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Remove the "game uses sequential copies" readback heuristic

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After more than three partial readbacks of one buffer in a frame,
ReadFramebufferToMemory read the whole buffer instead for the rest of the
session, writing rows the game never asked for.

Everybody's Golf 2 reads back four portraits' color and depth per frame, which
turned it on. The whole 480x273 depth buffer then got written to VRAM, and its
last row is where the game keeps its texture heap. A texture header was
overwritten: the portrait showed the scene behind it, and the next time the
portraits were built the game crashed writing through a null pointer.

It was added for speed in Grand Knights History (c42d04829f), which copies many
slivers of a framebuffer, so that game may now do more readbacks.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Henrik RydgårdandClaude Opus 5.5 committed 2026-10-11 14:50:19 +02:00
1 parent 9720041ecf
commit 50696c5b1f
2 files changed
+2 -27
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GPU/Common/FramebufferManagerCommon.cpp
+1 -24
View File
@@ -3445,34 +3445,11 @@ void FramebufferManagerCommon::ReadFramebufferToMemory(VirtualFramebuffer *vfb,
if (x + w >= vfb->bufferWidth) {
w = vfb->bufferWidth - x;
}
if (gameUsesSequentialCopies_) {
// Ignore the x/y/etc., read the entire thing. See below.
x = 0;
y = 0;
w = vfb->width;
h = vfb->height;
vfb->memoryUpdated = true;
vfb->usageFlags |= FB_USAGE_DOWNLOAD;
} else if (x == 0 && y == 0 && w == vfb->width && h == vfb->height) {
if (x == 0 && y == 0 && w == vfb->width && h == vfb->height) {
// Mark it as fully downloaded until next render to it.
if (channel == RASTER_COLOR)
vfb->memoryUpdated = true;
vfb->usageFlags |= FB_USAGE_DOWNLOAD;
} else {
// Let's try to set the flag eventually, if the game copies a lot.
// Some games (like Grand Knights History) copy subranges very frequently.
const static int FREQUENT_SEQUENTIAL_COPIES = 3;
static int frameLastCopy = 0;
static u32 bufferLastCopy = 0;
static int copiesThisFrame = 0;
if (frameLastCopy != gpuStats.totals.numFlips || bufferLastCopy != vfb->fb_address) {
frameLastCopy = gpuStats.totals.numFlips;
bufferLastCopy = vfb->fb_address;
copiesThisFrame = 0;
}
if (++copiesThisFrame > FREQUENT_SEQUENTIAL_COPIES) {
gameUsesSequentialCopies_ = true;
}
}
// This handles any required stretching internally.
GPU/Common/FramebufferManagerCommon.h
+1 -3
View File
@@ -127,7 +127,7 @@ struct VirtualFramebuffer {
// Tracking for downloads-to-CLUT.
u16 clutUpdatedBytes;
// Means that the whole image has already been read back to memory - used when combining small readbacks (gameUsesSequentialCopies_).
// Means that the whole image has already been read back to memory.
bool memoryUpdated;
// TODO: Fold into usageFlags?
@@ -630,8 +630,6 @@ protected:
std::vector<DrawPixelsEntry> drawPixelsCache_;
bool gameUsesSequentialCopies_ = false;
// Sampled in BeginFrame/UpdateSize for safety.
float renderWidth_ = 0.0f;
float renderHeight_ = 0.0f;