Support constant folding of fragment processing built-ins

This change adds constant folding support for following derivative functions: - dFdx, dFdy and fwidth. As per spec, derivatives of constant arguments should be 0, so this change just sets result components to zero when the above operations are performed on constant argument. BUG=angleproject:913 TEST=dEQP Tests dEQP-GLES3.functional.shaders.constant_expressions.builtin_functions. fragment_processing.* (All 12 tests started passing with this change.) Change-Id: I67b7c5abd970b740e15e3bd1ee56721e81bbecc4 Reviewed-on: https://chromium-review.googlesource.com/283759Reviewed-by: Olli Etuaho <oetuaho@nvidia.com> Tested-by: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>

Support constant folding of fragment processing built-ins
0c5409f8 · Arun Patole · Jamie Madill · 551279e5 · 0c5409f8
Commit 0c5409f8 authored Jul 08, 2015 by Arun Patole Committed by Jamie Madill Jul 09, 2015
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IntermNode.cpp src/compiler/translator/IntermNode.cpp +12 -0

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--- a/src/compiler/translator/IntermNode.cpp
+++ b/src/compiler/translator/IntermNode.cpp
@@ -1827,6 +1827,18 @@ TConstantUnion *TIntermConstantUnion::foldUnaryWithSameReturnType(TOperator op, 
            infoSink.info.message(EPrefixInternalError, getLine(), "Unary operation not folded into constant");
            return nullptr;
+          case EOpDFdx:
+          case EOpDFdy:
+          case EOpFwidth:
+            if (getType().getBasicType() == EbtFloat)
+            {
+                // Derivatives of constant arguments should be 0.
+                resultArray[i].setFConst(0.0f);
+                break;
+            }
+            infoSink.info.message(EPrefixInternalError, getLine(), "Unary operation not folded into constant");
+            return nullptr;
          default:
            return nullptr;
        }