Vulkan: No line raster emulation code if extension

A flag is added to the translator to disable generation of Bresenham line raster emulation code when the Bresenham line raster Vulkan extension is present. This is primarily for the sake of conversion of line raster emulation condition to specialization constant: - Avoid dead SPIR-V code in every shader - Avoid ANGLEUniforms being active in every shader stage even if it's not used anywhere but in line raster emulation. - Optimize SPIR-V transformations by both having fewer instructions to iterate through, and to avoid generating line raster patches. - Reduce the severity of anglebug.com/4251 where the location assignment of ANGLEPosition can incorrectly overlap a varying array or struct, by making only platforms without Bresenham extension afflicted by the bug. Bug: angleproject:3394 Change-Id: Ic0ae6ce0392b4eae0cc79cb94bbcd0805b276a31 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1986379Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>

Vulkan: No line raster emulation code if extension
0721cc8b · Shahbaz Youssefi · Commit Bot · f8ae5dc6 · 0721cc8b · 0721cc8b
Commit 0721cc8b authored Jan 03, 2020 by Shahbaz Youssefi Committed by Commit Bot Jan 06, 2020
Showing with 22 additions and 6 deletions

ShaderLang.h include/GLSLANG/ShaderLang.h +6 -1

TranslatorVulkan.cpp src/compiler/translator/TranslatorVulkan.cpp +11 -5

ShaderVk.cpp src/libANGLE/renderer/vulkan/ShaderVk.cpp +5 -0

No files found.
--- a/include/GLSLANG/ShaderLang.h
+++ b/include/GLSLANG/ShaderLang.h
@@ -26,7 +26,7 @@

 // Version number for shader translation API.
 // It is incremented every time the API changes.
-#define ANGLE_SH_VERSION 221
+#define ANGLE_SH_VERSION 222

 enum ShShaderSpec
 {
@@ -318,6 +318,11 @@ const ShCompileOptions SH_REMOVE_DYNAMIC_INDEXING_OF_SWIZZLED_VECTOR = UINT64_C(
 // on Windows 7 and earlier.
 const ShCompileOptions SH_DONT_TRANSLATE_UNIFORM_BLOCK_TO_STRUCTUREDBUFFER = UINT64_C(1) << 50;

+// This flag indicates whether Bresenham line raster emulation code should be generated.  This
+// emulation is necessary if the backend uses a differnet algorithm to draw lines.  Currently only
+// implemented for the Vulkan backend.
+const ShCompileOptions SH_ADD_BRESENHAM_LINE_RASTER_EMULATION = UINT64_C(1) << 51;
+
 // Defines alternate strategies for implementing array index clamping.
 enum ShArrayIndexClampingStrategy
 {

--- a/src/compiler/translator/TranslatorVulkan.cpp
+++ b/src/compiler/translator/TranslatorVulkan.cpp
@@ -870,10 +870,13 @@ bool TranslatorVulkan::translateImpl(TIntermBlock *root,
            }
        }

-        if (!AddBresenhamEmulationFS(this, sink, root, &getSymbolTable(), driverUniforms,
-                                     usesFragCoord))
+        if (compileOptions & SH_ADD_BRESENHAM_LINE_RASTER_EMULATION)
        {
-            return false;
+            if (!AddBresenhamEmulationFS(this, sink, root, &getSymbolTable(), driverUniforms,
+                                         usesFragCoord))
+            {
+                return false;
+            }
        }

        bool hasGLFragColor = false;
@@ -936,9 +939,12 @@ bool TranslatorVulkan::translateImpl(TIntermBlock *root,
    }
    else if (getShaderType() == GL_VERTEX_SHADER)
    {
-        if (!AddBresenhamEmulationVS(this, root, &getSymbolTable(), driverUniforms))
+        if (compileOptions & SH_ADD_BRESENHAM_LINE_RASTER_EMULATION)
        {
-            return false;
+            if (!AddBresenhamEmulationVS(this, root, &getSymbolTable(), driverUniforms))
+            {
+                return false;
+            }
        }

        // Add a macro to declare transform feedback buffers.

--- a/src/libANGLE/renderer/vulkan/ShaderVk.cpp
+++ b/src/libANGLE/renderer/vulkan/ShaderVk.cpp
@@ -40,6 +40,11 @@ std::shared_ptr<WaitableCompileEvent> ShaderVk::compile(const gl::Context *conte
        compileOptions |= SH_CLAMP_POINT_SIZE;
    }

+    if (contextVk->getFeatures().basicGLLineRasterization.enabled)
+    {
+        compileOptions |= SH_ADD_BRESENHAM_LINE_RASTER_EMULATION;
+    }
+
    if (contextVk->emulateSeamfulCubeMapSampling())
    {
        compileOptions |= SH_EMULATE_SEAMFUL_CUBE_MAP_SAMPLING;