Implements
https://github.com/llvm/wg-hlsl/blob/main/proposals/0026-symbol-visibility.md.
The change is to stop using the `hlsl.export` attribute. Instead,
symbols with "program linkage" in HLSL will have export linkage with
default visibility, and symbols with "external linkage" in HLSL will
have export linkage with hidden visibility.
To consolidate behavior of function mangling and limit the number of
places that ABI changes will need to be made, this switches the DirectX
target used for HLSL to use the Itanium ABI from the Microsoft ABI. The
Itanium ABI has greater flexibility in decisions regarding mangling of
new types of which we have more than a few yet to add.
One effect of this will be that linking library shaders compiled with
DXC will not be possible with shaders compiled with clang. That isn't
considered a terribly interesting use case and one that would likely
have been onerous to maintain anyway.
This involved adding a function to call all global destructors as the
Microsoft ABI had done.
This requires a few changes to tests. Most notably the mangling style
has changed which accounts for most of the changes. In making those
changes, I took the opportunity to harmonize some very similar tests for
greater consistency. I also shaved off some unneeded run flags that had
probably been copied over from one test to another.
Other changes effected by using the new ABI include using different
types when manipulating smaller bitfields, eliminating an unnecessary
alloca in one instance in this-assignment.hlsl, changing the way static
local initialization is guarded, and changing the order of inout
parameters getting copied in and out. That last is a subtle change in
functionality, but one where there was sufficient inconsistency in the
past that standardizing is important, but the particular direction of
the standardization is less important for the sake of existing shaders.
fixes#110736
We already infer this in IPSCCP (which runs very early, so cannot
benefit from inlining and simplifications) and SCCP (which runs without
PredicateInfo, so does not use assumes). Do it in CVP as well, so it can
handle cases that IPSCCP/SCCP can't.
Fixes https://github.com/llvm/llvm-project/issues/98946 (everything
apart from f2, where the assume is dropped by the frontend).
HLSL output parameters are denoted with the `inout` and `out` keywords
in the function declaration. When an argument to an output parameter is
constructed a temporary value is constructed for the argument.
For `inout` pamameters the argument is initialized via copy-initialization
from the argument lvalue expression to the parameter type. For `out`
parameters the argument is not initialized before the call.
In both cases on return of the function the temporary value is written
back to the argument lvalue expression through an implicit assignment
binary operator with casting as required.
This change introduces a new HLSLOutArgExpr ast node which represents
the output argument behavior. The OutArgExpr has three defined children:
- An OpaqueValueExpr of the argument lvalue expression.
- An OpaqueValueExpr of the copy-initialized parameter.
- A BinaryOpExpr assigning the first with the value of the second.
Fixes#87526
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Co-authored-by: Damyan Pepper <damyanp@microsoft.com>
Co-authored-by: John McCall <rjmccall@gmail.com>
