Support constant folding of exponential built-ins

This change adds constant folding support for unary exponential built-ins - exp, log, exp2, log2, sqrt and inversesqrt. BUG=angleproject:913 TEST= dEQP tests dEQP-GLES3.functional.shaders.constant_expressions.builtin_functions.exponential* (48 out of 56 tests started passing with this change) Change-Id: I22af56876d1b7ce305697bf9bf43ad9ec5d8a3a5 Reviewed-on: https://chromium-review.googlesource.com/263708Reviewed-by: Olli Etuaho <oetuaho@nvidia.com> Tested-by: Olli Etuaho <oetuaho@nvidia.com>

Support constant folding of exponential built-ins
1c89caef · Arun Patole · Olli Etuaho · af930db1 · 1c89caef
Commit 1c89caef authored Apr 06, 2015 by Arun Patole Committed by Olli Etuaho Apr 10, 2015
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IntermNode.cpp src/compiler/translator/IntermNode.cpp +46 -0

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--- a/src/compiler/translator/IntermNode.cpp
+++ b/src/compiler/translator/IntermNode.cpp
@@ -1284,6 +1284,52 @@ TIntermTyped *TIntermConstantUnion::fold(
                    return nullptr;
                break;
+              case EOpExp:
+                if (!foldFloatTypeUnary(unionArray[i], static_cast<FloatTypeUnaryFunc>(&exp), infoSink, &tempConstArray[i]))
+                  return nullptr;
+                break;
+              case EOpLog:
+                // For log(x), results are undefined if x <= 0, we are choosing to set result to 0.
+                if (getType().getBasicType() == EbtFloat && unionArray[i].getFConst() <= 0.0)
+                    tempConstArray[i].setFConst(0.0);
+                else if (!foldFloatTypeUnary(unionArray[i], static_cast<FloatTypeUnaryFunc>(&log), infoSink, &tempConstArray[i]))
+                    return nullptr;
+                break;
+              case EOpExp2:
+                if (!foldFloatTypeUnary(unionArray[i], static_cast<FloatTypeUnaryFunc>(&exp2), infoSink, &tempConstArray[i]))
+                    return nullptr;
+                break;
+              case EOpLog2:
+                // For log2(x), results are undefined if x <= 0, we are choosing to set result to 0.
+                if (getType().getBasicType() == EbtFloat && unionArray[i].getFConst() <= 0.0)
+                    tempConstArray[i].setFConst(0.0);
+                else if (!foldFloatTypeUnary(unionArray[i], static_cast<FloatTypeUnaryFunc>(&log2), infoSink, &tempConstArray[i]))
+                    return nullptr;
+                break;
+              case EOpSqrt:
+                // For sqrt(x), results are undefined if x < 0, we are choosing to set result to 0.
+                if (getType().getBasicType() == EbtFloat && unionArray[i].getFConst() < 0.0)
+                    tempConstArray[i].setFConst(0.0);
+                else if (!foldFloatTypeUnary(unionArray[i], static_cast<FloatTypeUnaryFunc>(&sqrt), infoSink, &tempConstArray[i]))
+                    return nullptr;
+                break;
+              case EOpInverseSqrt:
+                // There is no stdlib built-in function equavalent for GLES built-in inversesqrt(),
+                // so getting the square root first using builtin function sqrt() and then taking its inverse.
+                // Also, for inversesqrt(x), results are undefined if x <= 0, we are choosing to set result to 0.
+                if (getType().getBasicType() == EbtFloat && unionArray[i].getFConst() <= 0.0)
+                    tempConstArray[i].setFConst(0.0);
+                else if (!foldFloatTypeUnary(unionArray[i], static_cast<FloatTypeUnaryFunc>(&sqrt), infoSink, &tempConstArray[i]))
+                    return nullptr;
+                else
+                    tempConstArray[i].setFConst(1 / tempConstArray[i].getFConst());
+                break;
              default:
                return NULL;
            }