Clean up the list of operations somewhat.
This commit is contained in:
Jakob Stoklund Olesen
184
docs/langref.rst
184
docs/langref.rst
@@ -605,23 +605,32 @@ depends on the runtime environment.
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Operations
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==========
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The remaining instruction set is mostly arithmetic.
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A few instructions have variants that take immediate operands (e.g.,
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:inst:`and` / :inst:`and_imm`), but in general an instruction is required to
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load a constant into an SSA value.
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Special operations
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------------------
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.. inst:: a = iconst n
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.. inst:: a = iconst N
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Integer constant.
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.. inst:: a = fconst n
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Create a scalar integer SSA value with an immediate constant value, or an
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integer vector where all the lanes have the same value.
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.. inst:: a = fconst N
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Floating point constant.
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.. inst:: a = vconst n
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Create a :type:`f32` or :type:`f64` SSA value with an immediate constant
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value, or a floating point vector where all the lanes have the same value.
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.. inst:: a = vconst N
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Vector constant (floating point or integer).
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Create a SIMD vector value where the lanes don't have to be identical.
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.. inst:: a = select c, x, y
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Conditional select.
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@@ -680,12 +689,13 @@ Vector operations
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Integer operations
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------------------
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.. inst:: a = icmp cond, x, y
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.. inst:: a = icmp Cond, x, y
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Integer comparison.
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:param cond: Condition code determining how ``x`` and ``y`` are compared.
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:param x, y: Integer scalar or vector values of the same type.
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:arg Cond: Condition code determining how ``x`` and ``y`` are compared.
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:arg x: First value to compare.
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:arg y: Second value to compare.
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:rtype: :type:`bool` or :type:`boolxN` with the same number of lanes as
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``x`` and ``y``.
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@@ -708,29 +718,59 @@ Integer operations
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Wrapping integer addition: :math:`a := x + y \pmod{2^B}`. This instruction
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does not depend on the signed/unsigned interpretation of the operands.
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Polymorphic over all integer types (vector and scalar).
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.. inst:: a = iadd_imm x, Imm
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Add immediate integer.
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Same as :inst:`iadd`, but one operand is an immediate constant.
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:arg iN x: Dynamic addend.
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:arg Imm: Immediate addend.
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Polymorphic over all scalar integer types.
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.. inst:: a = isub x, y
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Wrapping integer subtraction: :math:`a := x - y \pmod{2^B}`. This
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instruction does not depend on the signed/unsigned interpretation of the
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operands.
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.. todo:: Overflow arithmetic
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Polymorphic over all integer types (vector and scalar).
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.. inst:: a = isub_imm Imm, x
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Immediate subtraction.
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Also works as integer negation when :math:`Imm = 0`. Use :inst:`iadd_imm` with a
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negative immediate operand for the reverse immediate subtraction.
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:arg Imm: Immediate minuend.
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:arg iN x: Dynamic subtrahend.
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Polymorphic over all scalar integer types.
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.. todo:: Integer overflow arithmetic
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Add instructions for add with carry out / carry in and so on. Enough to
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implement larger integer types efficiently. It should also be possible to
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legalize :type:`i64` arithmetic to terms of :type:`i32` operations.
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.. inst:: a = ineg x
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Wrapping integer negation: :math:`a := -x \pmod{2^B}`. This instruction does
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not depend on the signed/unsigned interpretation of the operand.
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.. inst:: a = imul x, y
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Wrapping integer multiplication: :math:`a := x y \pmod{2^B}`. This
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instruction does not depend on the signed/unsigned interpretation of the
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operands.
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Polymorphic over all integer types (vector and scalar).
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.. inst:: a = imul_imm x, Imm
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Integer multiplication by immediate constant.
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Polymorphic over all scalar integer types.
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.. todo:: Larger multiplication results.
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For example, ``smulx`` which multiplies :type:`i32` operands to produce a
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@@ -741,10 +781,11 @@ Integer operations
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Unsigned integer division: :math:`a := \lfloor {x \over y} \rfloor`. This
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operation traps if the divisor is zero.
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.. todo::
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Add a ``udiv_imm`` variant with an immediate divisor greater than 1.
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This is useful for pattern-matching divide-by-constant, and this
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instruction would be non-trapping.
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.. inst:: a = udiv_imm x, Imm
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Unsigned integer division by an immediate constant.
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This instruction never traps because a divisor of zero is not allowed.
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.. inst:: a = sdiv x, y
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@@ -753,37 +794,52 @@ Integer operations
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the result is not representable in :math:`B` bits two's complement. This only
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happens when :math:`x = -2^{B-1}, y = -1`.
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.. todo::
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Add a ``sdiv_imm`` variant with an immediate non-zero divisor. This is
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useful for pattern-matching divide-by-constant, and this instruction
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would be non-trapping. Don't allow divisors 0, 1, or -1.
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.. inst:: a = sdiv_imm x, Imm
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Signed integer division by an immediate constant.
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This instruction never traps because a divisor of -1 or 0 is not allowed.
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.. inst:: a = urem x, y
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Unsigned integer remainder. This operation traps if the divisor is zero.
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Unsigned integer remainder.
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.. todo::
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Add a ``urem_imm`` non-trapping variant.
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This operation traps if the divisor is zero.
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.. inst:: a = urem_imm x, Imm
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Unsigned integer remainder with immediate divisor.
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This instruction never traps because a divisor of zero is not allowed.
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.. inst:: a = srem x, y
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Signed integer remainder. This operation traps if the divisor is zero.
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Signed integer remainder.
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This operation traps if the divisor is zero.
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.. todo:: Integer remainder vs modulus.
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.. todo::
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Clarify whether the result has the sign of the divisor or the dividend.
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Should we add a ``smod`` instruction for the case where the result has
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the same sign as the divisor?
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.. inst:: a = srem_imm x, Imm
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Signed integer remainder with immediate divisor.
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This instruction never traps because a divisor of 0 or -1 is not allowed.
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.. todo:: Minimum / maximum.
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NEON has ``smin``, ``smax``, ``umin``, and ``umax`` instructions. We should
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replicate those for both scalar and vector integer types. Even if the
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target ISA doesn't have scalar operations, these are good pattern mtching
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target ISA doesn't have scalar operations, these are good pattern matching
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targets.
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.. todo:: Saturating arithmetic.
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Mostly for SIMD use, but again these are good paterns to contract.
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Mostly for SIMD use, but again these are good patterns for contraction.
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Something like ``usatadd``, ``usatsub``, ``ssatadd``, and ``ssatsub`` is a
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good start.
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@@ -825,9 +881,9 @@ Bitwise operations
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Rotate the bits in ``x`` by ``y`` places.
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:param x: Integer value to be rotated.
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:param y: Number of bits to shift. Any integer type, not necessarily the
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same type as ``x``.
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:arg T x: Integer value to be rotated.
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:arg iN y: Number of bits to shift. Any scalar integer type, not necessarily
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the same type as ``x``.
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:rtype: Same type as ``x``.
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.. inst:: a = rotr x, y
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@@ -836,9 +892,9 @@ Bitwise operations
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Rotate the bits in ``x`` by ``y`` places.
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:param x: Integer value to be rotated.
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:param y: Number of bits to shift. Any integer type, not necessarily the
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same type as ``x``.
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:arg T x: Integer value to be rotated.
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:arg iN y: Number of bits to shift. Any scalar integer type, not necessarily
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the same type as ``x``.
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:rtype: Same type as ``x``.
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.. inst:: a = ishl x, y
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@@ -848,9 +904,9 @@ Bitwise operations
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The shift amount is masked to the size of ``x``.
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:param x: Integer value to be shifted.
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:param y: Number of bits to shift. Any integer type, not necessarily the
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same type as ``x``.
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:arg T x: Integer value to be shifted.
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:arg iN y: Number of bits to shift. Any scalar integer type, not necessarily
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the same type as ``x``.
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:rtype: Same type as ``x``.
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When shifting a B-bits integer type, this instruction computes:
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@@ -868,9 +924,9 @@ Bitwise operations
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The shift amount is masked to the size of the register.
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:param x: Integer value to be shifted.
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:param y: Number of bits to shift. Can be any integer type, not necessarily
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the same type as ``x``.
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:arg T x: Integer value to be shifted.
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:arg iN y: Number of bits to shift. Can be any scalar integer type, not
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necessarily the same type as ``x``.
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:rtype: Same type as ``x``.
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When shifting a B-bits integer type, this instruction computes:
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@@ -888,9 +944,9 @@ Bitwise operations
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The shift amount is masked to the size of the register.
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:param x: Integer value to be shifted.
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:param y: Number of bits to shift. Can be any integer type, not necessarily
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the same type as ``x``.
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:arg T x: Integer value to be shifted.
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:arg iN y: Number of bits to shift. Can be any scalar integer type, not
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necessarily the same type as ``x``.
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:rtype: Same type as ``x``.
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.. todo:: Add ``sshr_imm`` variant with an immediate ``y``.
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@@ -899,7 +955,7 @@ Bitwise operations
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Count leading zero bits.
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:param x: Integer value.
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:arg x: Integer value.
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:rtype: :type:`i8`
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Starting from the MSB in ``x``, count the number of zero bits before
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@@ -910,7 +966,7 @@ Bitwise operations
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Count leading sign bits.
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:param x: Integer value.
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:arg x: Integer value.
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:rtype: :type:`i8`
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Starting from the MSB after the sign bit in ``x``, count the number of
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@@ -921,7 +977,7 @@ Bitwise operations
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Count trailing zeros.
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:param x: Integer value.
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:arg x: Integer value.
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:rtype: :type:`i8`
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Starting from the LSB in ``x``, count the number of zero bits before
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@@ -932,7 +988,7 @@ Bitwise operations
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Population count
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:param x: Integer value.
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:arg x: Integer value.
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:rtype: :type:`i8`
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Count the number of one bits in ``x``.
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@@ -941,12 +997,14 @@ Bitwise operations
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Floating point operations
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-------------------------
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.. inst:: a = fcmp cond, x, y
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These operations generally follow IEEE 754-2008 semantics.
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.. inst:: a = fcmp Cond, x, y
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Floating point comparison.
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:param cond: Condition code determining how ``x`` and ``y`` are compared.
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:param x, y: Floating point scalar or vector values of the same type.
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:arg Cond: Condition code determining how ``x`` and ``y`` are compared.
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:arg x,y: Floating point scalar or vector values of the same type.
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:rtype: :type:`bool` or :type:`boolxN` with the same number of lanes as
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``x`` and ``y``.
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@@ -978,7 +1036,7 @@ Floating point operations
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Floating point negation.
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:returns: ``x`` with its sign bit inverted.
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:result: ``x`` with its sign bit inverted.
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Note that this is a pure bitwise operation.
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@@ -986,7 +1044,7 @@ Floating point operations
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Floating point absolute value.
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:returns: ``x`` with its sign bit cleared.
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:result: ``x`` with its sign bit cleared.
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Note that this is a pure bitwise operation.
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@@ -994,18 +1052,19 @@ Floating point operations
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Floating point copy sign.
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:returns: ``x`` with its sign changed to that of ``y``.
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:result: ``x`` with its sign changed to that of ``y``.
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Note that this is a pure bitwise operation. The sign bit from ``y`` is
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copied to the sign bit of ``x``.
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.. inst:: fmul x, y
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.. inst:: fdiv x, y
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.. inst:: fmin x, y
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.. inst:: fminnum x, y
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.. inst:: fmax x, y
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.. inst:: fmaxnum x, y
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.. inst:: ceil x
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.. inst:: a = fmul x, y
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.. inst:: a = fdiv x, y
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.. inst:: a = fmin x, y
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.. inst:: a = fminnum x, y
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.. inst:: a = fmax x, y
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.. inst:: a = fmaxnum x, y
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.. inst:: a = ceil x
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Round floating point round to integral, towards positive infinity.
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@@ -1053,6 +1112,7 @@ Conversion operations
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.. inst:: a = cvt_utof x
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.. inst:: a = cvt_stof x
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Glossary
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========
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