Infer sampler precision from pixel config

src/gpu/vk/GrVkCaps.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrVkCaps.h"
 
 #include "GrVkUtil.h"
@@ skipping 135 matching lines @@
     // GrShaderCaps
 
     glslCaps->fShaderDerivativeSupport = true;
     glslCaps->fGeometryShaderSupport = SkToBool(featureFlags & kGeometryShader_GrVkFeatureFlag);
 #if 0
     // For now disabling dual source blending till we get it hooked up in the rest of system
     glslCaps->fDualSourceBlendingSupport = SkToBool(featureFlags & kDualSrcBlend_GrVkFeatureFlag);
 #endif
     glslCaps->fIntegerSupport = true;
 
+    // Assume the minimum precisions mandated by the GLSL spec for now.
+    glslCaps->fShaderPrecisionVaries = true;
+    for (int s = 0; s < kGrShaderTypeCount; ++s) {

[egdaniel, 2016/04/05 21:09:48]

in vulkan/SPIR-V,

highp in glsl maps to 32 bit float t IEEE 754 floating-point.
lowp/mediump maps to RelexedPrecision, see SPIR-V spec
(https://www.khronos.org/registry/spir-v/specs/1.0/SPIRV.pdf) for minimum
requirements for this precsion.

[Chris Dalton, 2016/04/05 21:54:49]

Done.

+        auto& lowp = glslCaps->fFloatPrecisions[s][kLow_GrSLPrecision];
+        lowp.fLogRangeLow = lowp.fLogRangeHigh = 1;
+        lowp.fBits = 8;
+
+        auto& mediump = glslCaps->fFloatPrecisions[s][kLow_GrSLPrecision];
+        mediump.fLogRangeLow = lowp.fLogRangeHigh = 14;
+        mediump.fBits = 10;
+
+        auto& highp = glslCaps->fFloatPrecisions[s][kLow_GrSLPrecision];
+        highp.fLogRangeLow = highp.fLogRangeHigh = 62;
+        highp.fBits = 16;
+    }
+    glslCaps->initEffectiveFloatPrecisionTable();
+
     glslCaps->fMaxVertexSamplers =
     glslCaps->fMaxGeometrySamplers =
     glslCaps->fMaxFragmentSamplers = SkTMin(properties.limits.maxPerStageDescriptorSampledImages,
                                             properties.limits.maxPerStageDescriptorSamplers);
     glslCaps->fMaxCombinedSamplers = SkTMin(properties.limits.maxDescriptorSetSampledImages,
                                             properties.limits.maxDescriptorSetSamplers);
 }
 
 static void format_supported_for_feature(const GrVkInterface* interface,
                                          VkPhysicalDevice physDev,
@@ skipping 107 matching lines @@
     static const StencilFormat
                   // internal Format             stencil bits      total bits        packed?
         gS8    = { VK_FORMAT_S8_UINT,            8,                 8,               false },
         gD24S8 = { VK_FORMAT_D24_UNORM_S8_UINT,  8,                32,               true };
 
     // I'm simply assuming that these two will be supported since they are used in example code.
     // TODO: Actaully figure this out
     SET_CONFIG_CAN_STENCIL(gS8);
     SET_CONFIG_CAN_STENCIL(gD24S8);
 }