From c4f083cfba41244c33eaff5c074dcf5ea07e04c8 Mon Sep 17 00:00:00 2001
From: Mathias Agopian <mathias@google.com>
Date: Fri, 5 Sep 2025 13:31:03 -0700
Subject: [PATCH] matc and MaterialBuilder workaround options NONE by default

The workaround option is now set to none by default. Use

```
matc -Wall
```

if you want to restore the previous behavior.

Current material workarounds:
- remove MergeReturnPass (except on Metal)
- remove SimplificationPass (except on Metal)

There are reason to believe these workarounds are no longer needed,
due to changes in spirv-opt.

It's possible that older devices might still need them.

These workaround affect *all* devices, this is why it is important
to disable them if not needed.
---
 NEW_RELEASE_NOTES.md                            |  1 +
 libs/filamat/include/filamat/MaterialBuilder.h  |  2 +-
 libs/filamat/src/GLSLPostProcessor.cpp          | 17 ++++++++++++++++-
 .../include/filament-matp/Config.h              |  2 +-
 tools/matc/src/matc/CommandlineConfig.cpp       |  2 +-
 5 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/NEW_RELEASE_NOTES.md b/NEW_RELEASE_NOTES.md
index 68a3814f05..50e3b97e93 100644
--- a/NEW_RELEASE_NOTES.md
+++ b/NEW_RELEASE_NOTES.md
@@ -12,3 +12,4 @@ appropriate header in [RELEASE_NOTES.md](./RELEASE_NOTES.md).
   available on Metal). Non-Metal backends can use the callback to be notified when Filament has
   finished processing a frame on the CPU.
 - materials: added `getEyeFromViewMatrix()` for vertex shader [⚠️ **Recompile Materials**]
+- matc: make `--workarounds=none` the default [**Recompile Materials to take effect**]
diff --git a/libs/filamat/include/filamat/MaterialBuilder.h b/libs/filamat/include/filamat/MaterialBuilder.h
index 7b0ca3c111..004b16dca0 100644
--- a/libs/filamat/include/filamat/MaterialBuilder.h
+++ b/libs/filamat/include/filamat/MaterialBuilder.h
@@ -146,7 +146,7 @@ protected:
     Platform mPlatform = Platform::DESKTOP;
     TargetApi mTargetApi = (TargetApi) 0;
     Optimization mOptimization = Optimization::PERFORMANCE;
-    Workarounds mWorkarounds = Workarounds::ALL;
+    Workarounds mWorkarounds = Workarounds::NONE;
     bool mPrintShaders = false;
     bool mSaveRawVariants = false;
     bool mGenerateDebugInfo = false;
diff --git a/libs/filamat/src/GLSLPostProcessor.cpp b/libs/filamat/src/GLSLPostProcessor.cpp
index f8745a464d..06ea410673 100644
--- a/libs/filamat/src/GLSLPostProcessor.cpp
+++ b/libs/filamat/src/GLSLPostProcessor.cpp
@@ -1051,7 +1051,6 @@ void GLSLPostProcessor::fixupClipDistance(
 void GLSLPostProcessor::registerPerformancePasses(Optimizer& optimizer, Config const& config) {
     auto RegisterPass = [&](Optimizer::PassToken&& pass,
             MaterialBuilder::TargetApi apiFilter = MaterialBuilder::TargetApi::ALL) {
-
         // Workaround management is currently very simple, only two values are possible
         // ALL and NONE. If the value is anything but NONE, we apply all workarounds.
         if (config.workarounds != MaterialBuilderBase::Workarounds::NONE) {
@@ -1060,6 +1059,22 @@ void GLSLPostProcessor::registerPerformancePasses(Optimizer& optimizer, Config c
             }
         }
 
+        // FIXME: Workaround within a workaround!!! We IGNORE config.workarounds for WEBGPU
+        //        because Tint doesn't even compile with MergeReturn/Simplification pass
+        //        active:
+        //            Tint Reader Error: warning: code is unreachable
+        //            error: no matching overload for 'operator << (i32, i32)'
+        //            2 candidate operators:
+        //             • 'operator << (T  ✓ , u32  ✗ ) -> T' where:
+        //                  ✓  'T' is 'abstract-int', 'i32' or 'u32'
+        //             • 'operator << (vecN<T>  ✗ , vecN<u32>  ✗ ) -> vecN<T>' where:
+        //                  ✗  'T' is 'abstract-int', 'i32' or 'u32'
+        if (any(config.targetApi & MaterialBuilder::TargetApi::WEBGPU)) {
+            if (!(config.targetApi & apiFilter)) {
+                return;
+            }
+        }
+
         optimizer.RegisterPass(std::move(pass));
     };
 
diff --git a/libs/filament-matp/include/filament-matp/Config.h b/libs/filament-matp/include/filament-matp/Config.h
index 7a8f1941e5..b40e113d61 100644
--- a/libs/filament-matp/include/filament-matp/Config.h
+++ b/libs/filament-matp/include/filament-matp/Config.h
@@ -171,7 +171,7 @@ protected:
     StringReplacementMap mTemplateMap;
     StringReplacementMap mMaterialParameters;
     filament::UserVariantFilterMask mVariantFilter = 0;
-    Workarounds mWorkarounds = Workarounds::ALL;
+    Workarounds mWorkarounds = Workarounds::NONE;
     bool mIncludeEssl1 = true;
 };
 
diff --git a/tools/matc/src/matc/CommandlineConfig.cpp b/tools/matc/src/matc/CommandlineConfig.cpp
index 6bc3d30465..b77f4e4d73 100644
--- a/tools/matc/src/matc/CommandlineConfig.cpp
+++ b/tools/matc/src/matc/CommandlineConfig.cpp
@@ -146,7 +146,7 @@ static void usage(char* name) {
             "           ssr (screen-space reflections), stereo\n"
             "       This variant filter is merged with the filter from the material, if any\n\n"
             "   --workarounds, -W\n"
-            "       Workarounds to apply: all or none. (default is all).\n\n"
+            "       Workarounds to apply: all or none. (default is none).\n\n"
             "   --version, -v\n"
             "       Print the material version number\n\n"
             "Internal use and debugging only:\n"