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[Fix, Test] (MG_Backend/DirectGLES, MG_IntegrationTest): a shader writing a buffer texture through an image unit left the CPU shadow stale, so every map and readback after it saw the old bytes

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swung0x48
2026-08-12 17:50:31 -04:00
parent a51c68bb2c
commit 49cb1be0fd
2 changed files with 198 additions and 1 deletions
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MobileGL/MG_Backend/DirectGLES/DirectGLES.cpp
+69
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@@ -17,6 +17,7 @@
#include <MG_Util/Metrics/TextureMetrics.h>
#include <MG_State/GLState/Core.h>
#include <MG_State/GLState/ErrorState/Error.h>
#include <MG_State/GLState/TextureState/TextureObjectBuffer.h>
#include <MG_Impl/GLImpl/Framebuffer/GL_Framebuffer.h>
#include <MG_Util/BackendLoaders/OpenGL/Loader.h>
#include <MG_Util/Converters/GLToStr/GLEnumConverter.h>
@@ -1326,11 +1327,47 @@ namespace MobileGL::MG_Backend::DirectGLES {
backendTarget == TextureTarget::Texture2DMultisampleArray;
}
// Which image units currently hold a WRITABLE buffer texture, and how many. Kept here
// rather than recomputed per draw because the frontend tracks 192 image units and
// almost every program uses none of them: the draw path pays one integer test.
//
// Maintained by SyncImageTextureBinding, which is the single funnel for an image-unit
// change on this backend - glBindImageTextures is a frontend loop over
// glBindImageTexture, and the whole-sweep SyncImageTextureBindings goes through it too.
// Anything that clears a binding WITHOUT coming through here (a deleted texture, a
// recreated context) can only leave a bit set for a unit that no longer has one; the
// sweep re-reads the binding, finds nothing to mark, and CLEARS the bit on its way past.
// So the error is self-healing, and in the direction that costs one wasted look rather
// than one missed write.
static Array<Bool, MG_State::GLState::TextureState::MAX_TEXTURE_IMAGE_UNITS>
g_writableImageBufferUnits{};
static Uint g_writableImageBufferUnitCount = 0;
static Bool IsWritableImageBufferTexture(const MG_State::GLState::ImageTextureBinding& binding) {
return binding.Texture != nullptr && binding.Access != GL_READ_ONLY &&
binding.Texture->GetStorageType() == TextureStorageType::Buffer;
}
static void TrackWritableImageBufferUnit(Uint unit, Bool writableBufferTexture) {
Bool& tracked = g_writableImageBufferUnits[unit];
if (tracked == writableBufferTexture) return;
tracked = writableBufferTexture;
// Written as two guarded steps rather than one signed add: the count is unsigned,
// and a decrement that ever ran one time too many would not saturate at zero, it
// would wrap to four billion and defeat the early-out for the rest of the process.
if (writableBufferTexture) {
++g_writableImageBufferUnitCount;
} else if (g_writableImageBufferUnitCount > 0) {
--g_writableImageBufferUnitCount;
}
}
void SyncImageTextureBinding(Uint unit) {
#ifdef TRACY_ENABLE
ZoneScopedC(TRACY_ZONECOLOR_BACKEND);
#endif
auto& imageBinding = MG_State::pGLContext->GetImageTextureBinding(static_cast<Int>(unit));
TrackWritableImageBufferUnit(unit, IsWritableImageBufferTexture(imageBinding));
if (!imageBinding.Texture) {
g_GLESFuncs.glBindImageTexture(unit, 0, 0, GL_FALSE, 0, GL_READ_ONLY, GL_RGBA8);
return;
@@ -1343,6 +1380,34 @@ namespace MobileGL::MG_Backend::DirectGLES {
layered, imageBinding.Layer, imageBinding.Access, imageBinding.Format);
}
// A buffer texture bound to a WRITABLE image unit is a buffer the shader is about to
// write, and those writes land in the ES driver's buffer object - behind the frontend's
// CPU shadow, which is what MapBuffer and GetBufferSubData read. Same flag, and for the
// same reason, as MarkShaderStorageBuffersGpuWritten does for a storage block; the
// difference is only which binding the shader reaches the buffer through. A GL_READ_ONLY
// binding is left alone: marking it would make the next map wait on - and then re-read -
// a dispatch that could not have changed a byte of it.
//
// Called from the draw and dispatch preparations rather than from the eager sync
// glBindImageTexture performs: that one runs before any shader has touched the buffer,
// and flagging there would pull the driver's copy over a shadow the application may
// still be writing into.
void MarkWritableImageBufferTexturesGpuWritten() {
if (g_writableImageBufferUnitCount == 0) return;
for (Uint unit = 0; unit < g_writableImageBufferUnits.size(); ++unit) {
if (!g_writableImageBufferUnits[unit]) continue;
const auto& imageBinding = MG_State::pGLContext->GetImageTextureBinding(static_cast<Int>(unit));
if (!IsWritableImageBufferTexture(imageBinding)) {
TrackWritableImageBufferUnit(unit, false);
continue;
}
auto* textureBuffer =
static_cast<MG_State::GLState::TextureObjectBuffer*>(imageBinding.Texture.get());
const auto& bufferObject = textureBuffer->GetBufferBindingSlot().GetBoundObject();
if (bufferObject) bufferObject->MarkGpuWritten();
}
}
void SyncImageTextureBindings() {
#ifdef TRACY_ENABLE
ZoneScopedC(TRACY_ZONECOLOR_BACKEND);
@@ -2258,6 +2323,9 @@ namespace MobileGL::MG_Backend::DirectGLES {
syncBit & DrawSyncBit::IndirectBuffer);
VertexArrayImpl::SyncCurrentVAO(currentVAO, vaoTwin);
TextureImpl::SyncNeccessaryTextures(textureKeys);
// A draw writes through its image units too - the conformance case that found this
// stores into a buffer texture from the FRAGMENT stage, not from a dispatch.
TextureImpl::MarkWritableImageBufferTexturesGpuWritten();
FramebufferImpl::SyncCurrentFBO();
PrgramImpl::SyncCurrentProgram(currentProgram);
RenderStateImpl::SyncRenderState();
@@ -3116,6 +3184,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
BufferImpl::SyncComputeBuffers(includeDispatchIndirectBuffer);
TextureImpl::SyncNeccessaryTextures(textureKeys);
TextureImpl::SyncImageTextureBindings();
TextureImpl::MarkWritableImageBufferTexturesGpuWritten();
PrgramImpl::SyncCurrentProgram(currentProgram);
if (!currentProgram || !currentProgram->GetLinkStatus() || !currentProgram->GetSpirvStatus()) {