Capabilities System, CapabilitySet Logic Overhaul (shader-slang#4145)

* Capabilities System, Backing Logic Overhaul

Fixes shader-slang#4015

Problems to address:
1. Currently the capabilities system spends anywhere from 25-50% of compile time on the CapabilityVisitor. Most of this time is spent on join logic: 1. Finding abstract atoms 2. Comparing list1<->list2. This should and can be made significantly faster.
2. Error system does not produce errors with auxiliary information. This will require a partial redesign to provide more useful semantic information for debugging.

What was addressed:
1. Array backed `CapabilityConjunctionSet` was replaced in-favor for a `UIntSet` backed `CapabilityTargetSets`. The design is described below.
Design:
* `CapabilityTargetSets` is a `Dictionary<targetAtom, CapabilityTargetSet>`. This is not an array for 2 reasons: 1. Easy to figure out which target is missing between two `CapabilityTargetSets` 2. To statically allocate an array requires the preprocessor to manually annotate which Capability is a target and link that Capability to an index. This means a dictionary is required for lookup regardless of implementation.
* `CapabilityTargetSet` is an intermediate representation of all capabilities for a singular `target` atom (`glsl`, `hlsl`, `metal`, ...). This structure contains a dictionary to all stage specific capability sets for fast lookup of stage capabilities supported by a `CapabilitySet` for a `target` atom. This reduces number of sets searched.
* `CapabilityStageSet` is an intermediate representation of all capabilities for a singular `stage` atom (`vertex`, `fragment`, ...). This structure holds all disjoint capability sets for a `stage`. A disjoint set is rare, but may exist in some scenarios (as an example): `{glsl, EXT_GL_FOO}{glsl, _GLSL_130, _GLSL_150}`. This reduces the number of sets searched.
* `UIntSet` is the main reason for the redesign for better performance and memory usage. All set operations only require a few operations, making all set logic trivial and with minimal cost to run. All algorithms were modified to focus around `UIntSet` operations.

2. Errors
* Semantic information are now better linked to the calling function to provide a connection of function<->function_body for when saving semantic information for errors.
* Missing targets now print errors much like other error code by finding code which could be a cause of incompatibility.

What is missing:
1. Add non naive support for non-stage specific capabilities such as `{hlsl, _sm_5_0}`. Currently non stage specific targets emulate the behavior through assigning such capabilities to every stage: `{hlsl, _sm_5_0, vertex} {hlsl, _sm_5_0, fragment}...`. Removal of this behavior would remove redundant shader stage sets being made at construction time (~80% of new implementation runtime). This is an addition, not an overhaul.
2. Optionally: `UIntSet` should be modified to support SIMD operations for significantly faster operations. This is not required immediately since `UIntSet` is already not a performance constraint.

Notes:
* UIntSet had implementation bugs which were fixed in this PR.
* The old capabilities system had bugs which were fixed in this PR when transforming to the new implementation.

* fix .natvis debug view

* Small optimizations I found while working on the addition

the AST building pass looks like so now:
1% = ~capabilitySet
2% = capabilitySet()
1.5% capabilitySet::unionWith()
0.8% capabilitySet::join()
1.5% auxillary info for debugging
~0.5-1% extra visitor overhead

~5% total for the visitor
~6.5% for total runtime costs

* fix caps which were wrong but worked

* push minor syntax fix (still looking for why other tests fail)

* perf & bug fixes

1. did not properly remake isBetterForTarget for this->empty case with that as Invalid. This is best case in this senario.
2. Remade seralizer for stdlib generation. Faster (more direct) & cleaner code.

NOTE: did not address review comments

* fix glsl.meta caps error

* fixing findBest logic again & UIntSet wrapper

findBest was not checking for 'more specialized' targets & was element counter was flawed

* faster getElements algorithm + natvis for UIntSet + wrong warning

* type incompatability of bitscanForward implementations

* try to fix warnings again

* remove ptr for clang intrinsic

* add missing header

* ifdef to allow clang compile

* compiler hackery to fix up platform/type independent operations

* bracket

* fix MSVC error

* missing template

* change types out again

* changes to fix compiling

* adjustment to parameter for Clang/GCC

* added iterator to delay processing all atomSets of a CapabilitySet

* add a few missing consts's

* ensure we never have more than 1 disjointSet

Added a wrapper + assert + union functionality to all possible disjoint sets. This was done in favor of a removal of the LinkedList for 2 reasons:
1. We still need 0-1 set functionality.
2. Might as well keep the code, just disallow the problematic functionality.

* address review comments

non linked-list refactor review comments addressed; add doc comments + remove redundant code

* comments + remove isValid for bool operator

* push removal of linkedlist for capabilities

* add missing break

* address review comments

minor adjustments of syntax

* push a fix to the `CapabilitySet({shader, missing target})` code

* quality + error

1. add iterator to UIntSet
2. do not specialize target_switch if profile is derived from case (GLSL_150 is not compatable with GLSL_400)

* fix target_switch erroring + temporarily remove UIntSet::Interator

temporarily remove UIntSet::Interator. It will be added after, testing code on CI first so I can multi-task fixing the UIntSet Iterator

* fix the UIntSet iterator

* Revert "fix the UIntSet iterator" temporarily to pull from master

* add metal error as per texture.slang

(took a while I realize this was why things were breaking, likely should adjust errors to reflect this)

* Rework UIntSet to have a template for output type

This is done so it is reasonable to debug the iterator output and not just dealing with messy int's

Fix problems with the iterators implemented + invalid capabilities handling

* removed incorrect `__target_switch` capability

barycentric was being used with anticipation of `profile glsl450`, this does not expand into `GL_EXT_fragment_shader_barycentric`, this instead caused an error which is hidden during cross-compile.

* remove some uses of getElements

* remove undeclared_stage for now

* remove redundant code associated with `undeclared_stage`

* remove unused variable

* address review

specifically to note removed static in a thread dangerous scope. Now using a `const static` for read only (thread safe) which precompile steps generate

* move GLSL_150 capdef change to sm_4_1 (more accurate)

* address most review comments

did not address: shader-slang#4145 (comment)

* revert incorrect code review suggestion

* push changes for all code review suggestions

Author: ArielG-NV

source/core/slang-linked-list.h

@@ -323,7 +323,7 @@ template <typename T> class LinkedList
         }
         return rs;
     }
-    int getCount() { return count; }
+    int getCount() const { return count; }
 };
 } // namespace Slang
 #endif

source/core/slang-uint-set.cpp

@@ -3,18 +3,6 @@
 namespace Slang
 {
 
-static bool _areAllZero(const UIntSet::Element* elems, Index count)
-{
-    for (Index i = 0; count; ++i)
-    {
-        if (elems[i])
-        {
-            return false;
-        }
-    }
-    return true;
-}
-
 UIntSet& UIntSet::operator=(UIntSet&& other)
 {
     m_buffer = _Move(other.m_buffer);
@@ -49,14 +37,8 @@ void UIntSet::setAll()
 
 void UIntSet::resize(UInt size)
 {
-    const Index oldCount = m_buffer.getCount();
     const Index newCount = Index((size + kElementMask) >> kElementShift);
-    m_buffer.setCount(newCount);
-
-    if (newCount > oldCount)
-    {
-        ::memset(m_buffer.getBuffer() + oldCount, 0, (newCount - oldCount) * sizeof(Element));
-    }
+    resizeBackingBufferDirectly(newCount);
 }
 
 void UIntSet::clear()
@@ -66,17 +48,7 @@ void UIntSet::clear()
 
 bool UIntSet::isEmpty() const
 {
-    const Element*const src = m_buffer.getBuffer();
-    const Index count = m_buffer.getCount();
-
-    for (Index i = 0; i < count; ++i)
-    {
-        if (src[i])
-        {
-            return false;
-        }
-    }
-    return true;
+    return _areAllZero(m_buffer.getBuffer(), m_buffer.getCount());
 }
 
 void UIntSet::clearAndDeallocate()
@@ -106,7 +78,7 @@ bool UIntSet::operator==(const UIntSet& set) const
 
     const Index minCount = Math::Min(aCount, bCount);
 
-    return ::memcmp(aElems, bElems, minCount) == 0 &&
+    return ::memcmp(aElems, bElems, minCount*sizeof(Element)) == 0 &&
         _areAllZero(aElems + minCount, aCount - minCount) &&
         _areAllZero(bElems + minCount, bCount - minCount);
 }
@@ -123,6 +95,15 @@ void UIntSet::intersectWith(const UIntSet& set)
     }
 }
 
+void UIntSet::subtractWith(const UIntSet& set)
+{
+    const Index minCount = Math::Min(this->m_buffer.getCount(), set.m_buffer.getCount());
+    for (Index i = 0; i < minCount; i++)
+    {
+        this->m_buffer[i] = this->m_buffer[i] & (~set.m_buffer[i]);
+    }
+}
+
 /* static */void UIntSet::calcUnion(UIntSet& outRs, const UIntSet& set1, const UIntSet& set2)
 {
     outRs.m_buffer.setCount(Math::Max(set1.m_buffer.getCount(), set2.m_buffer.getCount()));
@@ -162,5 +143,24 @@ void UIntSet::intersectWith(const UIntSet& set)
     return false;
 }
 
+Index UIntSet::countElements() const
+{
+    // TODO: This can be made faster using SIMD intrinsics to count set bits.
+    uint64_t tmp;
+    constexpr Index loopSize = ((sizeof(Element) / sizeof(tmp)) != 0) ? sizeof(Element) / sizeof(tmp) : 1;
+    Index count = 0;
+    for (auto index = 0; index < this->m_buffer.getCount(); index++)
+    {
+        for (auto i = 0; i < loopSize; i++)
+        {
+            tmp = m_buffer[index] >> (sizeof(tmp) * i);
+            tmp = tmp - ((tmp >> 1) & 0x5555555555555555);
+            tmp = (tmp & 0x3333333333333333) + ((tmp >> 2) & 0x3333333333333333);
+            count += ((tmp + (tmp >> 4) & 0xF0F0F0F0F0F0F0F) * 0x101010101010101) >> 56;
+        }
+    }
+    return count;
+}
+
 }