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BPStructs: Gracefully handle out-of-range EFB copies

Since the copy X and Y coordinates/sizes are 10-bit, the game can configure a
copy region up to 1024x1024. Hardware tests have found that the number of bytes
written does not depend on the configured stride, instead it is based on the
size registers, writing beyond the length  of a single row. The data written
for the pixels which lie outside the EFB bounds does not wrap around instead
returning different colors based on the pixel format of the EFB.

This suggests it's not based on coordinates, but instead on memory addresses.
The effect of a within-bounds size but out-of-bounds offset
(e.g. offset 320,0, size 640,480) are the same.

As it would be difficult to emulate the exact behavior of out-of-bounds reads,
instead of writing the junk data, we don't write anything to RAM at all for
over-sized copies, and clamp to the EFB borders for over-offset copies.
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stenzek committed Mar 31, 2019
1 parent 3e544f9 commit 378b605669641ec9675e137d04f4037bc621cd46
Showing with 37 additions and 6 deletions.
  1. +37 −6 Source/Core/VideoCommon/BPStructs.cpp
@@ -225,13 +225,44 @@ static void BPWritten(const BPCmd& bp)

// Here Width+1 like Height, otherwise some textures are corrupted already since the native
// resolution.
// TODO: What's the behavior of out of bound access?
srcRect.right = static_cast<int>(bpmem.copyTexSrcXY.x + bpmem.copyTexSrcWH.x + 1);
srcRect.bottom = static_cast<int>(bpmem.copyTexSrcXY.y + bpmem.copyTexSrcWH.y + 1);

UPE_Copy PE_copy = bpmem.triggerEFBCopy;
// Since the copy X and Y coordinates/sizes are 10-bit, the game can configure a copy region up
// to 1024x1024. Hardware tests have found that the number of bytes written does not depend on
// the configured stride, instead it is based on the size registers, writing beyond the length
// of a single row. The data written for the pixels which lie outside the EFB bounds does not
// wrap around instead returning different colors based on the pixel format of the EFB. This
// suggests it's not based on coordinates, but instead on memory addresses. The effect of a
// within-bounds size but out-of-bounds offset (e.g. offset 320,0, size 640,480) are the same.

// As it would be difficult to emulate the exact behavior of out-of-bounds reads, instead of
// writing the junk data, we don't write anything to RAM at all for over-sized copies, and clamp
// to the EFB borders for over-offset copies. The arcade virtual console games (e.g. 1942) are
// known for configuring these out-of-range copies.
int copy_width = srcRect.GetWidth();
int copy_height = srcRect.GetHeight();
if (srcRect.right > EFB_WIDTH || srcRect.bottom > EFB_HEIGHT)
{
WARN_LOG(VIDEO, "Oversized EFB copy: %dx%d (offset %d,%d stride %u)", copy_width, copy_height,
srcRect.left, srcRect.top, destStride);

// Adjust the copy size to fit within the EFB. So that we don't end up with a stretched image,
// instead of clamping the source rectangle, we reduce it by the over-sized amount.
if (copy_width > EFB_WIDTH)
{
srcRect.right -= copy_width - EFB_WIDTH;
copy_width = EFB_WIDTH;
}
if (copy_height > EFB_HEIGHT)
{
srcRect.bottom -= copy_height - EFB_HEIGHT;
copy_height = EFB_HEIGHT;
}
}

// Check if we are to copy from the EFB or draw to the XFB
const UPE_Copy PE_copy = bpmem.triggerEFBCopy;
if (PE_copy.copy_to_xfb == 0)
{
// bpmem.zcontrol.pixel_format to PEControl::Z24 is when the game wants to copy from ZBuffer
@@ -240,8 +271,8 @@ static void BPWritten(const BPCmd& bp)
{0, 0, 21, 22, 21, 0, 0}};
bool is_depth_copy = bpmem.zcontrol.pixel_format == PEControl::Z24;
g_texture_cache->CopyRenderTargetToTexture(
destAddr, PE_copy.tp_realFormat(), srcRect.GetWidth(), srcRect.GetHeight(), destStride,
is_depth_copy, srcRect, !!PE_copy.intensity_fmt, !!PE_copy.half_scale, 1.0f, 1.0f,
destAddr, PE_copy.tp_realFormat(), copy_width, copy_height, destStride, is_depth_copy,
srcRect, !!PE_copy.intensity_fmt, !!PE_copy.half_scale, 1.0f, 1.0f,
bpmem.triggerEFBCopy.clamp_top, bpmem.triggerEFBCopy.clamp_bottom, filter_coefficients);
}
else
@@ -271,8 +302,8 @@ static void BPWritten(const BPCmd& bp)

bool is_depth_copy = bpmem.zcontrol.pixel_format == PEControl::Z24;
g_texture_cache->CopyRenderTargetToTexture(
destAddr, EFBCopyFormat::XFB, srcRect.GetWidth(), height, destStride, is_depth_copy,
srcRect, false, false, yScale, s_gammaLUT[PE_copy.gamma], bpmem.triggerEFBCopy.clamp_top,
destAddr, EFBCopyFormat::XFB, copy_width, height, destStride, is_depth_copy, srcRect,
false, false, yScale, s_gammaLUT[PE_copy.gamma], bpmem.triggerEFBCopy.clamp_top,
bpmem.triggerEFBCopy.clamp_bottom, bpmem.copyfilter.GetCoefficients());

// This stays in to signal end of a "frame"

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