Consolidate sampler->index/key conversion

Share code between GL and other backends.

Prepare for separate GrSamplerState field to control mip mapping.

Bug: skia:10344

Change-Id: I16adae3512e11971f98c63ae08fb8cde31332520
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/302910
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>

src/gpu/GrSamplerState.h

@@ -9,6 +9,7 @@
 #define GrSamplerState_DEFINED
 
 #include "include/gpu/GrTypes.h"
+#include <limits>
 
 /**
  * Represents the filtering and tile modes used to access a texture.
@@ -61,25 +62,28 @@ public:
 
     constexpr bool operator!=(const GrSamplerState& that) const { return !(*this == that); }
 
-    constexpr static uint8_t GenerateKey(GrSamplerState samplerState) {
-        const int kTileModeXShift = 2;
-        const int kTileModeYShift = 4;
-
-        SkASSERT(static_cast<int>(samplerState.filter()) <= 3);
-        uint8_t key = static_cast<uint8_t>(samplerState.filter());
-
-        SkASSERT(static_cast<int>(samplerState.wrapModeX()) <= 3);
-        key |= (static_cast<uint8_t>(samplerState.wrapModeX()) << kTileModeXShift);
-
-        SkASSERT(static_cast<int>(samplerState.wrapModeY()) <= 3);
-        key |= (static_cast<uint8_t>(samplerState.wrapModeY()) << kTileModeYShift);
-
-        return key;
+    /**
+     * Turn the sampler state into an integer from a tightly packed range for use as an index
+     * (or key)
+     */
+    constexpr uint8_t asIndex() const {
+        constexpr int kNumWraps   = static_cast<int>(WrapMode::kLast) + 1;
+        int result = static_cast<int>(fWrapModes[0])*1
+                   + static_cast<int>(fWrapModes[1])*kNumWraps
+                   + static_cast<int>(fFilter)      *kNumWraps*kNumWraps;
+        SkASSERT(result <= kNumUniqueSamplers);
+        return static_cast<uint8_t>(result);
     }
 
+    static constexpr int kNumUniqueSamplers = (static_cast<int>(WrapMode::kLast) + 1)
+                                            * (static_cast<int>(WrapMode::kLast) + 1)
+                                            * (static_cast<int>(Filter::kLast  ) + 1);
 private:
     WrapMode fWrapModes[2] = {WrapMode::kClamp, WrapMode::kClamp};
     Filter fFilter = GrSamplerState::Filter::kNearest;
 };
 
+static_assert(GrSamplerState::kNumUniqueSamplers <=
+              std::numeric_limits<decltype(GrSamplerState{}.asIndex())>::max());
+
 #endif

src/gpu/d3d/GrD3DResourceProvider.cpp

@@ -126,7 +126,7 @@ static D3D12_TEXTURE_ADDRESS_MODE wrap_mode_to_d3d_address_mode(GrSamplerState::
 
 D3D12_CPU_DESCRIPTOR_HANDLE GrD3DResourceProvider::findOrCreateCompatibleSampler(
         const GrSamplerState& params) {
-    uint32_t key = GrSamplerState::GenerateKey(params);
+    uint32_t key = params.asIndex();
     D3D12_CPU_DESCRIPTOR_HANDLE* samplerPtr = fSamplers.find(key);
     if (samplerPtr) {
         return *samplerPtr;

src/gpu/d3d/GrD3DTexture.h

@@ -81,9 +81,7 @@ private:
     void removeFinishIdleProcs();
 
     struct SamplerHash {
-        uint32_t operator()(GrSamplerState state) const {
-            return GrSamplerState::GenerateKey(state);
-        }
+        uint32_t operator()(GrSamplerState state) const { return state.asIndex(); }
     };
 
     GrD3DDescriptorHeap::CPUHandle fShaderResourceView;

src/gpu/gl/GrGLGpu.cpp

@@ -232,7 +232,7 @@ public:
     }
 
     void bindSampler(int unitIdx, GrSamplerState state) {
-        int index = StateToIndex(state);
+        int index = state.asIndex();
         if (!fSamplers[index]) {
             GrGLuint s;
             GR_GL_CALL(fGpu->glInterface(), GenSamplers(1, &s));
@@ -280,20 +280,8 @@ public:
     }
 
 private:
-    static int StateToIndex(GrSamplerState state) {
-        int filter = static_cast<int>(state.filter());
-        SkASSERT(filter >= 0 && filter < 3);
-        int wrapX = static_cast<int>(state.wrapModeX());
-        SkASSERT(wrapX >= 0 && wrapX < 4);
-        int wrapY = static_cast<int>(state.wrapModeY());
-        SkASSERT(wrapY >= 0 && wrapY < 4);
-        int idx = 16 * filter + 4 * wrapX + wrapY;
-        SkASSERT(idx < kNumSamplers);
-        return idx;
-    }
-
+    static constexpr int kNumSamplers = GrSamplerState::kNumUniqueSamplers;
     GrGLGpu* fGpu;
-    static constexpr int kNumSamplers = 48;
     std::unique_ptr<GrGLuint[]> fHWBoundSamplers;
     GrGLuint fSamplers[kNumSamplers];
     int fNumTextureUnits;

src/gpu/mtl/GrMtlSampler.mm

@@ -74,5 +74,5 @@ GrMtlSampler* GrMtlSampler::Create(const GrMtlGpu* gpu, GrSamplerState samplerSt
 }
 
 GrMtlSampler::Key GrMtlSampler::GenerateKey(GrSamplerState samplerState) {
-    return GrSamplerState::GenerateKey(samplerState);
+    return samplerState.asIndex();
 }

src/gpu/vk/GrVkSampler.cpp

@@ -122,6 +122,5 @@ void GrVkSampler::freeGPUData() const {
 
 GrVkSampler::Key GrVkSampler::GenerateKey(GrSamplerState samplerState,
                                           const GrVkYcbcrConversionInfo& ycbcrInfo) {
-    return { GrSamplerState::GenerateKey(samplerState),
-             GrVkSamplerYcbcrConversion::GenerateKey(ycbcrInfo) };
+    return {samplerState.asIndex(), GrVkSamplerYcbcrConversion::GenerateKey(ycbcrInfo)};
 }

src/gpu/vk/GrVkTexture.h

@@ -97,9 +97,7 @@ private:
     const GrVkImageView* fTextureView;
 
     struct SamplerHash {
-        uint32_t operator()(GrSamplerState state) const {
-            return GrSamplerState::GenerateKey(state);
-        }
+        uint32_t operator()(GrSamplerState state) const { return state.asIndex(); }
     };
     struct DescriptorCacheEntry;
     SkLRUCache<const GrSamplerState, std::unique_ptr<DescriptorCacheEntry>, SamplerHash>