On an argument, this attribute indicates that the function does not write
through this pointer argument, even though it may write to the memory that
the pointer points to.
+``argmemonly``
+ This attribute indicates that the only memory accesses inside function are
+ loads and stores from objects pointed to by its pointer-typed arguments,
+ with arbitrary offsets. Or in other words, all memory operations in the
+ function can refer to memory only using pointers based on its function
+ arguments.
+ Note that ``argmemonly`` can be used together with ``readonly`` attribute
+ in order to specify that function reads only from its arguments.
``returns_twice``
This attribute indicates that this function can return twice. The C
``setjmp`` is an example of such a function. The compiler disables
``sc`` instruction on the given subtarget (details vary).
- ``r``, ``d``, ``y``: A 32 or 64-bit GPR register.
- ``f``: A 32 or 64-bit FPU register (``F0-F31``), or a 128-bit MSA register
- (``W0-W31``).
+ (``W0-W31``). In the case of MSA registers, it is recommended to use the ``w``
+ argument modifier for compatibility with GCC.
- ``c``: A 32-bit or 64-bit GPR register suitable for indirect jump (always
``25``).
- ``l``: The ``lo`` register, 32 or 64-bit.
second word of a double-word memory operand. (On a big-endian system, ``D`` is
equivalent to ``L``, and on little-endian system, ``D`` is equivalent to
``M``.)
-- ``w``: No effect.
+- ``w``: No effect. Provided for compatibility with GCC which requires this
+ modifier in order to print MSA registers (``W0-W31``) with the ``f``
+ constraint.
NVPTX:
.. code-block:: llvm
- !0 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 0,
+ !0 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 1,
scope: !3, file: !2, line: 7, type: !3,
flags: DIFlagArtificial)
- !1 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "x", arg: 1,
+ !1 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "x", arg: 2,
scope: !4, file: !2, line: 7, type: !3)
- !1 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "y",
+ !2 = !DILocalVariable(tag: DW_TAG_auto_variable, name: "y",
scope: !5, file: !2, line: 7, type: !3)
DIExpression
Specialised Arithmetic Intrinsics
---------------------------------
+'``llvm.canonicalize.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare float @llvm.canonicalize.f32(float %a)
+ declare double @llvm.canonicalize.f64(double %b)
+
+Overview:
+"""""""""
+
+The '``llvm.canonicalize.*``' intrinsic returns the platform specific canonical
+encoding of a floating point number. This canonicalization is useful for
+implementing certain numeric primitives such as frexp. The canonical encoding is
+defined by IEEE-754-2008 to be:
+
+::
+
+ 2.1.8 canonical encoding: The preferred encoding of a floating-point
+ representation in a format. Applied to declets, significands of finite
+ numbers, infinities, and NaNs, especially in decimal formats.
+
+This operation can also be considered equivalent to the IEEE-754-2008
+conversion of a floating-point value to the same format. NaNs are handled
+according to section 6.2.
+
+Examples of non-canonical encodings:
+
+- x87 pseudo denormals, pseudo NaNs, pseudo Infinity, Unnormals. These are
+ converted to a canonical representation per hardware-specific protocol.
+- Many normal decimal floating point numbers have non-canonical alternative
+ encodings.
+- Some machines, like GPUs or ARMv7 NEON, do not support subnormal values.
+ These are treated as non-canonical encodings of zero and with be flushed to
+ a zero of the same sign by this operation.
+
+Note that per IEEE-754-2008 6.2, systems that support signaling NaNs with
+default exception handling must signal an invalid exception, and produce a
+quiet NaN result.
+
+This function should always be implementable as multiplication by 1.0, provided
+that the compiler does not constant fold the operation. Likewise, division by
+1.0 and ``llvm.minnum(x, x)`` are possible implementations. Addition with
+-0.0 is also sufficient provided that the rounding mode is not -Infinity.
+
+``@llvm.canonicalize`` must preserve the equality relation. That is:
+
+- ``(@llvm.canonicalize(x) == x)`` is equivalent to ``(x == x)``
+- ``(@llvm.canonicalize(x) == @llvm.canonicalize(y))`` is equivalent to
+ to ``(x == y)``
+
+Additionally, the sign of zero must be conserved:
+``@llvm.canonicalize(-0.0) = -0.0`` and ``@llvm.canonicalize(+0.0) = +0.0``
+
+The payload bits of a NaN must be conserved, with two exceptions.
+First, environments which use only a single canonical representation of NaN
+must perform said canonicalization. Second, SNaNs must be quieted per the
+usual methods.
+
+The canonicalization operation may be optimized away if:
+
+- The input is known to be canonical. For example, it was produced by a
+ floating-point operation that is required by the standard to be canonical.
+- The result is consumed only by (or fused with) other floating-point
+ operations. That is, the bits of the floating point value are not examined.
+
'``llvm.fmuladd.*``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
%r2 = call float @llvm.fmuladd.f32(float %a, float %b, float %c) ; yields float:r2 = (a * b) + c
+
+'``llvm.uabsdiff.*``' and '``llvm.sabsdiff.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+This is an overloaded intrinsic. The loaded data is a vector of any integer bit width.
+
+.. code-block:: llvm
+
+ declare <4 x integer> @llvm.uabsdiff.v4i32(<4 x integer> %a, <4 x integer> %b)
+
+
+Overview:
+"""""""""
+
+The ``llvm.uabsdiff`` intrinsic returns a vector result of the absolute difference of the two operands,
+treating them both as unsigned integers.
+
+The ``llvm.sabsdiff`` intrinsic returns a vector result of the absolute difference of the two operands,
+treating them both as signed integers.
+
+.. note::
+
+ These intrinsics are primarily used during the code generation stage of compilation.
+ They are generated by compiler passes such as the Loop and SLP vectorizers.it is not
+ recommended for users to create them manually.
+
+Arguments:
+""""""""""
+
+Both intrinsics take two integer of the same bitwidth.
+
+Semantics:
+""""""""""
+
+The expression::
+
+ call <4 x i32> @llvm.uabsdiff.v4i32(<4 x i32> %a, <4 x i32> %b)
+
+is equivalent to::
+
+ %sub = sub <4 x i32> %a, %b
+ %ispos = icmp ugt <4 x i32> %sub, <i32 -1, i32 -1, i32 -1, i32 -1>
+ %neg = sub <4 x i32> zeroinitializer, %sub
+ %1 = select <4 x i1> %ispos, <4 x i32> %sub, <4 x i32> %neg
+
+Similarly the expression::
+
+ call <4 x i32> @llvm.sabsdiff.v4i32(<4 x i32> %a, <4 x i32> %b)
+
+is equivalent to::
+
+ %sub = sub nsw <4 x i32> %a, %b
+ %ispos = icmp sgt <4 x i32> %sub, <i32 -1, i32 -1, i32 -1, i32 -1>
+ %neg = sub nsw <4 x i32> zeroinitializer, %sub
+ %1 = select <4 x i1> %ispos, <4 x i32> %sub, <4 x i32> %neg
+
+
Half Precision Floating Point Intrinsics
----------------------------------------
projects / oota-llvm.git / blobdiff