Removes the limit on scalar replacement for the lagalization passes.
This is done by adding an option to the pass (and command line option)
to set the limit on maximum size of the composite that scalar
replacement is willing to divide.
Fixes#1494.
Currently in scalar replacement, we create a new variable for every
memeber of the composite being divided. It is often overkill, because
not all of those members will be used. This change will check which
elements are used and only create variable for the members that are
used.
This reduces the compile time for one set of shader from 248s to 165s.
Part of https://github.com/KhronosGroup/SPIRV-Tools/issues/1494.
Adds a scalar replacement pass. The pass considers all function scope
variables of composite type. If there are accesses to individual
elements (and it is legal) the pass replaces the variable with a
variable for each composite element and updates all the uses.
Added the pass to -O
Added NumUses and NumUsers to DefUseManager
Added some helper methods for the inst to block mapping in context
Added some helper methods for specific constant types
No longer generate duplicate pointer types.
* Now searches for an existing pointer of the appropriate type instead
of failing validation
* Fixed spec constant extracts
* Addressed changes for review
* Changed RunSinglePassAndMatch to be able to run validation
* current users do not enable it
Added handling of acceptable decorations.
* Decorations are also transfered where appropriate
Refactored extension checking into FeatureManager
* Context now owns a feature manager
* consciously NOT an analysis
* added some test
* fixed some minor issues related to decorates
* added some decorate related tests for scalar replacement
