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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Vladimir Serbinenko <phcoder@gmail.com>
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Date: Thu, 26 Feb 2015 21:27:32 +0100
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Subject: [PATCH] jpeg: Optimise by replacing division with shifts.
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(cherry picked from commit 7213c1e02807e760febec06a0f19b11173abc55a)
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---
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grub-core/video/readers/jpeg.c | 25 ++++++++++++++-----------
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1 file changed, 14 insertions(+), 11 deletions(-)
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diff --git a/grub-core/video/readers/jpeg.c b/grub-core/video/readers/jpeg.c
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index 84cf5ceec9..55bd95b797 100644
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--- a/grub-core/video/readers/jpeg.c
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+++ b/grub-core/video/readers/jpeg.c
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@@ -94,7 +94,7 @@ struct grub_jpeg_data
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jpeg_data_unit_t crdu;
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jpeg_data_unit_t cbdu;
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- unsigned vs, hs;
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+ unsigned log_vs, log_hs;
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int dri;
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unsigned r1;
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@@ -321,11 +321,14 @@ grub_jpeg_decode_sof (struct grub_jpeg_data *data)
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ss = grub_jpeg_get_byte (data); /* Sampling factor. */
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if (!id)
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{
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- data->vs = ss & 0xF; /* Vertical sampling. */
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- data->hs = ss >> 4; /* Horizontal sampling. */
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- if ((data->vs > 2) || (data->hs > 2) || (data->vs == 0) || (data->hs == 0))
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+ grub_uint8_t vs, hs;
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+ vs = ss & 0xF; /* Vertical sampling. */
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+ hs = ss >> 4; /* Horizontal sampling. */
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+ if ((vs > 2) || (hs > 2) || (vs == 0) || (hs == 0))
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return grub_error (GRUB_ERR_BAD_FILE_TYPE,
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"jpeg: sampling method not supported");
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+ data->log_vs = (vs == 2);
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+ data->log_hs = (hs == 2);
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}
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else if (ss != JPEG_SAMPLING_1x1)
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return grub_error (GRUB_ERR_BAD_FILE_TYPE,
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@@ -638,10 +641,10 @@ grub_jpeg_decode_data (struct grub_jpeg_data *data)
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unsigned c1, vb, hb, nr1, nc1;
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int rst = data->dri;
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- vb = data->vs * 8;
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- hb = data->hs * 8;
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- nr1 = (data->image_height + vb - 1) / vb;
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- nc1 = (data->image_width + hb - 1) / hb;
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+ vb = 8 << data->log_vs;
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+ hb = 8 << data->log_hs;
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+ nr1 = (data->image_height + vb - 1) >> (3 + data->log_vs);
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+ nc1 = (data->image_width + hb - 1) >> (3 + data->log_hs);
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if (data->bitmap_ptr == NULL)
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return grub_error(GRUB_ERR_BAD_FILE_TYPE,
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@@ -655,8 +658,8 @@ grub_jpeg_decode_data (struct grub_jpeg_data *data)
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unsigned r2, c2, nr2, nc2;
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grub_uint8_t *ptr2;
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- for (r2 = 0; r2 < data->vs; r2++)
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- for (c2 = 0; c2 < data->hs; c2++)
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+ for (r2 = 0; r2 < (1U << data->log_vs); r2++)
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+ for (c2 = 0; c2 < (1U << data->log_hs); c2++)
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grub_jpeg_decode_du (data, 0, data->ydu[r2 * 2 + c2]);
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if (data->color_components >= 3)
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@@ -678,7 +681,7 @@ grub_jpeg_decode_data (struct grub_jpeg_data *data)
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unsigned i0;
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int yy;
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- i0 = (r2 / data->vs) * 8 + (c2 / data->hs);
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+ i0 = (r2 >> data->log_vs) * 8 + (c2 >> data->log_hs);
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yy = data->ydu[(r2 / 8) * 2 + (c2 / 8)][(r2 % 8) * 8 + (c2 % 8)];
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if (data->color_components >= 3)
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