[wwwdocs][committed] Update vectorizer's webpage

[wwwdocs][committed] Update vectorizer's webpage

[Ira Rosen]

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Hi,

I committed the attached update.

Ira

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? yy
cvs diff: Diffing .
Index: vectorization.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/projects/tree-ssa/vectorization.html,v
retrieving revision 1.27
diff -r1.27 vectorization.html
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<     <p>The goal of this project is to develop a loop vectorizer in
<     GCC, based on the <a href="./">tree-ssa</a> framework. This
<     work is taking place in the autovect-branch, and is merged periodically
<     to mainline.</p>
---
>     <p>The goal of this project is to develop a loop and basic block vectorizer in
>     GCC, based on the <a href="./">tree-ssa</a> framework.</p>
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>   <dt>2011-10-23</dt>
>      <dd>
>      <ol>
>         <li>Vectorization of reduction in loop SLP.
>             Both <a href="#slp-reduc-2"> multiple reduction cycles</a> and 
>             <a href="#slp-reduc-1"> reduction chains</a> are supported. </li>
>         <li>Various <a href="#slp"> basic block vectorization (SLP)</a>
>             improvements, such as
>             better data dependence analysis, support of misaligned accesses
>             and multiple types, cost model.</li>
>         <li>Detection of vector size:
>             <a href= "http://gcc.gnu.org/ml/gcc-patches/2010-10/msg00441.html">
>             http://gcc.gnu.org/ml/gcc-patches/2010-10/msg00441.html</a>.</li>
>         <li>Vectorization of loads with <a href="#negative"> negative step</a>.</li>
>         <li>Improved realignment scheme: 
>             <a href= "http://gcc.gnu.org/ml/gcc-patches/2010-06/msg02301.html">
>             http://gcc.gnu.org/ml/gcc-patches/2010-06/msg02301.html</a>.</li>
>         <li>A new built-in, <a href="#assume-aligned">
>             <code>__builtin_assume_aligned</code></a>, has been added,
>             through which the compiler can be hinted about pointer alignment.</li>
>         <li>Support of <a href="#strided"> strided accesses</a> using
>             memory instructions that have
>             the interleaving "built in", such as NEON's vldN and vstN.</li>
>         <li>The vectorizer now attempts to reduce over-promotion of operands in some vector
>             operations: <a href= "http://gcc.gnu.org/ml/gcc-patches/2011-07/msg01472.html">
>             http://gcc.gnu.org/ml/gcc-patches/2011-07/msg01472.html</a>.</li>
>         <li><a href="#widen-shift"> Widening shifts</a> are now detected and vectorized
>             if supported by the target.</li>
>         <li>Vectorization of conditions with <a href="#cond-mix"> mixed types</a>.</li>
>         <li>Support of loops with <a href="#bool"> bool</a>.</li>
>     </ol>
>     </dd>
> </dl>
> 
> <dl>
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<             other then reduction cycles in nested loops) (2009-06-16)</li>
---
>             other than reduction cycles in nested loops) (2009-06-16)</li>
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<     to this project include Revital Eres, Richard Guenther, and Ira Rosen.
---
>     to this project include Revital Eres, Richard Guenther, Jakub Jelinek, Michael Matz,
>     Richard Sandiford, and Ira Rosen.
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< <strong>example11</strong>: 
---
> <a name="strided"><strong>example11</strong>:</a>
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<  
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< 
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< 
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< 
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> </pre>
> 
> <a name="slp-reduc-2"><strong>example18</strong>: Simple reduction in SLP:</a>
> <pre>
> int sum1;
> int sum2;
> int a[128];
> void foo (void)
> {
>   int i;
> 
>   for (i = 0; i &lt; 64; i++)
>     {
>       sum1 += a[2*i];
>       sum2 += a[2*i+1];
>     }
> }
> </pre>
> 
> <a name="slp-reduc-1"><strong>example19</strong>: Reduction chain in SLP:</a>
> <pre>
> int sum;
> int a[128];
> void foo (void)
> {
>   int i;
> 
>   for (i = 0; i &lt; 64; i++)
>     {
>       sum += a[2*i];
>       sum += a[2*i+1];
>     }
> }
> </pre>
> 
> <a name="slp"><strong>example20</strong>: Basic block SLP with
> multiple types, loads with different offsets, misaligned load,
> and not-affine accesses:</a>
> <pre>
> void foo (int * __restrict__ dst, short * __restrict__ src,
>           int h, int stride, short A, short B)
> {
>   int i;
>   for (i = 0; i &lt; h; i++)
>     {
>       dst[0] += A*src[0] + B*src[1];
>       dst[1] += A*src[1] + B*src[2];
>       dst[2] += A*src[2] + B*src[3];
>       dst[3] += A*src[3] + B*src[4];
>       dst[4] += A*src[4] + B*src[5];
>       dst[5] += A*src[5] + B*src[6];
>       dst[6] += A*src[6] + B*src[7];
>       dst[7] += A*src[7] + B*src[8];
>       dst += stride;
>       src += stride;
>     }
> }
> </pre>
> 
> <a name="negative"><strong>example21</strong>: Backward access:</a>
> <pre>
> int foo (int *b, int n)
> {
>   int i, a = 0;
> 
>   for (i = n-1; i &ge; 0; i--)
>     a += b[i];
> 
>   return a;
> }
> </pre>
> 
> <a name="assume-aligned"><strong>example22</strong>: Alignment hints:</a>
> <pre>
> void foo (int *out1, int *in1, int *in2, int n)
> {
>   int i;
> 
>   out1 = __builtin_assume_aligned (out1, 32, 16);
>   in1 = __builtin_assume_aligned (in1, 32, 16);
>   in2 = __builtin_assume_aligned (in2, 32, 0);
> 
>   for (i = 0; i &lt; n; i++)
>     out1[i] = in1[i] * in2[i];
> }
> </pre>
> 
> <a name="widen-shift"><strong>example23</strong>: Widening shift:</a>
> <pre>
> void foo (unsigned short *src, unsigned int *dst)
> {
>   int i;
> 
>   for (i = 0; i &lt; 256; i++)
>     *dst++ = *src++ &lt;&lt; 7;
> }
> </pre>
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> <a name="cond-mix"><strong>example24</strong>: Condition with mixed types:</a>
> <pre>
> #define N 1024
> float a[N], b[N];
> int c[N];
> 
> void foo (short x, short y)
> {
>   int i;
>   for (i = 0; i &lt; N; i++)
>     c[i] = a[i] &lt; b[i] ? x : y;
> }
> </pre>
> 
> <a name="bool"><strong>example25</strong>: Loop with bool:</a>
> <pre>
> #define N 1024
> float a[N], b[N], c[N], d[N];
> int j[N];
> 
> void foo (void)
> {
>   int i;
>   _Bool x, y;
>   for (i = 0; i &lt; N; i++)
>     {
>       x = (a[i] &lt; b[i]);
>       y = (c[i] &lt; d[i]);
>       j[i] = x &amp; y;
>     }
> }
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>         <li>"Vapor SIMD: Auto-vectorize once, run everywhere",
> 	Dorit Nuzman, Sergei Dyshel, Erven Rohou, Ira Rosen, Kevin Williams,
> 	David Yuste, Albert Cohen, Ayal Zaks, CGO 2011: 151-160</li>
> 
1363c1525
<         <li>"Loop-Aware SLP in GCC - two years later", Ira Rosen, Dorit Nuzman
---
>         <li>"Loop-Aware SLP in GCC", Ira Rosen, Dorit Nuzman