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Added note on how the WinCE scalers are wasting valuable cycles, and how to fix that

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svn-id: r31241
This commit is contained in:
Max Horn 2008-03-26 11:09:38 +00:00
parent 52930616c6
commit 53ea302f5d
1 changed files with 14 additions and 0 deletions
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14
backends/platform/wince/CEScaler.cpp
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@ -37,6 +37,16 @@ void initCEScaler(void) {
maskUsed = 1;
}
// FIXME: Fingolfin says: The following interpolation code is a lot slower than it needs
// to be. The reason: Using the value of a global variable to index two global arrays is
// extremly difficult if not impossible for the compiler to optimize. At the very least,
// the two arrays should be 'static const', but even then, memory access is required.
// To avoid this, one could use the techniques used by our other scalers. See also the
// interpolate functions in graphics/scaler/intern.h.
// Even if those can't be used directly for some reasons (e.g. the compiler has problems
// with templates), then still the *techniques* could and should be used. I would exepct
// that this way, even the C version of PocketPCPortrait() should get a big speed boost.
static inline uint16 CEinterpolate16_4(uint16 p1, uint16 p2, uint16 p3, uint16 p4)
{
return ((((p1 & redblueMasks[maskUsed]) + (p2 & redblueMasks[maskUsed]) + (p3 & redblueMasks[maskUsed]) + (p4 & redblueMasks[maskUsed])) / 4) & redblueMasks[maskUsed]) |
@ -74,6 +84,10 @@ void PocketPCPortrait(const uint8 *srcPtr, uint32 srcPitch, uint8 *dstPtr, uint3
}
}
// FIXME: Fingolfin says: Please document this function. What does it compute? How
// does it differ from the code in aspect.cpp ? It would be nice to speed up this function
// here using the ideas and tracks from aspect.cpp and the comment above, as right now, it
// is rather hard for the compiler to optimize this code properly.
void PocketPCLandscapeAspect(const uint8 *srcPtr, uint32 srcPitch, uint8 *dstPtr, uint32 dstPitch, int width, int height) {
#define RB(x) ((x & redblueMasks[maskUsed])<<8)