forked from OSchip/llvm-project
[Docs] Documentation for the saturation addition and subtraction intrinsics
Differential Revision: https://reviews.llvm.org/D54729 llvm-svn: 347334
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Leonard Chan
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@ -12576,6 +12576,206 @@ Examples:
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%obit = extractvalue {i32, i1} %res, 1
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br i1 %obit, label %overflow, label %normal
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Saturation Arithmetic Intrinsics
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---------------------------------
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Saturation arithmetic is a version of arithmetic in which operations are
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limited to a fixed range between a minimum and maximum value. If the result of
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an operation is greater than the maximum value, the result is set (or
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"clamped") to this maximum. If it is below the minimum, it is clamped to this
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minimum.
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'``llvm.sadd.sat.*``' Intrinsics
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Syntax
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"""""""
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This is an overloaded intrinsic. You can use ``llvm.sadd.sat``
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on any integer bit width or vectors of integers.
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::
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declare i16 @llvm.sadd.sat.i16(i16 %a, i16 %b)
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declare i32 @llvm.sadd.sat.i32(i32 %a, i32 %b)
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declare i64 @llvm.sadd.sat.i64(i64 %a, i64 %b)
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declare <4 x i32> @llvm.sadd.sat.v4i32(<4 x i32> %a, <4 x i32> %b)
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Overview
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"""""""""
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The '``llvm.sadd.sat``' family of intrinsic functions perform signed
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saturation addition on the 2 arguments.
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Arguments
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""""""""""
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The arguments (%a and %b) and the result may be of integer types of any bit
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width, but they must have the same bit width. ``%a`` and ``%b`` are the two
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values that will undergo signed addition.
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Semantics:
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""""""""""
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The maximum value this operation can clamp to is the largest signed value
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representable by the bit width of the arguments. The minimum value is the
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smallest signed value representable by this bit width.
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Examples
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"""""""""
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.. code-block:: llvm
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%res = call i4 @llvm.sadd.sat.i4(i4 1, i4 2) ; %res = 3
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%res = call i4 @llvm.sadd.sat.i4(i4 5, i4 6) ; %res = 7
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%res = call i4 @llvm.sadd.sat.i4(i4 -4, i4 2) ; %res = -2
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%res = call i4 @llvm.sadd.sat.i4(i4 -4, i4 -5) ; %res = -8
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'``llvm.uadd.sat.*``' Intrinsics
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Syntax
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"""""""
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This is an overloaded intrinsic. You can use ``llvm.uadd.sat``
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on any integer bit width or vectors of integers.
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::
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declare i16 @llvm.uadd.sat.i16(i16 %a, i16 %b)
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declare i32 @llvm.uadd.sat.i32(i32 %a, i32 %b)
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declare i64 @llvm.uadd.sat.i64(i64 %a, i64 %b)
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declare <4 x i32> @llvm.uadd.sat.v4i32(<4 x i32> %a, <4 x i32> %b)
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Overview
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"""""""""
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The '``llvm.uadd.sat``' family of intrinsic functions perform unsigned
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saturation addition on the 2 arguments.
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Arguments
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""""""""""
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The arguments (%a and %b) and the result may be of integer types of any bit
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width, but they must have the same bit width. ``%a`` and ``%b`` are the two
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values that will undergo unsigned addition.
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Semantics:
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""""""""""
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The maximum value this operation can clamp to is the largest unsigned value
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representable by the bit width of the arguments. Because this is an unsigned
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operation, the result will never saturate towards zero.
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Examples
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"""""""""
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.. code-block:: llvm
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%res = call i4 @llvm.uadd.sat.i4(i4 1, i4 2) ; %res = 3
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%res = call i4 @llvm.uadd.sat.i4(i4 5, i4 6) ; %res = 11
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%res = call i4 @llvm.uadd.sat.i4(i4 8, i4 8) ; %res = 15
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'``llvm.ssub.sat.*``' Intrinsics
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Syntax
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"""""""
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This is an overloaded intrinsic. You can use ``llvm.ssub.sat``
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on any integer bit width or vectors of integers.
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::
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declare i16 @llvm.ssub.sat.i16(i16 %a, i16 %b)
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declare i32 @llvm.ssub.sat.i32(i32 %a, i32 %b)
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declare i64 @llvm.ssub.sat.i64(i64 %a, i64 %b)
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declare <4 x i32> @llvm.ssub.sat.v4i32(<4 x i32> %a, <4 x i32> %b)
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Overview
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"""""""""
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The '``llvm.ssub.sat``' family of intrinsic functions perform signed
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saturation subtraction on the 2 arguments.
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Arguments
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""""""""""
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The arguments (%a and %b) and the result may be of integer types of any bit
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width, but they must have the same bit width. ``%a`` and ``%b`` are the two
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values that will undergo signed subtraction.
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Semantics:
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""""""""""
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The maximum value this operation can clamp to is the largest signed value
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representable by the bit width of the arguments. The minimum value is the
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smallest signed value representable by this bit width.
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Examples
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"""""""""
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.. code-block:: llvm
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%res = call i4 @llvm.ssub.sat.i4(i4 2, i4 1) ; %res = 1
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%res = call i4 @llvm.ssub.sat.i4(i4 2, i4 6) ; %res = -4
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%res = call i4 @llvm.ssub.sat.i4(i4 -4, i4 5) ; %res = -8
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%res = call i4 @llvm.ssub.sat.i4(i4 4, i4 -5) ; %res = 7
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'``llvm.usub.sat.*``' Intrinsics
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Syntax
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"""""""
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This is an overloaded intrinsic. You can use ``llvm.usub.sat``
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on any integer bit width or vectors of integers.
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::
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declare i16 @llvm.usub.sat.i16(i16 %a, i16 %b)
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declare i32 @llvm.usub.sat.i32(i32 %a, i32 %b)
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declare i64 @llvm.usub.sat.i64(i64 %a, i64 %b)
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declare <4 x i32> @llvm.usub.sat.v4i32(<4 x i32> %a, <4 x i32> %b)
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Overview
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"""""""""
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The '``llvm.usub.sat``' family of intrinsic functions perform unsigned
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saturation subtraction on the 2 arguments.
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Arguments
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""""""""""
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The arguments (%a and %b) and the result may be of integer types of any bit
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width, but they must have the same bit width. ``%a`` and ``%b`` are the two
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values that will undergo unsigned subtraction.
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Semantics:
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""""""""""
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The minimum value this operation can clamp to is 0, which is the smallest
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unsigned value representable by the bit width of the unsigned arguments.
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Because this is an unsigned operation, the result will never saturate towards
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the largest possible value representable by this bit width.
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Examples
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"""""""""
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.. code-block:: llvm
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%res = call i4 @llvm.usub.sat.i4(i4 2, i4 1) ; %res = 1
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%res = call i4 @llvm.usub.sat.i4(i4 2, i4 6) ; %res = 0
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Specialised Arithmetic Intrinsics
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---------------------------------
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