Merge branch 'overloaded-400' of github.com:KhronosGroup/glslang

glslang/MachineIndependent/ParseContextBase.cpp

@@ -0,0 +1,184 @@
+//
+//Copyright (C) 2002-2005  3Dlabs Inc. Ltd.
+//Copyright (C) 2016 Google, Inc.
+//
+//All rights reserved.
+//
+//Redistribution and use in source and binary forms, with or without
+//modification, are permitted provided that the following conditions
+//are met:
+//
+//    Redistributions of source code must retain the above copyright
+//    notice, this list of conditions and the following disclaimer.
+//
+//    Redistributions in binary form must reproduce the above
+//    copyright notice, this list of conditions and the following
+//    disclaimer in the documentation and/or other materials provided
+//    with the distribution.
+//
+//    Neither the name of 3Dlabs Inc. Ltd. nor the names of its
+//    contributors may be used to endorse or promote products derived
+//    from this software without specific prior written permission.
+//
+//THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+//"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+//LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+//FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+//COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+//INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+//BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+//LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+//CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+//LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+//ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+//POSSIBILITY OF SUCH DAMAGE.
+//
+
+// Implement the TParseContextBase class.
+
+#include "ParseHelper.h"
+
+extern int yyparse(glslang::TParseContext*);
+
+namespace glslang {
+
+// Select the best matching function for 'call' from 'candidateList'.
+//
+// Assumptions
+//
+// There is no exact match, so a selection algorithm needs to run. That is, the
+// language-specific handler should check for exact match first, to
+// decide what to do, before calling this selector.
+//
+// Input
+//
+//  * list of candidate signatures to select from
+//  * the call
+//  * a predicate function convertible(from, to) that says whether or not type
+//    'from' can implicitly convert to type 'to' (it includes the case of what
+//    the calling language would consider a matching type with no conversion
+//    needed)
+//  * a predicate function better(from1, from2, to1, to2) that says whether or
+//    not a conversion from <-> to2 is considered better than a conversion
+//    from <-> to1 (both in and out directions need testing, as declared by the
+//    formal parameter)
+//
+// Output
+//
+//  * best matching candidate (or none, if no viable candidates found)
+//  * whether there was a tie for the best match (ambiguous overload selection,
+//    caller's choice for how to report)
+//
+const TFunction* TParseContextBase::selectFunction(
+    TVector<const TFunction*> candidateList,
+    const TFunction& call,
+    std::function<bool(const TType& from, const TType& to)> convertible,
+    std::function<bool(const TType& from, const TType& to1, const TType& to2)> better,
+    /* output */ bool& tie)
+{
+// 
+// Operation
+// 
+// 1. Prune the input list of candidates down to a list of viable candidates,
+// where each viable candidate has
+// 
+//  * at least as many parameters as there are calling arguments, with any
+//    remaining parameters being optional or having default values
+//  * each parameter is true under convertible(A, B), where A is the calling
+//    type for in and B is the formal type, and in addition, for out B is the
+//    calling type and A is the formal type
+// 
+// 2. If there are no viable candidates, return with no match.
+// 
+// 3. If there is only one viable candidate, it is the best match.
+//
+// 4. If there are multiple viable candidates, select the first viable candidate
+// as the incumbent. Compare the incumbent to the next viable candidate, and if
+// that candidate is better (bullets below), make it the incumbent. Repeat, with
+// a linear walk through the viable candidate list. The final incumbent will be
+// returned as the best match. A viable candidate is better than the incumbent if
+// 
+//  * it has a function argument with a better(...) conversion than the incumbent,
+//    for all directions needed by in and out
+//  * the incumbent has no argument with a better(...) conversion then the
+//    candidate, for either in or out (as needed)
+//
+// 5. Check for ambiguity by comparing the best match against all other viable
+// candidates. If any other viable candidate has a function argument with a
+// better(...) conversion than the best candidate (for either in or out
+// directions), return that there was a tie for best.
+//
+
+    tie = false;
+
+    // 1. prune to viable...
+    TVector<const TFunction*> viableCandidates;
+    for (auto it = candidateList.begin(); it != candidateList.end(); ++it) {
+        const TFunction& candidate = *(*it);
+
+        // to even be a potential match, number of arguments has to match
+        if (call.getParamCount() != candidate.getParamCount())
+            continue;
+
+        // see if arguments are convertible
+        bool viable = true;
+        for (int param = 0; param < candidate.getParamCount(); ++param) {
+            if (candidate[param].type->getQualifier().isParamInput()) {
+                if (! convertible(*call[param].type, *candidate[param].type)) {
+                    viable = false;
+                    break;
+                }
+            }
+            if (candidate[param].type->getQualifier().isParamOutput()) {
+                if (! convertible(*candidate[param].type, *call[param].type)) {
+                    viable = false;
+                    break;
+                }
+            }
+        }
+
+        if (viable)
+            viableCandidates.push_back(&candidate);
+    }
+
+    // 2. none viable...
+    if (viableCandidates.size() == 0)
+        return nullptr;
+
+    // 3. only one viable...
+    if (viableCandidates.size() == 1)
+        return viableCandidates.front();
+
+    // 4. find best...
+    auto betterParam = [&call, &better](const TFunction& can1, const TFunction& can2){
+        // is call -> can2 better than call -> can1 for any parameter
+        bool hasBetterParam = false;
+        for (int param = 0; param < call.getParamCount(); ++param) {
+            if (better(*call[param].type, *can1[param].type, *can2[param].type)) {
+                hasBetterParam = true;
+                break;
+            }
+        }
+        return hasBetterParam;
+    };
+
+    const TFunction* incumbent = viableCandidates.front();
+    for (auto it = viableCandidates.begin() + 1; it != viableCandidates.end(); ++it) {
+        const TFunction& candidate = *(*it);
+        if (betterParam(*incumbent, candidate) && ! betterParam(candidate, *incumbent))
+            incumbent = &candidate;
+    }
+
+    // 5. ambiguity...
+    for (auto it = viableCandidates.begin(); it != viableCandidates.end(); ++it) {
+        if (incumbent == *it)
+            continue;
+        const TFunction& candidate = *(*it);
+        if (betterParam(*incumbent, candidate))
+            tie = true;
+    }
+
+    return incumbent;
+}
+
+} // end namespace glslang