1//
2// Copyright (c) 2017 The ANGLE Project Authors. All rights reserved.
3// Use of this source code is governed by a BSD-style license that can be
4// found in the LICENSE file.
5//
6// ClampFragDepth.cpp: Limit the value that is written to gl_FragDepth to the range [0.0, 1.0].
7// The clamping is run at the very end of shader execution, and is only performed if the shader
8// statically accesses gl_FragDepth.
9//
10
11#include "compiler/translator/tree_ops/ClampFragDepth.h"
12
13#include "compiler/translator/ImmutableString.h"
14#include "compiler/translator/SymbolTable.h"
15#include "compiler/translator/tree_util/BuiltIn_autogen.h"
16#include "compiler/translator/tree_util/FindSymbolNode.h"
17#include "compiler/translator/tree_util/IntermNode_util.h"
18#include "compiler/translator/tree_util/RunAtTheEndOfShader.h"
19
20namespace sh
21{
22
23void ClampFragDepth(TIntermBlock *root, TSymbolTable *symbolTable)
24{
25 // Only clamp gl_FragDepth if it's used in the shader.
26 if (!FindSymbolNode(root, ImmutableString("gl_FragDepth")))
27 {
28 return;
29 }
30
31 TIntermSymbol *fragDepthNode = new TIntermSymbol(BuiltInVariable::gl_FragDepth());
32
33 TIntermTyped *minFragDepthNode = CreateZeroNode(TType(EbtFloat, EbpHigh, EvqConst));
34
35 TConstantUnion *maxFragDepthConstant = new TConstantUnion();
36 maxFragDepthConstant->setFConst(1.0);
37 TIntermConstantUnion *maxFragDepthNode =
38 new TIntermConstantUnion(maxFragDepthConstant, TType(EbtFloat, EbpHigh, EvqConst));
39
40 // clamp(gl_FragDepth, 0.0, 1.0)
41 TIntermSequence *clampArguments = new TIntermSequence();
42 clampArguments->push_back(fragDepthNode->deepCopy());
43 clampArguments->push_back(minFragDepthNode);
44 clampArguments->push_back(maxFragDepthNode);
45 TIntermTyped *clampedFragDepth =
46 CreateBuiltInFunctionCallNode("clamp", clampArguments, *symbolTable, 100);
47
48 // gl_FragDepth = clamp(gl_FragDepth, 0.0, 1.0)
49 TIntermBinary *assignFragDepth = new TIntermBinary(EOpAssign, fragDepthNode, clampedFragDepth);
50
51 RunAtTheEndOfShader(root, assignFragDepth, symbolTable);
52}
53
54} // namespace sh
55