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<title>slang.git/source/slang/ir-clone.cpp, branch master</title>
<subtitle>Making it easier to work with shaders</subtitle>
<id>https://git.yummers.dev/slang.git/atom?h=master</id>
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<updated>2019-05-31T21:20:37+00:00</updated>
<entry>
<title>Use slang- prefix on slang compiler and core source (#973)</title>
<updated>2019-05-31T21:20:37+00:00</updated>
<author>
<name>jsmall-nvidia</name>
<email>jsmall@nvidia.com</email>
</author>
<published>2019-05-31T21:20:37+00:00</published>
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<id>urn:sha1:6cbc3929a54d37bd23cb5efa8e3320ba02f78b2f</id>
<content type='text'>
* Prefixing source files in source/slang with slang-

* Prefix source in source/slang with slang- prefix.

* Rename core source files with slang- prefix.

* Update project files.

* Fix problems from automatic merge.
</content>
</entry>
<entry>
<title>String/List closer to conventions, and use Index type (#959)</title>
<updated>2019-04-29T21:03:46+00:00</updated>
<author>
<name>jsmall-nvidia</name>
<email>jsmall@nvidia.com</email>
</author>
<published>2019-04-29T21:03:46+00:00</published>
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<id>urn:sha1:4880789e3003441732cca4471091563f36531635</id>
<content type='text'>
* List made members m_
Tweaked types to closer match conventions.

* Use asserts for checking conditions on List.
Other small improvements.

* List&lt;T&gt;.Count() -&gt; getSize()

* List&lt;T&gt;
Add -&gt; add
First -&gt; getFirst
Last -&gt; getLast
RemoveLast -&gt; removeLast
ReleaseBuffer -&gt; detachBuffer
GetArrayView -&gt; getArrayView

* List&lt;T&gt;::
AddRange -&gt; addRange
Capacity -&gt; getCapacity
Insert -&gt; insert
InsertRange -&gt; insertRange
AddRange -&gt; addRange
RemoveRange -&gt; removeRange
RemoveAt -&gt; removeAt
Remove -&gt; remove
Reverse -&gt; reverse
FastRemove -&gt; fastRemove
FastRemoveAt -&gt; fastRemoveAt
Clear -&gt; clear

* List&lt;T&gt;
FreeBuffer -&gt; _deallocateBuffer
Free -&gt; clearAndDeallocate
SwapWith -&gt; swapWith

* List&lt;T&gt;
SetSize -&gt; setSize
Reserve -&gt; reserve
GrowToSize growToSize

* UnsafeShrinkToSize -&gt; unsafeShrinkToSize
Compress -&gt; compress
FindLast -&gt; findLastIndex
FindLast -&gt; findLastIndex
Simplify Contains

* List&lt;T&gt;
Removed m_allocator (wasn't used)
Swap -&gt; swapElements
Sort -&gt; sort
Contains -&gt; contains
ForEach -&gt; forEach
QuickSort -&gt; quickSort
InsertionSort -&gt; insertionSort
BinarySearch -&gt; binarySearch

Max -&gt; calcMax
Min -&gt; calcMin

* Initializer::Initialize -&gt; initialize
List&lt;T&gt;::
Allocate -&gt; _allocate
Init -&gt; _init
IndexOf -&gt; indexOf

* * Put #include &lt;assert.h&gt; in common.h, and remove unneeded inclusions
* Small refactor of ArrayView - remove stride as not used

* getSize -&gt; getCount
setSize -&gt; setCount
unsafeShrinkToSize-&gt;unsafeShrinkToCount
growToSize -&gt; growToCount
m_size -&gt; m_count

* Some tidy up around Allocator.

* Use Index type on List.

* Refactor of IntSet.
First tentative look at using Index.

* Made Index an Int
Did preliminary fixes.
Made String use Index.

* Partial refactor of String.

* String::Buffer -&gt; getBuffer
ToWString -&gt; toWString

* Small improvements to String.
String::
Buffer() -&gt; getBuffer()
Equals() -&gt; equals

* Try to use Index where appropriate.

* Fix warnings on windows x86 builds.
</content>
</entry>
<entry>
<title>Initial support for the `precise` keyword (#958)</title>
<updated>2019-04-29T16:31:25+00:00</updated>
<author>
<name>Tim Foley</name>
<email>tfoleyNV@users.noreply.github.com</email>
</author>
<published>2019-04-29T16:31:25+00:00</published>
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<id>urn:sha1:ded340beb4b5197b559626acc39920abb2d39e77</id>
<content type='text'>
Fixes #858

The `precise` keyword exists in both HLSL and GLSL and when applied to a variable declaration is supposed to indicate that all computations that contribute to the value of that variable should not be altered based on "fast-math" optimizations. The main examples are that separate multiply and add operations should not be turned into fused multiply-add (fma) operations, and that operations cannot ignore the possibility of infinity or not-a-number values (e.g., by assuming that `x * 0.0f` is always `0.0f`).

(Aside: it is possible that my understanding of what the semantics of `precise` are in HLSL and GLSL is imperfect so that either the GLSL variant isn't sufficient to provide the semantics of the HLSL keyword, or that the definition of "all computations that contribute" to a value isn't actually correct. We may need to revise this implementation based on subsequent learnings.)

The basic idea here is to turn the AST `precise` keyword into a `[precise]` decoration in the IR and then emit that as a `precise` keyword again in the output.

The main catch is that whereas most of our existing IR decorations apply to things like global shader parameters or `struct` members that usually stick around for the duration of compilation, `[precise]` will get slapped on local variables that will often get optimized away by our SSA pass. There are two ways a variable can get eliminated/replaced during the SSA pass:

1. A use of the variable can be replaced with an ordinary instruction that computes its value.
2. A use of the variable can be replaced with a reference to a "phi node" that will take on the appropriate value based on control flow.

These two cases already had logic to copy a "name hint" decoration from the variable over to an instruction that will replace it, and I simply extended them to also propagate over a `[precise]` decoration.

The test case added with this change intentionally constructs a case where `[precise]` needs to be propagated over to an SSA "phi node" in order to generate correct output code.

The other gotcha is that we can emit variable declarations in various places in `emit.cpp`, and all of these needed to handle `[precise]`. Not only do we have actually local variables (`IRVar`), but we also have SSA phi nodes (`IRParam`), and then there are cases where an intermediate computation (an ordinary instruction) should be `[precise]` and thus we need to emit it as a temporary (not folding it into its use sites) and make sure that the temporary itself gets the `precise` keyword.

I have manually confirmed that in the output SPIR-V, this change results in the `NoContraction` SPIR-V decoration being added to the relevant operations, and the output DXBC contains a multiply and an add in place of a multiply-add. The output DXIL does not show any obvious changes due to `precise`, although the exact order and operands of the math instructions emitted does differ when `precise` is added/removed. In all cases the output is equivalent to hand-written HLSL/GLSL with a `precise`-qualified local variable.</content>
</entry>
<entry>
<title>Add better control over image formats for GLSL/SPIR-V targets (#939)</title>
<updated>2019-04-08T18:09:03+00:00</updated>
<author>
<name>Tim Foley</name>
<email>tfoleyNV@users.noreply.github.com</email>
</author>
<published>2019-04-08T18:09:03+00:00</published>
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<id>urn:sha1:dc54f1dd1b694b087816857a791e9d37dc25de6d</id>
<content type='text'>
* Add better control over image formats for GLSL/SPIR-V targets

Currently Slang emits GLSL code assuming all R/W images need to have explicit formats, and thus we try to infer a format from the element type of the image.
E.g., given a `RWTexture2D&lt;half4&gt;` we might infer that a qualifier of `layout(rgba16f)` should be used.

This strategy has two notable shortcomings:

* Sometimes the user will want a format that doesn't match an existing HLSL type. E.g., if they want the equivalent of `layout(r11f_g11f_b10f)`, then what should they put in their `RWTexture2D&lt;...&gt;` to make the inference do what they need?

* Sometimes the user knows that they don't need to specify a format *at all*, because using the `GL_EXT_shader_image_load_formatted` extension, they can still perform non-atomic load/store on images with no format specified in the SPIR-V.

This change adds two features directed at these challenges.

First, we add an explicit `[format(...)]` attribute that can be used to specify an explicit image format, including ones that don't match any HLSL type.
An example of using this new attribute is:

```hlsl
[format("r11f_g11f_b10f")]
RWTexture2D&lt;float3&gt; myImage;
```

For simplicity in initial bring-up, the new formats all use the same naming as formats in GLSL (this should make it easy for a programmer who knows what they expect to get in the GLSL output). We can change the naming convention for formats at a later time, so long as we keep these existing names in as a compatibility feature.

Note that this is *not* given a `vk::` prefix since the attribute should signal the programmer's intent to provide an image with that format on *all* targets (although only some targets might act on that information).

Also note that the attribute takes a string (`[format("rgba8")`) instead of a bare identifier (`[format(rgba8)]`) because this is consistent with the existing convention for attributes in HLSL.

When `[format(...)]` is left off, the default compiler behavior will still be to infer a format, but this behavior can be overidden for a single image using an explicit format of `"unknown"`:

```hlsl
[format("unknown")]
RWTexture2D&lt;float4&gt; mysteryMachine;
```

The second new feature is that if a user knows they are coding for a GPU that supports the `"unknown"` format in all non-atomic cases, then they can opt into making that the default for images without an explicit `[format(...)]`, using the new `-default-image-format-unknown` command-line option for `slangc`.

The new test case included with this change confirms that we correctly see the explicit formats in the output GLSL and *no* formats for images without explicit `[format(...)]` when using the new command-line option. The test stresses images declared at global scope, in parameter blocks, and in entry-point parameter lists, to try and make sure that all the relevant IR passes in the compiler preserve the format information.

* fixup: missing file
</content>
</entry>
<entry>
<title>Refactor several IR passes (#761)</title>
<updated>2018-12-19T22:38:04+00:00</updated>
<author>
<name>Tim Foley</name>
<email>tfoleyNV@users.noreply.github.com</email>
</author>
<published>2018-12-19T22:38:04+00:00</published>
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<id>urn:sha1:332056a947ec3d9e3588a60d449d64577a6f18c0</id>
<content type='text'>
* Refactor several IR passes

This change takes some IR passes that lived together in `ir.cpp` and moves them into their own files to improve clarity.
In most cases these were passes introduced early in the life of the IR, so that it didn't seem like a big deal to have them all in one file, but now that `ir.cpp` has grown unwieldly this seems like an important cleanup to make.

To give a quick rundown of the passes involved:

* The IR "linking" step has been pulled out to `ir-link.{h,cpp}`. This code for this pass is pretty much identical to what was in `ir.cpp`, and no attempt has been made to clean up or refactor it in the current change.

* The GLSL legalization step has been pulled out to `ir-glsl-legalize.{h,cpp}`. This used to be invoked directly from the linking step, but has been made a new top-level pass invoked from `emit.cpp`. Just like with the linking, the code in the new file is just a copy-paste of what was in `ir.cpp`, and no attempt at cleanup has been made. Also note that it might be a good idea to move this pass later in the overall sequence, but this PR doesn't attempt to do that as it could change results.

* The generic specialization step has been pulled out to `ir-specialize.{h,cpp}`. The file name does not explicitly reference *generic* specialization because I anticipate this pass having to perform other kinds of specialization as well. The code in this case amounts to a heavy cleanup/refactoring pass and  thus deserves careful scrutiny. The reason for the cleanup is that the generic specialization step used to be part of the "linking" step long ago, and continued to share infrastructure with it long after that stopped making sense. The newly cleaned up pass has much simpler logic that should be easy enough to follow from the comments.

* In order to reduce code dulication, the IR "cloning" part of the `ir-specialize-resources.{h,cpp}` pass was pulled into its own files (`ir-clone.{h,cpp}`) that both the generic specialization step and the resource-based specialization step now share.

The remaining changes then pertain to deleting a bunch of code out of `ir.cpp` and adding the new files to the build.

The only test that needed updating was `vkray/raygen`, where some subtle ordering change in the refactored generic specialization logic has lead to the relative order of the specialized `TraceRay` and `saturate` functions beind reversed.

* fixup: typo in assert

* fixup: typos in comments
</content>
</entry>
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