TODO: This operation is easy to extend to broadcast to dynamically shaped tensors in the same way dynamically shaped memrefs are handled.

// Broadcasts %s to a 2-d dynamically shaped tensor, with %m, %n binding
// to the sizes of the two dynamic dimensions.
%m = "foo"() : () -> (index)
%n = "bar"() : () -> (index)
%t = splat %s [%m, %n] : tensor<?x?xi32>

'store' operation

Syntax:

operation ::= `store` ssa-use `,` ssa-use `[` ssa-use-list `]` `:` memref-type

Store value to memref location given by indices. The value stored should have the same type as the elemental type of the memref. The number of arguments provided within brackets need to match the rank of the memref.

In an affine context, the indices of a store are restricted to SSA values bound to surrounding loop induction variables, symbols, results of a constant operation, or the result of an affine.apply operation that can in turn take as arguments all of the aforementioned SSA values or the recursively result of such an affine.apply operation.

Example:

store %100, %A[%1, 1023] : memref<4x?xf32, #layout, memspace0>

Context: The load and store operations are specifically crafted to fully resolve a reference to an element of a memref, and (in polyhedral affine.if and affine.for operations) the compiler can follow use-def chains (e.g. through affine.apply operations) to precisely analyze references at compile-time using polyhedral techniques. This is possible because of the restrictions on dimensions and symbols in these contexts.

'tensor_load' operation

Syntax:

operation ::= ssa-id `=` `tensor_load` ssa-use-and-type

Create a tensor from a memref, making an independent copy of the element data. The result value is a tensor whose shape and element type match the memref operand.

Example:

// Produces a value of tensor<4x?xf32> type.
%12 = tensor_load %10 : memref<4x?xf32, #layout, memspace0>

'tensor_store' operation

Syntax:

operation ::= `tensor_store` ssa-use `,` ssa-use `:` memref-type

Stores the contents of a tensor into a memref. The first operand is a value of tensor type, the second operand is a value of memref type. The shapes and element types of these must match, and are specified by the memref type.

Example:

%9 = dim %8, 1 : tensor<4x?xf32>
%10 = alloc(%9) : memref<4x?xf32, #layout, memspace0>
tensor_store %8, %10 : memref<4x?xf32, #layout, memspace0>

Unary Operations

'absf' operation

Syntax:

operation ::= ssa-id `=` `absf` ssa-use `:` type

Examples:

// Scalar absolute value.
%a = absf %b : f64

// SIMD vector element-wise absolute value.
%f = absf %g : vector<4xf32>

// Tensor element-wise absolute value.
%x = absf %y : tensor<4x?xf8>

The absf operation computes the absolute value. It takes one operand and returns one result of the same type. This type may be a float scalar type, a vector whose element type is float, or a tensor of floats. It has no standard attributes.

'ceilf' operation

Syntax:

operation ::= ssa-id `=` `ceilf` ssa-use `:` type

Examples:

// Scalar ceiling value.
%a = ceilf %b : f64

// SIMD vector element-wise ceiling value.
%f = ceilf %g : vector<4xf32>

// Tensor element-wise ceiling value.
%x = ceilf %y : tensor<4x?xf8>

The ceilf operation computes the ceiling of a given value. It takes one operand and returns one result of the same type. This type may be a float scalar type, a vector whose element type is float, or a tensor of floats. It has no standard attributes.

'cos' operation

Syntax:

operation ::= ssa-id `=` `cos` ssa-use `:` type

Examples:

// Scalar cosine value.
%a = cos %b : f64

// SIMD vector element-wise cosine value.
%f = cos %g : vector<4xf32>

// Tensor element-wise cosine value.
%x = cos %y : tensor<4x?xf8>

The cos operation computes the cosine of a given value. It takes one operand and returns one result of the same type. This type may be a float scalar type, a vector whose element type is float, or a tensor of floats. It has no standard attributes.

'exp' operation

Syntax:

operation ::= ssa-id `=` `exp` ssa-use `:` type

Examples:

// Scalar natural exponential.
%a = exp %b : f64

// SIMD vector element-wise natural exponential.
%f = exp %g : vector<4xf32>

// Tensor element-wise natural exponential.
%x = exp %y : tensor<4x?xf8>

The exp operation takes one operand and returns one result of the same type. This type may be a float scalar type, a vector whose element type is float, or a tensor of floats. It has no standard attributes.

'negf' operation

Syntax:

operation ::= ssa-id `=` `negf` ssa-use `:` type

Examples:

// Scalar negation value.
%a = negf %b : f64

// SIMD vector element-wise negation value.
%f = negf %g : vector<4xf32>

// Tensor element-wise negation value.
%x = negf %y : tensor<4x?xf8>

The negf operation computes the negation of a given value. It takes one operand and returns one result of the same type. This type may be a float scalar type, a vector whose element type is float, or a tensor of floats. It has no standard attributes.

'tanh' operation

Syntax:

operation ::= ssa-id `=` `tanh` ssa-use `:` type

Examples:

// Scalar hyperbolic tangent value.
%a = tanh %b : f64

// SIMD vector element-wise hyperbolic tangent value.
%f = tanh %g : vector<4xf32>

// Tensor element-wise hyperbolic tangent value.
%x = tanh %y : tensor<4x?xf8>

The tanh operation computes the hyperbolic tangent. It takes one operand and returns one result of the same type. This type may be a float scalar type, a vector whose element type is float, or a tensor of floats. It has no standard attributes.

Arithmetic Operations

Basic arithmetic in MLIR is specified by standard operations described in this section.

'addi' operation

Syntax:

operation ::= ssa-id `=` `addi` ssa-use `,` ssa-use `:` type

Examples:

// Scalar addition.
%a = addi %b, %c : i64

// SIMD vector element-wise addition, e.g. for Intel SSE.
%f = addi %g, %h : vector<4xi32>

// Tensor element-wise addition.
%x = addi %y, %z : tensor<4x?xi8>

The addi operation takes two operands and returns one result, each of these is required to be the same type. This type may be an integer scalar type, a vector whose element type is integer, or a tensor of integers. It has no standard attributes.

'addf' operation

Syntax:

operation ::= ssa-id `=` `addf` ssa-use `,` ssa-use `:` type

Examples:

// Scalar addition.
%a = addf %b, %c : f64

// SIMD vector addition, e.g. for Intel SSE.
%f = addf %g, %h : vector<4xf32>

// Tensor addition.
%x = addf %y, %z : tensor<4x?xbf16>

The addf operation takes two operands and returns one result, each of these is required to be the same type. This type may be a floating point scalar type, a vector whose element type is a floating point type, or a floating point tensor.

It has no standard attributes.

TODO: In the distant future, this will accept optional attributes for fast math, contraction, rounding mode, and other controls.

'and' operation

Bitwise integer and.

Syntax:

operation ::= ssa-id `=` `and` ssa-use `,` ssa-use `:` type

Examples:

// Scalar integer bitwise and.
%a = and %b, %c : i64

// SIMD vector element-wise bitwise integer and.
%f = and %g, %h : vector<4xi32>

// Tensor element-wise bitwise integer and.
%x = and %y, %z : tensor<4x?xi8>

The and operation takes two operands and returns one result, each of these is required to be the same type. This type may be an integer scalar type, a vector whose element type is integer, or a tensor of integers. It has no standard attributes.

'cmpi' operation

Syntax:

operation ::= ssa-id `=` `cmpi` string-literal `,` ssa-id `,` ssa-id `:` type

Examples:

// Custom form of scalar "signed less than" comparison.
%x = cmpi "slt", %lhs, %rhs : i32

// Generic form of the same operation.
%x = "std.cmpi"(%lhs, %rhs) {predicate = 2 : i64} : (i32, i32) -> i1

// Custom form of vector equality comparison.
%x = cmpi "eq", %lhs, %rhs : vector<4xi64>

// Generic form of the same operation.
%x = "std.cmpi"(%lhs, %rhs) {predicate = 0 : i64}
    : (vector<4xi64>, vector<4xi64>) -> vector<4xi1>

The cmpi operation is a generic comparison for integer-like types. Its two arguments can be integers, vectors or tensors thereof as long as their types match. The operation produces an i1 for the former case, a vector or a tensor of i1 with the same shape as inputs in the other cases.

Its first argument is an attribute that defines which type of comparison is performed. The following comparisons are supported:

• equal (mnemonic: "eq"; integer value: 0)
• not equal (mnemonic: "ne"; integer value: 1)
• signed less than (mnemonic: "slt"; integer value: 2)
• signed less than or equal (mnemonic: "sle"; integer value: 3)
• signed greater than (mnemonic: "sgt"; integer value: 4)
• signed greater than or equal (mnemonic: "sge"; integer value: 5)
• unsigned less than (mnemonic: "ult"; integer value: 6)
• unsigned less than or equal (mnemonic: "ule"; integer value: 7)
• unsigned greater than (mnemonic: "ugt"; integer value: 8)
• unsigned greater than or equal (mnemonic: "uge"; integer value: 9)

The result is 1 if the comparison is true and 0 otherwise. For vector or tensor operands, the comparison is performed elementwise and the element of the result indicates whether the comparison is true for the operand elements with the same indices as those of the result.

Note: while the custom assembly form uses strings, the actual underlying attribute has integer type (or rather enum class in C++ code) as seen from the generic assembly form. String literals are used to improve readability of the IR by humans.

This operation only applies to integer-like operands, but not floats. The main reason being that comparison operations have diverging sets of attributes: integers require sign specification while floats require various floating point-related particularities, e.g., -ffast-math behavior, IEEE754 compliance, etc (rationale). The type of comparison is specified as attribute to avoid introducing ten similar operations, taking into account that they are often implemented using the same operation downstream (rationale). The separation between signed and unsigned order comparisons is necessary because of integers being signless. The comparison operation must know how to interpret values with the foremost bit being set: negatives in two's complement or large positives (rationale).

'constant' operation

Syntax:

operation ::= ssa-id `=` `constant` attribute-value `:` type

The constant operation produces an SSA value equal to some constant specified by an attribute. This is the way that MLIR uses to form simple integer and floating point constants, as well as more exotic things like references to functions and (TODO!) tensor/vector constants.

The constant operation is represented with a single attribute named "value". The type specifies the result type of the operation.

Examples:

// Integer constant
%1 = constant 42 : i32

// Reference to function @myfn.
%3 = constant @myfn : (tensor<16xf32>, f32) -> tensor<16xf32>

// Equivalent generic forms
%1 = "std.constant"() {value = 42 : i32} : () -> i32
%3 = "std.constant"() {value = @myfn}
   : () -> ((tensor<16xf32>, f32) -> tensor<16xf32>)

MLIR does not allow direct references to functions in SSA operands because the compiler is multithreaded, and disallowing SSA values to directly reference a function simplifies this (rationale).

'copysign' operation

Syntax:

operation ::= ssa-id `=` `copysign` ssa-use `:` type

Examples:

// Scalar copysign value.
%a = copysign %b %c : f64

// SIMD vector element-wise copysign value.
%f = copysign %g %h : vector<4xf32>

// Tensor element-wise copysign value.
%x = copysign %y %z : tensor<4x?xf8>

The copysign returns a value with the magnitude of the first operand and the sign of the second operand. It takes two operands and returns one result of the same type. This type may be a float scalar type, a vector whose element type is float, or a tensor of floats. It has no standard attributes.

'divis' operation

Signed integer division. Rounds towards zero. Treats the leading bit as sign, i.e. 6 / -2 = -3.

Note: the semantics of division by zero or signed division overflow (minimum value divided by -1) is TBD; do NOT assume any specific behavior.

Syntax:

operation ::= ssa-id `=` `divis` ssa-use `,` ssa-use `:` type

Examples:

// Scalar signed integer division.
%a = divis %b, %c : i64

// SIMD vector element-wise division.
%f = divis %g, %h : vector<4xi32>

// Tensor element-wise integer division.
%x = divis %y, %z : tensor<4x?xi8>

The divis operation takes two operands and returns one result, each of these is required to be the same type. This type may be an integer scalar type, a vector whose element type is integer, or a tensor of integers. It has no standard attributes.

'diviu' operation

Unsigned integer division. Rounds towards zero. Treats the leading bit as the most significant, i.e. for i16 given two's complement representation, 6 / -2 = 6 / (2^16 - 2) = 0.

Note: the semantics of division by zero is TBD; do NOT assume any specific behavior.

Syntax:

operation ::= ssa-id `=` `diviu` ssa-use `,` ssa-use `:` type

Examples:

// Scalar unsigned integer division.
%a = diviu %b, %c : i64

// SIMD vector element-wise division.
%f = diviu %g, %h : vector<4xi32>

// Tensor element-wise integer division.
%x = diviu %y, %z : tensor<4x?xi8>

The diviu operation takes two operands and returns one result, each of these is required to be the same type. This type may be an integer scalar type, a vector whose element type is integer, or a tensor of integers. It has no standard attributes.

'memref_cast' operation

Syntax:

operation ::= ssa-id `=` `memref_cast` ssa-use `:` type `to` type

Examples:

// Discard static dimension information.
%3 = memref_cast %2 : memref<4x?xf32> to memref<?x?xf32>

// Convert to a type with more known dimensions.
%4 = memref_cast %3 : memref<?x?xf32> to memref<4x?xf32>

// Convert to a type with unknown rank.
%5 = memref_cast %3 : memref<?x?xf32> to memref<*xf32>

// Convert to a type with static rank.
%6 = memref_cast %5 : memref<*xf32> to memref<?x?xf32>

Convert a memref from one type to an equivalent type without changing any data elements. The types are equivalent if 1. they both have the same static rank, same element type, same mappings, same address space. The operation is invalid if converting to a mismatching constant dimension, or 2. exactly one of the operands have an unknown rank, and they both have the same element type and same address space. The operation is invalid if both operands are of dynamic rank or if converting to a mismatching static rank.

'mulf' operation

Syntax:

operation ::= ssa-id `=` `mulf` ssa-use `,` ssa-use `:` type

Examples:

// Scalar multiplication.
%a = mulf %b, %c : f64

// SIMD pointwise vector multiplication, e.g. for Intel SSE.
%f = mulf %g, %h : vector<4xf32>

// Tensor pointwise multiplication.
%x = mulf %y, %z : tensor<4x?xbf16>

The mulf operation takes two operands and returns one result, each of these is required to be the same type. This type may be a floating point scalar type, a vector whose element type is a floating point type, or a floating point tensor.

It has no standard attributes.

TODO: In the distant future, this will accept optional attributes for fast math, contraction, rounding mode, and other controls.

'or' operation

Bitwise integer or.

Syntax:

operation ::= ssa-id `=` `or` ssa-use `,` ssa-use `:` type

Examples:

// Scalar integer bitwise or.
%a = or %b, %c : i64

// SIMD vector element-wise bitwise integer or.
%f = or %g, %h : vector<4xi32>

// Tensor element-wise bitwise integer or.
%x = or %y, %z : tensor<4x?xi8>

The or operation takes two operands and returns one result, each of these is required to be the same type. This type may be an integer scalar type, a vector whose element type is integer, or a tensor of integers. It has no standard attributes.

'remis' operation

Signed integer division remainder. Treats the leading bit as sign, i.e. 6 % -2 = 0.

Note: the semantics of division by zero is TBD; do NOT assume any specific behavior.

Syntax:

operation ::= ssa-id `=` `remis` ssa-use `,` ssa-use `:` type

Examples:

// Scalar signed integer division remainder.
%a = remis %b, %c : i64

// SIMD vector element-wise division remainder.
%f = remis %g, %h : vector<4xi32>

// Tensor element-wise integer division remainder.
%x = remis %y, %z : tensor<4x?xi8>

The remis operation takes two operands and returns one result, each of these is required to be the same type. This type may be an integer scalar type, a vector whose element type is integer, or a tensor of integers. It has no standard attributes.

'remiu' operation

Unsigned integer division remainder. Treats the leading bit as the most significant, i.e. for i16, 6 % -2 = 6 % (2^16 - 2) = 6.

Note: the semantics of division by zero is TBD; do NOT assume any specific behavior.

Syntax:

operation ::= ssa-id `=` `remiu` ssa-use `,` ssa-use `:` type

Examples:

// Scalar unsigned integer division remainder.
%a = remiu %b, %c : i64

// SIMD vector element-wise division remainder.
%f = remiu %g, %h : vector<4xi32>

// Tensor element-wise integer division remainder.
%x = remiu %y, %z : tensor<4x?xi8>

The remiu operation takes two operands and returns one result, each of these is required to be the same type. This type may be an integer scalar type, a vector whose element type is integer, or a tensor of integers. It has no standard attributes.

'select' operation

Syntax:

operation ::= ssa-id `=` `select` ssa-use `,` ssa-use `,` ssa-use `:` type

Examples:

// Custom form of scalar selection.
%x = select %cond, %true, %false : i32

// Generic form of the same operation.
%x = "std.select"(%cond, %true, %false) : (i1, i32, i32) -> i32

// Vector selection is element-wise
%vx = "std.select"(%vcond, %vtrue, %vfalse)
    : (vector<42xi1>, vector<42xf32>, vector<42xf32>) -> vector<42xf32>

The select operation chooses one value based on a binary condition supplied as its first operand. If the value of the first operand is 1, the second operand is chosen, otherwise the third operand is chosen. The second and the third operand must have the same type.

The operation applies to vectors and tensors elementwise given the shape of all operands is identical. The choice is made for each element individually based on the value at the same position as the element in the condition operand.

The select operation combined with cmpi can be used to implement min and max with signed or unsigned comparison semantics.

'tensor_cast' operation

Syntax:

operation ::= ssa-id `=` `tensor_cast` ssa-use `:` type `to` type

Examples:

// Convert from unknown rank to rank 2 with unknown dimension sizes.
%2 = "std.tensor_cast"(%1) : (tensor<*xf32>) -> tensor<?x?xf32>
%2 = tensor_cast %1 : tensor<*xf32> to tensor<?x?xf32>

// Convert to a type with more known dimensions.
%3 = "std.tensor_cast"(%2) : (tensor<?x?xf32>) -> tensor<4x?xf32>

// Discard static dimension and rank information.
%4 = "std.tensor_cast"(%3) : (tensor<4x?xf32>) -> tensor<?x?xf32>
%5 = "std.tensor_cast"(%4) : (tensor<?x?xf32>) -> tensor<*xf32>

Convert a tensor from one type to an equivalent type without changing any data elements. The source and destination types must both be tensor types with the same element type. If both are ranked, then the rank should be the same and static dimensions should match. The operation is invalid if converting to a mismatching constant dimension.

'xor' operation

Bitwise integer xor.

Syntax:

operation ::= ssa-id `=` `xor` ssa-use, ssa-use `:` type

Examples:

// Scalar integer bitwise xor.
%a = xor %b, %c : i64

// SIMD vector element-wise bitwise integer xor.
%f = xor %g, %h : vector<4xi32>

// Tensor element-wise bitwise integer xor.
%x = xor %y, %z : tensor<4x?xi8>

The xor operation takes two operands and returns one result, each of these is required to be the same type. This type may be an integer scalar type, a vector whose element type is integer, or a tensor of integers. It has no standard attributes.