commit 3eeed90f7f73eac8d83e25c4ba756f5164c0600f
author Lei Zhang <antiagainst@google.com> Wed Jul 28 14:07:47 2021 -0400
committer GitHub <noreply@github.com> Wed Jul 28 11:07:47 2021 -0700
tree a3548401b893aa9853d1edd58e191062946e1ba1
parent 47238df8198e06fcaf41858114fdac5d6c1ba4dc

[spirv] Create variables early for conversion and deduplication (#6574)

`hal.interface.binding.subspan` to `spv.GlobalVariable` conversion
is tricky due to their different scopes (function vs. module),
SSA values vs. symbols, and the need to attach `alias` decorations.

Previously we create `spv.GlobalVariable` in the middle of the
conversion procedure, it requires us to pass down a few data
structures to the pattern so that we can access the alias
status. Notably, it requires us to pass in a `SymbolTable` so
that we can unique symbols. The `SymbolTable` needs to be created
before the conversion; otherwise we will see errors. It's relying
on `SymbolTable` and conversion framework implementation details;
so quite opaque.

This commit changes to create the global variables earlier, at the
alias analysis step. Then during conversion, we just need to
look up the table and perform mechanical rewrite, plus type fixup.
This limits all the `SymbolTable` access to a much smaller scope.
More importantly, we can also perform some deduplication for
created global variables to generate smaller SPIR-V blobs.