[SPIRV][SPIRVPrepareGlobals] Convert llvm.embedded.module from a 0-element array to a 1-element array (#166950)

When compiling with `-fembed-bitcode-marker`, Clang inserts a
placeholder
for the bitcode. This placeholder is a `[0 x i8]` array, which we cannot
represent in SPIRV.

For AMD flavored SPIRV, we extend the `llvm.embedded.module` global to a
`zeroinitializer [1 x i8]` array.

To achieve this, this patch adds a new pass, `SPIRVPrepareGlobals`, that
we can use to write global variable's _non-trivial-to-lower-IR_ ->
_trivial-to-lower-IR_ mappings.

This is a second attempt at
https://github.com/llvm/llvm-project/pull/162082, but cleaner.

In the translator something similar is done for every 0-element array
since https://github.com/KhronosGroup/SPIRV-LLVM-Translator/pull/2743 .
But I don't think we want to do this mapping for all cases.

0 files changed, 0 insertions, 0 deletions