Add rewrite_do_while_loops workaround

Bug: chromium: 644669, 829614
Change-Id: Ic6a4cbd9f7c73b9b9a78608f1b4ac4ce4c4f2cb9
Reviewed-on: https://skia-review.googlesource.com/148439
Commit-Queue: Adrienne Walker <enne@chromium.org>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>

include/gpu/GrDriverBugWorkaroundsAutogen.h

@@ -30,6 +30,8 @@
          pack_parameters_workaround_with_pack_buffer)   \
   GPU_OP(RESTORE_SCISSOR_ON_FBO_CHANGE,                 \
          restore_scissor_on_fbo_change)                 \
+  GPU_OP(REWRITE_DO_WHILE_LOOPS,                        \
+         rewrite_do_while_loops)                        \
   GPU_OP(UNBIND_ATTACHMENTS_ON_BOUND_RENDER_FBO_DELETE, \
          unbind_attachments_on_bound_render_fbo_delete) \
   GPU_OP(UNFOLD_SHORT_CIRCUIT_AS_TERNARY_OPERATION,     \

src/gpu/GrShaderCaps.cpp

@@ -41,6 +41,7 @@ GrShaderCaps::GrShaderCaps(const GrContextOptions& options) {
     fAddAndTrueToLoopCondition = false;
     fUnfoldShortCircuitAsTernary = false;
     fEmulateAbsIntFunction = false;
+    fRewriteDoWhileLoops = false;
     fFlatInterpolationSupport = false;
     fPreferFlatInterpolation = false;
     fNoPerspectiveInterpolationSupport = false;
@@ -110,6 +111,7 @@ void GrShaderCaps::dumpJSON(SkJSONWriter* writer) const {
     writer->appendBool("Add and true to loops workaround", fAddAndTrueToLoopCondition);
     writer->appendBool("Unfold short circuit as ternary", fUnfoldShortCircuitAsTernary);
     writer->appendBool("Emulate abs(int) function", fEmulateAbsIntFunction);
+    writer->appendBool("Rewrite do while loops", fRewriteDoWhileLoops);
     writer->appendBool("Flat interpolation support", fFlatInterpolationSupport);
     writer->appendBool("Prefer flat interpolation", fPreferFlatInterpolation);
     writer->appendBool("No perspective interpolation support", fNoPerspectiveInterpolationSupport);
@@ -145,6 +147,7 @@ void GrShaderCaps::applyOptionsOverrides(const GrContextOptions& options) {
         SkASSERT(!fAddAndTrueToLoopCondition);
         SkASSERT(!fUnfoldShortCircuitAsTernary);
         SkASSERT(!fEmulateAbsIntFunction);
+        SkASSERT(!fRewriteDoWhileLoops);
     }
 #if GR_TEST_UTILS
     fDualSourceBlendingSupport = fDualSourceBlendingSupport && !options.fSuppressDualSourceBlending;

src/gpu/GrShaderCaps.h

@@ -133,6 +133,8 @@ public:
 
     bool emulateAbsIntFunction() const { return fEmulateAbsIntFunction; }
 
+    bool rewriteDoWhileLoops() const { return fRewriteDoWhileLoops; }
+
     bool requiresLocalOutputColorForFBFetch() const { return fRequiresLocalOutputColorForFBFetch; }
 
     bool mustObfuscateUniformColor() const { return fMustObfuscateUniformColor; }
@@ -271,6 +273,7 @@ private:
     bool fAddAndTrueToLoopCondition                   : 1;
     bool fUnfoldShortCircuitAsTernary                 : 1;
     bool fEmulateAbsIntFunction                       : 1;
+    bool fRewriteDoWhileLoops                         : 1;
 
     const char* fVersionDeclString;
 

src/gpu/gl/GrGLCaps.cpp

@@ -2581,6 +2581,10 @@ void GrGLCaps::applyDriverCorrectnessWorkarounds(const GrGLContextInfo& ctxInfo,
         shaderCaps->fEmulateAbsIntFunction = true;
     }
 
+    if (fDriverBugWorkarounds.rewrite_do_while_loops) {
+        shaderCaps->fRewriteDoWhileLoops = 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

@@ -10,5 +10,6 @@ max_msaa_sample_count_4
 max_texture_size_limit_4096
 pack_parameters_workaround_with_pack_buffer
 restore_scissor_on_fbo_change
+rewrite_do_while_loops
 unbind_attachments_on_bound_render_fbo_delete
 unfold_short_circuit_as_ternary_operation

src/sksl/SkSLGLSLCodeGenerator.cpp

@@ -1334,11 +1334,56 @@ void GLSLCodeGenerator::writeWhileStatement(const WhileStatement& w) {
 }
 
 void GLSLCodeGenerator::writeDoStatement(const DoStatement& d) {
-    this->write("do ");
+    if (!fProgram.fSettings.fCaps->rewriteDoWhileLoops()) {
+        this->write("do ");
+        this->writeStatement(*d.fStatement);
+        this->write(" while (");
+        this->writeExpression(*d.fTest, kTopLevel_Precedence);
+        this->write(");");
+        return;
+    }
+
+    // Otherwise, do the do while loop workaround, to rewrite loops of the form:
+    //     do {
+    //         CODE;
+    //     } while (CONDITION)
+    //
+    // to loops of the form
+    //     bool temp = false;
+    //     while (true) {
+    //         if (temp) {
+    //             if (!CONDITION) {
+    //                 break;
+    //             }
+    //         }
+    //         temp = true;
+    //         CODE;
+    //     }
+    String tmpVar = "_tmpLoopSeenOnce" + to_string(fVarCount++);
+    this->write("bool ");
+    this->write(tmpVar);
+    this->writeLine(" = false;");
+    this->writeLine("while (true) {");
+    fIndentation++;
+    this->write("if (");
+    this->write(tmpVar);
+    this->writeLine(") {");
+    fIndentation++;
+    this->write("if (!");
+    this->writeExpression(*d.fTest, kPrefix_Precedence);
+    this->writeLine(") {");
+    fIndentation++;
+    this->writeLine("break;");
+    fIndentation--;
+    this->writeLine("}");
+    fIndentation--;
+    this->writeLine("}");
+    this->write(tmpVar);
+    this->writeLine(" = true;");
     this->writeStatement(*d.fStatement);
-    this->write(" while (");
-    this->writeExpression(*d.fTest, kTopLevel_Precedence);
-    this->write(");");
+    this->writeLine();
+    fIndentation--;
+    this->write("}");
 }
 
 void GLSLCodeGenerator::writeSwitchStatement(const SwitchStatement& s) {

src/sksl/SkSLUtil.h

@@ -189,6 +189,10 @@ public:
         return false;
     }
 
+    bool rewriteDoWhileLoops() const {
+        return false;
+    }
+
     const char* fbFetchColorName() const {
         return nullptr;
     }
@@ -353,6 +357,13 @@ public:
         result->fEmulateAbsIntFunction = true;
         return result;
     }
+
+    static sk_sp<GrShaderCaps> RewriteDoWhileLoops() {
+        sk_sp<GrShaderCaps> result = sk_make_sp<GrShaderCaps>(GrContextOptions());
+        result->fVersionDeclString = "#version 400";
+        result->fRewriteDoWhileLoops = true;
+        return result;
+    }
 };
 #endif
 

tests/SkSLGLSLTest.cpp

@@ -2047,3 +2047,50 @@ DEF_TEST(SkSLWorkaroundEmulateAbsIntFunction, r) {
          SkSL::Program::kFragment_Kind
          );
 }
+
+DEF_TEST(SkSLWorkaroundRewriteDoWhileLoops, r) {
+    test(r,
+         "void main() {"
+         "    int i = 0;"
+         "    do {"
+         "      ++i;"
+         "      do {"
+         "        i++;"
+         "      } while (true);"
+         "    } while (i < 10);"
+         "    sk_FragColor = float4(i);"
+         "}",
+         *SkSL::ShaderCapsFactory::RewriteDoWhileLoops(),
+         "#version 400\n"
+         "out vec4 sk_FragColor;\n"
+         "void main() {\n"
+         "    int i = 0;\n"
+         "    bool _tmpLoopSeenOnce0 = false;\n"
+         "    while (true) {\n"
+         "        if (_tmpLoopSeenOnce0) {\n"
+         "            if (!(i < 10)) {\n"
+         "                break;\n"
+         "            }\n"
+         "        }\n"
+         "        _tmpLoopSeenOnce0 = true;\n"
+         "        {\n"
+         "            ++i;\n"
+         "            bool _tmpLoopSeenOnce1 = false;\n"
+         "            while (true) {\n"
+         "                if (_tmpLoopSeenOnce1) {\n"
+         "                    if (!true) {\n"
+         "                        break;\n"
+         "                    }\n"
+         "                }\n"
+         "                _tmpLoopSeenOnce1 = true;\n"
+         "                {\n"
+         "                    i++;\n"
+         "                }\n"
+         "            }\n"
+         "        }\n"
+         "    }\n"
+         "    sk_FragColor = vec4(float(i));\n"
+         "}\n",
+         SkSL::Program::kFragment_Kind
+         );
+}