Reland "Remove GrProgramDesc::KeyHeader structure"

This is a reland of 4bcd58afbf

Original change's description:
> Remove GrProgramDesc::KeyHeader structure
>
> Instead, just fold all of this information into the key, like everything
> else. The only value that was accessed elsewhere is the initial key
> length. That doesn't need to be part of the key, so store it separately
> in the GrProgramDesc.
>
> Removing this special case logic is just the first step in revising how
> we assemble keys.
>
> Bug: skia:11372
> Change-Id: I52eb76812045e1906797cb37e809cfd0b3332ef0
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/376797
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>

Bug: skia:11372
Change-Id: I2cdb49aee3537e54dad9af1f9b47cf1aed1aca21
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/376849
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

src/gpu/GrProgramDesc.cpp

@@ -175,11 +175,7 @@ bool GrProgramDesc::Build(GrProgramDesc* desc,
     // bindings in use or other descriptor field settings) it should be set
     // to a canonical value to avoid duplicate programs with different keys.
 
-    static_assert(0 == kProcessorKeysOffset % sizeof(uint32_t));
-    // Make room for everything up to the effect keys.
     desc->key().reset();
-    desc->key().push_back_n(kProcessorKeysOffset);
-
     GrProcessorKeyBuilder b(&desc->key());
 
     const GrPrimitiveProcessor& primitiveProcessor = programInfo.primProc();
@@ -223,36 +219,29 @@ bool GrProgramDesc::Build(GrProgramDesc* desc,
         b.add32(renderTarget->getSamplePatternKey());
     }
 
-    // --------DO NOT MOVE HEADER ABOVE THIS LINE--------------------------------------------------
+    // Add "header" metadata
-    // Because header is a pointer into the dynamic array, we can't push any new data into the key
+    uint32_t header = 0;
-    // below here.
+    SkDEBUGCODE(uint32_t header_bits = 0);
-    KeyHeader* header = desc->atOffset<KeyHeader, kHeaderOffset>();
+    auto add_bits = [&](uint32_t nbits, uint32_t val) {
-
+        SkASSERT(val < (1 << nbits));
-    // make sure any padding in the header is zeroed.
+        SkASSERT((header_bits += nbits) <= 32);
-    memset(header, 0, kHeaderSize);
+        header = (header << nbits) | val;
-    header->fWriteSwizzle = pipeline.writeSwizzle().asKey();
+    };
-    header->fColorFragmentProcessorCnt = numColorFPs;
+    add_bits(16, pipeline.writeSwizzle().asKey());
-    header->fCoverageFragmentProcessorCnt = numCoverageFPs;
+    add_bits( 1, numColorFPs);
-    SkASSERT(header->fColorFragmentProcessorCnt == numColorFPs);
+    add_bits( 2, numCoverageFPs);
-    SkASSERT(header->fCoverageFragmentProcessorCnt == numCoverageFPs);
     // If we knew the shader won't depend on origin, we could skip this (and use the same program
     // for both origins). Instrumenting all fragment processors would be difficult and error prone.
-    header->fSurfaceOriginKey =
+    add_bits( 2, GrGLSLFragmentShaderBuilder::KeyForSurfaceOrigin(programInfo.origin()));
-                    GrGLSLFragmentShaderBuilder::KeyForSurfaceOrigin(programInfo.origin());
+    add_bits( 1, static_cast<uint32_t>(programInfo.requestedFeatures()));
-    header->fProcessorFeatures = (uint8_t)programInfo.requestedFeatures();
+    add_bits( 1, pipeline.snapVerticesToPixelCenters());
-    // Ensure enough bits.
-    SkASSERT(header->fProcessorFeatures == (int) programInfo.requestedFeatures());
-    header->fSnapVerticesToPixelCenters = pipeline.snapVerticesToPixelCenters();
     // The base descriptor only stores whether or not the primitiveType is kPoints. Backend-
     // specific versions (e.g., Vulkan) require more detail
-    header->fHasPointSize = (programInfo.primitiveType() == GrPrimitiveType::kPoints);
+    add_bits( 1, (programInfo.primitiveType() == GrPrimitiveType::kPoints));
 
-    header->fInitialKeyLength = desc->keyLength();
+    b.add32(header);
-    // Fail if the initial key length won't fit in 27 bits.
+
-    if (header->fInitialKeyLength != desc->keyLength()) {
+    desc->fInitialKeyLength = desc->keyLength();
-        desc->key().reset();
-        return false;
-    }
 
     return true;
 }

src/gpu/GrProgramDesc.h

@@ -22,7 +22,7 @@ class GrShaderCaps;
  */
 class GrProgramDesc {
 public:
-    GrProgramDesc(const GrProgramDesc& other) : fKey(other.fKey) {}   // for SkLRUCache
+    GrProgramDesc(const GrProgramDesc& other) = default;
 
     bool isValid() const { return !fKey.empty(); }
 
@@ -41,6 +41,7 @@ public:
         uint32_t keyLength = other.keyLength();
         fKey.reset(SkToInt(keyLength));
         memcpy(fKey.begin(), other.fKey.begin(), keyLength);
+        fInitialKeyLength = other.fInitialKeyLength;
         return *this;
     }
 
@@ -65,7 +66,7 @@ public:
         return !(*this == other);
     }
 
-    uint32_t initialKeyLength() const { return this->header().fInitialKeyLength; }
+    uint32_t initialKeyLength() const { return fInitialKeyLength; }
 
 protected:
     friend class GrDawnCaps;
@@ -100,48 +101,11 @@ protected:
         return true;
     }
 
-    // TODO: this should be removed and converted to just data added to the key
-    struct KeyHeader {
-        // Set to uniquely identify any swizzling of the shader's output color(s).
-        uint16_t fWriteSwizzle;
-        uint8_t fColorFragmentProcessorCnt; // Can be packed into 4 bits if required.
-        uint8_t fCoverageFragmentProcessorCnt;
-        // Set to uniquely identify the rt's origin, or 0 if the shader does not require this info.
-        uint32_t fSurfaceOriginKey : 2;
-        uint32_t fProcessorFeatures : 1;
-        uint32_t fSnapVerticesToPixelCenters : 1;
-        uint32_t fHasPointSize : 1;
-        // This is the key size (in bytes) after core key construction. It doesn't include any
-        // portions added by the platform-specific backends.
-        uint32_t fInitialKeyLength : 27;
-    };
-    static_assert(sizeof(KeyHeader) == 8);
-
-    const KeyHeader& header() const { return *this->atOffset<KeyHeader, kHeaderOffset>(); }
-
-    template<typename T, size_t OFFSET> T* atOffset() {
-        return reinterpret_cast<T*>(reinterpret_cast<intptr_t>(fKey.begin()) + OFFSET);
-    }
-
-    template<typename T, size_t OFFSET> const T* atOffset() const {
-        return reinterpret_cast<const T*>(reinterpret_cast<intptr_t>(fKey.begin()) + OFFSET);
-    }
-
-    // The key, stored in fKey, is composed of two parts:
-    // 1. Header struct defined above.
-    // 2. A Backend specific payload which includes the per-processor keys.
-    enum KeyOffsets {
-        kHeaderOffset = 0,
-        kHeaderSize = SkAlign4(sizeof(KeyHeader)),
-        // This is the offset into the backend-specific part of the key, which includes
-        // per-processor keys.
-        kProcessorKeysOffset = kHeaderOffset + kHeaderSize,
-    };
-
     enum {
+        kHeaderSize            = 4,    // "header" in ::Build
         kMaxPreallocProcessors = 8,
         kIntsPerProcessor      = 4,    // This is an overestimate of the average effect key size.
-        kPreAllocSize = kHeaderOffset + kHeaderSize +
+        kPreAllocSize = kHeaderSize +
                         kMaxPreallocProcessors * sizeof(uint32_t) * kIntsPerProcessor,
     };
 
@@ -149,6 +113,7 @@ protected:
 
 private:
     SkSTArray<kPreAllocSize, uint8_t, true> fKey;
+    uint32_t fInitialKeyLength = 0;
 };
 
 #endif