Dx11 & Dx12 device startup (#861)

* Added CombinationUtil to produce combinations of flags
Used in Dx11 device creation making it fall back to release driver if debug driver is not found

* Made dx12 renderer startup similar to dx11 - testing multiple configs.

* Small improvements in naming.

* * Moved functionality to gfx from core
* Use FlagCombiner to simplify construction, and can be iterated over, without need for array
* Share DeviceCheckFlags

* Improve comments.

* Re-add the comment about combinations tested to set up dx11 device.

* More comment improvements.

1 files changed, 55 insertions, 0 deletions

diff --git a/tools/gfx/flag-combiner.cpp b/tools/gfx/flag-combiner.cpp
new file mode 100644
index 000000000..04617368a
--- /dev/null
+++ b/tools/gfx/flag-combiner.cpp
@@ -0,0 +1,55 @@
+#include "flag-combiner.h"
+
+namespace gfx {
+using namespace Slang;
+
+void FlagCombiner::add(uint32_t flags, ChangeType type)
+{
+    // The flag/s must be set
+    SLANG_ASSERT(flags);
+    SLANG_ASSERT((flags & m_usedFlags) == 0);
+    // Mark the flags used
+    m_usedFlags |= flags;
+
+    if (type == ChangeType::On || type == ChangeType::OnOff)
+    {
+        m_invertBits |= flags;
+    }
+    if (type == ChangeType::OnOff || type == ChangeType::OffOn)
+    {
+        m_changingBits[m_numChangingBits++] = flags;
+    }
+}
+
+void FlagCombiner::calcCombinations(List<uint32_t>& outCombinations) const
+{
+    const int numCombinations = getNumCombinations();
+    outCombinations.SetSize(numCombinations);
+    uint32_t* dstCombinations = outCombinations.Buffer();
+    for (int i = 0; i < numCombinations; ++i)
+    {
+        dstCombinations[i] = getCombination(i);
+    }
+}
+
+uint32_t FlagCombiner::getCombination(int index) const
+{
+    SLANG_ASSERT(index >= 0 && index < getNumCombinations());
+
+    uint32_t combination = 0;
+    uint32_t bit = 1;
+    for (int i = 0; i < m_numChangingBits; ++i, bit += bit)
+    {
+        combination |= ((bit & index) ? m_changingBits[i] : 0);
+    }
+    return combination ^ m_invertBits;
+}
+
+void FlagCombiner::reset()
+{
+    m_numChangingBits = 0;
+    m_usedFlags = 0;
+    m_invertBits = 0;
+}
+
+} // namespace gfx