commit 3791debc2ba45d54fa87a6b560f0b08ecf46824e
author Sunny Sachanandani <sunnyps@chromium.org> Wed Nov 08 06:24:30 2023 +0000
committer Dawn LUCI CQ <dawn-scoped@luci-project-accounts.iam.gserviceaccount.com> Wed Nov 08 06:24:30 2023 +0000
tree b83e5910e0573152fa9b615ce6e0cc63b63e9114
parent 1e0d0b2827408ec661df5d75befdcbe658d6ab6e

Add toggle for disabling lazy clear for mapped at creation buffers

Add a toggle to skip the memset for clearing mappedAtCreation buffers.
The buffer is considered initialized with this toggle so that we don't
clear it later using the GPU thereby preserving its contents.

Bug: chromium:1456492
Change-Id: I3ec0d2bbcf5b0814e095227836cb7b0d1e983c99
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/159028
Reviewed-by: Austin Eng <enga@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Auto-Submit: Sunny Sachanandani <sunnyps@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>

src/dawn/native/Buffer.cpp

diff --git a/src/dawn/native/Buffer.cpp b/src/dawn/native/Buffer.cpp
index 6749fa3..1114c9e 100644
--- a/src/dawn/native/Buffer.cpp
+++ b/src/dawn/native/Buffer.cpp
@@ -343,13 +343,16 @@
     }
 
     DeviceBase* device = GetDevice();
-    if (device->IsToggleEnabled(Toggle::LazyClearResourceOnFirstUse)) {
+    if (device->IsToggleEnabled(Toggle::LazyClearResourceOnFirstUse) &&
+        !device->IsToggleEnabled(Toggle::DisableLazyClearForMappedAtCreationBuffer)) {
         memset(ptr, uint8_t(0u), size);
-        SetIsDataInitialized();
         device->IncrementLazyClearCountForTesting();
     } else if (device->IsToggleEnabled(Toggle::NonzeroClearResourcesOnCreationForTesting)) {
         memset(ptr, uint8_t(1u), size);
     }
+    // Mark the buffer as initialized since we don't want to later clear it using the GPU since that
+    // would overwrite what the client wrote using the CPU.
+    SetIsDataInitialized();
 
     return {};
 }

src/dawn/native/Toggles.cpp

diff --git a/src/dawn/native/Toggles.cpp b/src/dawn/native/Toggles.cpp
index 020aa96..feab124 100644
--- a/src/dawn/native/Toggles.cpp
+++ b/src/dawn/native/Toggles.cpp
@@ -71,6 +71,10 @@
       "Clears resource to zero on first usage. This initializes the resource so that no dirty bits "
       "from recycled memory is present in the new resource.",
       "https://crbug.com/dawn/145", ToggleStage::Device}},
+    {Toggle::DisableLazyClearForMappedAtCreationBuffer,
+     {"disable_lazy_clear_for_mapped_at_creation_buffer",
+      "Disable clearing buffers to zero for buffers which are mapped at creation.",
+      "https://crbug.com/dawn/145", ToggleStage::Device}},
     {Toggle::TurnOffVsync,
      {"turn_off_vsync",
       "Turn off vsync when rendering. In order to do performance test or run perf tests, turn off "

src/dawn/native/Toggles.h

diff --git a/src/dawn/native/Toggles.h b/src/dawn/native/Toggles.h
index bd1ead7..3a05369 100644
--- a/src/dawn/native/Toggles.h
+++ b/src/dawn/native/Toggles.h
@@ -45,6 +45,7 @@
     NonzeroClearResourcesOnCreationForTesting,
     AlwaysResolveIntoZeroLevelAndLayer,
     LazyClearResourceOnFirstUse,
+    DisableLazyClearForMappedAtCreationBuffer,
     TurnOffVsync,
     UseTemporaryBufferInCompressedTextureToTextureCopy,
     UseD3D12ResourceHeapTier2,