AvailabilityDiagnostics.rst and ExpectedDifferences.rst both had
multiple headers that were perceived to be the "top-level".
In AvailabilityDiagnostics.rst two headers had both over and underlines.
The second was the "Examples" section so it showed up in the top level
HLSL docs. The overline is removed here so it's clear it's a subheader.
In ExpectedDifferences.rst, the first header had no overline, so a few
headers that looked the same were included. The overline is added to the
top header to make clear that it's the main header.
This PR reworks HLSL's implicit conversion sequences. Initially I was
seeking to match DXC's behavior more closely, but that was leading to a
pile of special case rules to tie-break ambiguous cases that should
really be left as ambiguous. We've decided that we're going to break
compatibility with DXC here, and we may port this new behavior over to
DXC instead.
This change is a bit closer to C++'s overload resolution rules, but it
does have a bit of nuance around how dimension adjustment conversions
are ranked. Conversion sequence ranks for HLSL are:
* Exact match
* Scalar Widening (i.e. splat)
* Promotion
* Scalar Widening with Promotion
* Conversion
* Scalar Widening with Conversion
* Dimension Reduction (i.e. truncation)
* Dimension Reduction with Promotion
* Dimension Reduction with Conversion
In this implementation I've folded the disambiguation into the
conversion sequence ranks which does add some complexity as compared to
C++, however this avoids needing to add special casing in
`CompareStandardConversionSequences`. I believe the added conversion
rank values provide a simpler approach, but feedback is appreciated.
The HLSL language spec updates are in the PR here:
https://github.com/microsoft/hlsl-specs/pull/261
This document covers expected differences between Clang and the HLSL
reference compiler implementations (FXC & DXC). The document is not
intended to be exhaustive, but it should be a best effort to cover known
cases.
This document should document both the behavioral difference and the
explanation of why Clang differs.
The initail document covers known overload resolution differences.
---------
Co-authored-by: S. Bharadwaj Yadavalli <Bharadwaj.Yadavalli@microsoft.com>
