Add remove_pow_with_constant_exponent workaround

Bug: chromium: 477306, 829614
Change-Id: If88c57b15a4cfd6f362a2f5171f8e9c0775cb9d4
Reviewed-on: https://skia-review.googlesource.com/148480
Commit-Queue: Adrienne Walker <enne@chromium.org>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>

include/gpu/GrDriverBugWorkaroundsAutogen.h

@@ -28,6 +28,8 @@
          max_texture_size_limit_4096)                   \
   GPU_OP(PACK_PARAMETERS_WORKAROUND_WITH_PACK_BUFFER,   \
          pack_parameters_workaround_with_pack_buffer)   \
+  GPU_OP(REMOVE_POW_WITH_CONSTANT_EXPONENT,             \
+         remove_pow_with_constant_exponent)             \
   GPU_OP(RESTORE_SCISSOR_ON_FBO_CHANGE,                 \
          restore_scissor_on_fbo_change)                 \
   GPU_OP(REWRITE_DO_WHILE_LOOPS,                        \

src/gpu/GrShaderCaps.cpp

@@ -42,6 +42,7 @@ GrShaderCaps::GrShaderCaps(const GrContextOptions& options) {
     fUnfoldShortCircuitAsTernary = false;
     fEmulateAbsIntFunction = false;
     fRewriteDoWhileLoops = false;
+    fRemovePowWithConstantExponent = false;
     fFlatInterpolationSupport = false;
     fPreferFlatInterpolation = false;
     fNoPerspectiveInterpolationSupport = false;
@@ -112,6 +113,7 @@ void GrShaderCaps::dumpJSON(SkJSONWriter* writer) const {
     writer->appendBool("Unfold short circuit as ternary", fUnfoldShortCircuitAsTernary);
     writer->appendBool("Emulate abs(int) function", fEmulateAbsIntFunction);
     writer->appendBool("Rewrite do while loops", fRewriteDoWhileLoops);
+    writer->appendBool("Rewrite pow with constant exponent", fRemovePowWithConstantExponent);
     writer->appendBool("Flat interpolation support", fFlatInterpolationSupport);
     writer->appendBool("Prefer flat interpolation", fPreferFlatInterpolation);
     writer->appendBool("No perspective interpolation support", fNoPerspectiveInterpolationSupport);
@@ -148,6 +150,7 @@ void GrShaderCaps::applyOptionsOverrides(const GrContextOptions& options) {
         SkASSERT(!fUnfoldShortCircuitAsTernary);
         SkASSERT(!fEmulateAbsIntFunction);
         SkASSERT(!fRewriteDoWhileLoops);
+        SkASSERT(!fRemovePowWithConstantExponent);
     }
 #if GR_TEST_UTILS
     fDualSourceBlendingSupport = fDualSourceBlendingSupport && !options.fSuppressDualSourceBlending;

src/gpu/GrShaderCaps.h

@@ -135,6 +135,8 @@ public:
 
     bool rewriteDoWhileLoops() const { return fRewriteDoWhileLoops; }
 
+    bool removePowWithConstantExponent() const { return fRemovePowWithConstantExponent; }
+
     bool requiresLocalOutputColorForFBFetch() const { return fRequiresLocalOutputColorForFBFetch; }
 
     bool mustObfuscateUniformColor() const { return fMustObfuscateUniformColor; }
@@ -274,6 +276,7 @@ private:
     bool fUnfoldShortCircuitAsTernary                 : 1;
     bool fEmulateAbsIntFunction                       : 1;
     bool fRewriteDoWhileLoops                         : 1;
+    bool fRemovePowWithConstantExponent               : 1;
 
     const char* fVersionDeclString;
 

src/gpu/gl/GrGLCaps.cpp

@@ -2585,6 +2585,10 @@ void GrGLCaps::applyDriverCorrectnessWorkarounds(const GrGLContextInfo& ctxInfo,
         shaderCaps->fRewriteDoWhileLoops = true;
     }
 
+    if (fDriverBugWorkarounds.remove_pow_with_constant_exponent) {
+        shaderCaps->fRemovePowWithConstantExponent = true;
+    }
+
     // Disabling advanced blend on various platforms with major known issues. We also block Chrome
     // for now until its own blacklists can be updated.
     if (kAdreno430_GrGLRenderer == ctxInfo.renderer() ||

src/gpu/gpu_workaround_list.txt

@@ -9,6 +9,7 @@ max_fragment_uniform_vectors_32
 max_msaa_sample_count_4
 max_texture_size_limit_4096
 pack_parameters_workaround_with_pack_buffer
+remove_pow_with_constant_exponent
 restore_scissor_on_fbo_change
 rewrite_do_while_loops
 unbind_attachments_on_bound_render_fbo_delete

src/sksl/SkSLGLSLCodeGenerator.cpp

@@ -470,6 +470,7 @@ void GLSLCodeGenerator::writeFunctionCall(const FunctionCall& c) {
         (*fFunctionClasses)["inverse"]     = FunctionClass::kInverse;
         (*fFunctionClasses)["inverseSqrt"] = FunctionClass::kInverseSqrt;
         (*fFunctionClasses)["min"]         = FunctionClass::kMin;
+        (*fFunctionClasses)["pow"]         = FunctionClass::kPow;
         (*fFunctionClasses)["saturate"]    = FunctionClass::kSaturate;
         (*fFunctionClasses)["texture"]     = FunctionClass::kTexture;
         (*fFunctionClasses)["transpose"]   = FunctionClass::kTranspose;
@@ -573,6 +574,21 @@ void GLSLCodeGenerator::writeFunctionCall(const FunctionCall& c) {
                     }
                 }
                 break;
+            case FunctionClass::kPow:
+                if (!fProgram.fSettings.fCaps->removePowWithConstantExponent()) {
+                    break;
+                }
+                // pow(x, y) on some NVIDIA drivers causes crashes if y is a
+                // constant.  It's hard to tell what constitutes "constant" here
+                // so just replace in all cases.
+
+                // Change pow(x, y) into exp2(y * log2(x))
+                this->write("exp2(");
+                this->writeExpression(*c.fArguments[1], kMultiplicative_Precedence);
+                this->write(" * log2(");
+                this->writeExpression(*c.fArguments[0], kSequence_Precedence);
+                this->write("))");
+                return;
             case FunctionClass::kSaturate:
                 SkASSERT(c.fArguments.size() == 1);
                 this->write("clamp(");

src/sksl/SkSLGLSLCodeGenerator.h

@@ -231,6 +231,7 @@ protected:
         kInverse,
         kInverseSqrt,
         kMin,
+        kPow,
         kSaturate,
         kTexture,
         kTranspose

src/sksl/SkSLUtil.h

@@ -193,6 +193,10 @@ public:
         return false;
     }
 
+    bool removePowWithConstantExponent() const {
+        return false;
+    }
+
     const char* fbFetchColorName() const {
         return nullptr;
     }
@@ -364,6 +368,13 @@ public:
         result->fRewriteDoWhileLoops = true;
         return result;
     }
+
+    static sk_sp<GrShaderCaps> RemovePowWithConstantExponent() {
+        sk_sp<GrShaderCaps> result = sk_make_sp<GrShaderCaps>(GrContextOptions());
+        result->fVersionDeclString = "#version 400";
+        result->fRemovePowWithConstantExponent = true;
+        return result;
+    }
 };
 #endif
 

tests/SkSLGLSLTest.cpp

@@ -2094,3 +2094,24 @@ DEF_TEST(SkSLWorkaroundRewriteDoWhileLoops, r) {
          SkSL::Program::kFragment_Kind
          );
 }
+
+DEF_TEST(SkSLWorkaroundRemovePowWithConstantExponent, r) {
+    test(r,
+         "uniform float x;"
+         "uniform float y;"
+         "void main() {"
+         "    float z = pow(x + 1.0, y + 2.0);"
+         "    sk_FragColor = float4(z);"
+         "}",
+         *SkSL::ShaderCapsFactory::RemovePowWithConstantExponent(),
+         "#version 400\n"
+         "out vec4 sk_FragColor;\n"
+         "uniform float x;\n"
+         "uniform float y;\n"
+         "void main() {\n"
+         "    float z = exp2((y + 2.0) * log2(x + 1.0));\n"
+         "    sk_FragColor = vec4(z);\n"
+         "}\n",
+         SkSL::Program::kFragment_Kind
+         );
+}