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<title>Vectors (GNU Compiler Collection (GCC) Internals)</title>
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Expression-trees.html#Expression-trees" rel="up" title="Expression trees">
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<a name="Vectors"></a>
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<div class="header">
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<p>
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Previous: <a href="Unary-and-Binary-Expressions.html#Unary-and-Binary-Expressions" accesskey="p" rel="prev">Unary and Binary Expressions</a>, Up: <a href="Expression-trees.html#Expression-trees" accesskey="u" rel="up">Expression trees</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Vectors-1"></a>
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<h4 class="subsection">11.6.4 Vectors</h4>
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<a name="index-VEC_005fDUPLICATE_005fEXPR"></a>
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<a name="index-VEC_005fSERIES_005fEXPR"></a>
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<a name="index-VEC_005fLSHIFT_005fEXPR"></a>
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<a name="index-VEC_005fRSHIFT_005fEXPR"></a>
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<a name="index-VEC_005fWIDEN_005fMULT_005fHI_005fEXPR"></a>
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<a name="index-VEC_005fWIDEN_005fMULT_005fLO_005fEXPR"></a>
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<a name="index-VEC_005fUNPACK_005fHI_005fEXPR"></a>
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<a name="index-VEC_005fUNPACK_005fLO_005fEXPR"></a>
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<a name="index-VEC_005fUNPACK_005fFLOAT_005fHI_005fEXPR"></a>
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<a name="index-VEC_005fUNPACK_005fFLOAT_005fLO_005fEXPR"></a>
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<a name="index-VEC_005fPACK_005fTRUNC_005fEXPR"></a>
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<a name="index-VEC_005fPACK_005fSAT_005fEXPR"></a>
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<a name="index-VEC_005fPACK_005fFIX_005fTRUNC_005fEXPR"></a>
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<a name="index-VEC_005fCOND_005fEXPR"></a>
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<a name="index-SAD_005fEXPR"></a>
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<dl compact="compact">
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<dt><code>VEC_DUPLICATE_EXPR</code></dt>
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<dd><p>This node has a single operand and represents a vector in which every
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element is equal to that operand.
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</p>
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</dd>
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<dt><code>VEC_SERIES_EXPR</code></dt>
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<dd><p>This node represents a vector formed from a scalar base and step,
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given as the first and second operands respectively. Element <var>i</var>
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of the result is equal to ‘<samp><var>base</var> + <var>i</var>*<var>step</var></samp>’.
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</p>
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<p>This node is restricted to integral types, in order to avoid
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specifying the rounding behavior for floating-point types.
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</p>
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</dd>
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<dt><code>VEC_LSHIFT_EXPR</code></dt>
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<dt><code>VEC_RSHIFT_EXPR</code></dt>
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<dd><p>These nodes represent whole vector left and right shifts, respectively.
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The first operand is the vector to shift; it will always be of vector type.
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The second operand is an expression for the number of bits by which to
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shift. Note that the result is undefined if the second operand is larger
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than or equal to the first operand’s type size.
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</p>
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</dd>
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<dt><code>VEC_WIDEN_MULT_HI_EXPR</code></dt>
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<dt><code>VEC_WIDEN_MULT_LO_EXPR</code></dt>
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<dd><p>These nodes represent widening vector multiplication of the high and low
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parts of the two input vectors, respectively. Their operands are vectors
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that contain the same number of elements (<code>N</code>) of the same integral type.
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The result is a vector that contains half as many elements, of an integral type
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whose size is twice as wide. In the case of <code>VEC_WIDEN_MULT_HI_EXPR</code> the
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high <code>N/2</code> elements of the two vector are multiplied to produce the
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vector of <code>N/2</code> products. In the case of <code>VEC_WIDEN_MULT_LO_EXPR</code> the
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low <code>N/2</code> elements of the two vector are multiplied to produce the
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vector of <code>N/2</code> products.
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</p>
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</dd>
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<dt><code>VEC_UNPACK_HI_EXPR</code></dt>
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<dt><code>VEC_UNPACK_LO_EXPR</code></dt>
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<dd><p>These nodes represent unpacking of the high and low parts of the input vector,
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respectively. The single operand is a vector that contains <code>N</code> elements
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of the same integral or floating point type. The result is a vector
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that contains half as many elements, of an integral or floating point type
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whose size is twice as wide. In the case of <code>VEC_UNPACK_HI_EXPR</code> the
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high <code>N/2</code> elements of the vector are extracted and widened (promoted).
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In the case of <code>VEC_UNPACK_LO_EXPR</code> the low <code>N/2</code> elements of the
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vector are extracted and widened (promoted).
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</p>
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</dd>
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<dt><code>VEC_UNPACK_FLOAT_HI_EXPR</code></dt>
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<dt><code>VEC_UNPACK_FLOAT_LO_EXPR</code></dt>
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<dd><p>These nodes represent unpacking of the high and low parts of the input vector,
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where the values are converted from fixed point to floating point. The
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single operand is a vector that contains <code>N</code> elements of the same
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integral type. The result is a vector that contains half as many elements
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of a floating point type whose size is twice as wide. In the case of
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<code>VEC_UNPACK_HI_EXPR</code> the high <code>N/2</code> elements of the vector are
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extracted, converted and widened. In the case of <code>VEC_UNPACK_LO_EXPR</code>
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the low <code>N/2</code> elements of the vector are extracted, converted and widened.
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</p>
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</dd>
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<dt><code>VEC_PACK_TRUNC_EXPR</code></dt>
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<dd><p>This node represents packing of truncated elements of the two input vectors
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into the output vector. Input operands are vectors that contain the same
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number of elements of the same integral or floating point type. The result
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is a vector that contains twice as many elements of an integral or floating
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point type whose size is half as wide. The elements of the two vectors are
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demoted and merged (concatenated) to form the output vector.
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</p>
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</dd>
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<dt><code>VEC_PACK_SAT_EXPR</code></dt>
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<dd><p>This node represents packing of elements of the two input vectors into the
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output vector using saturation. Input operands are vectors that contain
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the same number of elements of the same integral type. The result is a
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vector that contains twice as many elements of an integral type whose size
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is half as wide. The elements of the two vectors are demoted and merged
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(concatenated) to form the output vector.
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</p>
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</dd>
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<dt><code>VEC_PACK_FIX_TRUNC_EXPR</code></dt>
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<dd><p>This node represents packing of elements of the two input vectors into the
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output vector, where the values are converted from floating point
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to fixed point. Input operands are vectors that contain the same number
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of elements of a floating point type. The result is a vector that contains
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twice as many elements of an integral type whose size is half as wide. The
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elements of the two vectors are merged (concatenated) to form the output
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vector.
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</p>
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</dd>
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<dt><code>VEC_COND_EXPR</code></dt>
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<dd><p>These nodes represent <code>?:</code> expressions. The three operands must be
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vectors of the same size and number of elements. The second and third
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operands must have the same type as the entire expression. The first
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operand is of signed integral vector type. If an element of the first
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operand evaluates to a zero value, the corresponding element of the
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result is taken from the third operand. If it evaluates to a minus one
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value, it is taken from the second operand. It should never evaluate to
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any other value currently, but optimizations should not rely on that
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property. In contrast with a <code>COND_EXPR</code>, all operands are always
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evaluated.
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</p>
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</dd>
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<dt><code>SAD_EXPR</code></dt>
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<dd><p>This node represents the Sum of Absolute Differences operation. The three
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operands must be vectors of integral types. The first and second operand
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must have the same type. The size of the vector element of the third
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operand must be at lease twice of the size of the vector element of the
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first and second one. The SAD is calculated between the first and second
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operands, added to the third operand, and returned.
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</p>
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</dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Previous: <a href="Unary-and-Binary-Expressions.html#Unary-and-Binary-Expressions" accesskey="p" rel="prev">Unary and Binary Expressions</a>, Up: <a href="Expression-trees.html#Expression-trees" accesskey="u" rel="up">Expression trees</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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