Move the bulk of the constant evaulation logic out of transform::FoldConstants and into Resolver and sem::Expression.
transform::FoldConstants now replace TypeConstructor nodes that have a constant value on the expression.
This is ground work to:
* Cleaning up the HLSL uniform buffer indexing, which is `/` and `%` arithmatic heavy
* Prepares us to handle `constexpr` when it lands in the spec
* Provide a centralized place to do constant evaluation, instead of the
having similar logic scattered around the codebase.
Change-Id: I3e2f542be692046a8d243b62a82556db519953e7
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/57426
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: James Price <jrprice@google.com>
This reverts commit fd5829e5ea.
Reason for revert: Temporarily reverting as this is preventing a tint->dawn roll, which is needed to fix the dawn->chrome roll.
Original change's description:
> Validate storage class constraints
>
> As defined by https://gpuweb.github.io/gpuweb/wgsl/#storage-class-layout-constraints
>
> Bug: tint:643
> Change-Id: I9c78ba69a792a80c263a17b0a6e9b4810fdb7f30
> Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/56780
> Kokoro: Kokoro <noreply+kokoro@google.com>
> Commit-Queue: Antonio Maiorano <amaiorano@google.com>
> Reviewed-by: Ben Clayton <bclayton@google.com>
TBR=bclayton@google.com,amaiorano@google.com,noreply+kokoro@google.com,tint-scoped@luci-project-accounts.iam.gserviceaccount.com
Change-Id: I8dbd0e46b3e3291ef08797a196d0d9abd2a78845
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: tint:643
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/57704
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Ben Clayton <bclayton@google.com>
Transforms a for-loop into a loop.
Will be required by the SPIR-V writer.
Bug: tint:952
Change-Id: Iba859bd144d702cee85374f2cfcb94cd7465ca98
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/57202
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
Runs the statement(s) at the end of the lexical scope
Change-Id: I74de02b7204b56016c7bbe71fee4ece498d3570d
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51923
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
And add `vec` and `mat` to the reserved keyword list (see https://github.com/gpuweb/gpuweb/pull/1896)
Move these reserved keyword checks out of the lexer and into the parser.
Generate a sensible error message.
Add tests.
Change-Id: I1876448201a2fd773f38f337b4e49bc61a7642f7
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/56545
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
A Transform that attempts to convert WGSL `loop {}` statements into a for-loop statement.
For-loops cause less broken behavior with FXC than our current loop constructs.
Bug: tint:952
Change-Id: I0b7b1dbec9df4c004b0419d3feae53a195ec79bb
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/56767
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
This transform is intended to clean up the output of the SPIR-V reader, so that we can pattern match loops that can be transformed into a for-loop.
Bug: tint:952
Change-Id: Iba58e4e1f6e20daaf7715e493df53346cdb7c89f
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/56766
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
Commit-Queue: David Neto <dneto@google.com>
Auto-Submit: Ben Clayton <bclayton@google.com>
We will want this transform to do more bounds and argument sanitization.
Bug: tint:748
Change-Id: I38cb9623622e9f5ab85d8cd420d669ca6be77099
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/56543
Auto-Submit: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Common logic between the HLSL, WGSL and MSL writers has been moved into
the TextGenerator base class.
Fixed: tint:892
Change-Id: I0f469516947fe64817ce6251e436da74e5e176e8
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/56068
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Reviewed-by: James Price <jrprice@google.com>
Generate a uniform buffer that will receive the lengths of all storage
buffers, and use this to implement calls to arrayLength(). The
transform is provided with a set of mappings from storage buffer
binding points to the corresponding index into the array of buffer
lengths. The transform reports whether it generated the uniform
buffers or not.
Use this transform from the MSL sanitizer, using the binding number as
the index into the array. This matches the behavior of spirv-cross,
and so works with how Dawn already produces this uniform buffer.
Bug: tint:256
Change-Id: I2682d2d024e8daa30f78270b8cfb6bbb32632133
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54480
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Zero initializes all referenced workgroup storage classed variables used by each entry point.
Bug: tint:280
Fixed: tint:911
Change-Id: I3fca26a10f015f08fedef404720bbe6fd7b343a9
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/55243
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
Reviewed-by: James Price <jrprice@google.com>
Instead of a ConstantBuffer.
HLSL requires that each structure field in a UBO is 16 byte aligned.
WGSL has much looser constraints with its UBO field alignment rules.
Instead generate an array of uint4 vectors, and index into this, much
like we index into [RW]ByteAddressBuffers for SSBOs.
Extend the DecomposeStorageAccess transform to support uniforms too.
This has been renamed to DecomposeMemoryAccess.
Change-Id: I3868ff80af1ab3b3dddfbf5b969724cb87ef0744
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/55246
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
Dynamic indexes are limited to references to matrices and arrays
https://github.com/gpuweb/gpuweb/pull/1801
Bug: tint:867
Change-Id: I114daa053c8a4ffd23ce784ac4538567a551cc21
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54701
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Auto-Submit: Sarah Mashayekhi <sarahmashay@google.com>
Replaces arrays with an explicit stride with an array to a structure holding the element padded with a `[[size]]` decoration.
Note that the HLSL writer is still not correctly emitting structure fields with a `[[size]]`, which will be fixed in a follow up change.
Bug: tint:182
Bug: tint:895
Fixed: tint:180
Fixed: tint:649
Change-Id: Ic135dfc89309ac805507e9f39392577c7f82d154
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54582
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
Reviewed-by: James Price <jrprice@google.com>
These have been deprecated, and their usages in Dawn, CTS and samples have been updated.
Fixed: tint:846
Change-Id: I74b831fd5be2e7ca02e8208835eac8beddcef9af
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54325
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
Reviewed-by: James Price <jrprice@google.com>
And replace the MSL writer's logic to do this with the transform.
We need to do the same thing in HLSL, and in the future GLSL too.
Partially reverts fbfde720
Change-Id: Ie280e011bc3ded8e15ccacc0aeb12da3c2407389
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54242
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
And fix issues where global variables would not be emitted unless they were transitively referenced by an entry point.
This change requires crbug.com/tint/697 to be fixed before landing.
Change-Id: I712bd9d369e08c9a3cdfb0f114c3609584f91f28
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54241
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
We have the end-to-end test-runner which validates all this stuff.
There's no need to also Validate in the unit tests.
Change-Id: I8fbc1ecd395efcedec4aa41085e691c88f3b66a5
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54160
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: James Price <jrprice@google.com>
Also split out validation tests from call_test.cc into call_validation_test.cc.
Bug: tint:886
Change-Id: I1e1dee9b7c348363e89080cdecd3119cc004658f
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54063
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
- Add resolver/call_test.cc for new unit tests, and move a couple that
were in resolver/validation_test.cc to it
- Fix CalculateArrayLength transform so that it passes the address of
the u32 it creates to the internal function
- Fix tests broken as a result of this change
Bug: tint:664
Change-Id: If713f9828790cd51224d2392d42c01c0057cb652
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/53920
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Handle access control on var declarations instead of via [[access]]
decorations. This change does the minimal work to migrate the WGSL
parser over to the new syntax. Additional changes will be needed
to correctly generate defaulted access qualifiers, as well as
validating access usage.
The [[access]] decorations are still supported by the WGSL parser,
with new deprecated warnings, but not for aliases. Example:
var x : [[access(x)]] alias_to_struct;
Making this work is far more effort than I want to dedicate to backwards
compatibility, and I do not beleive any real-world usage will be doing
this.
Still TODO:
* Adding access control as the optional, third parameter to ptr<>.
* Calculating default accesses for the various storage types.
* Validating usage of variables against the different accesses.
Bug: tint:846
Change-Id: If8ca82e5d16ec319ecd01f9a2cafffd930963bde
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/53088
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: James Price <jrprice@google.com>
Reviewed-by: David Neto <dneto@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Use the new [[stage()]] decorations in intrinsics.def to validate that intrinsics are only called from the correct pipeline stages.
Fixed: tint:657
Change-Id: I9efda26369c45c6f816bdaa53408d3909db403a1
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/53084
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: David Neto <dneto@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Performs output validation with spirv-val for SPIR-V (as before), HLSL
validation with DXC, and MSL validation with the Metal Shader Compiler.
Disable HLSL tests that fail to validate
Bug: tint:812
Change-Id: If78c351b4e23c7fb50d333eacf9ee7cc81d18564
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51280
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Pull the HLSL transformation out to a standalone transform that can be
used by both HLSL and MSL.
The new E2E tests do not yet pass for MSL because they produce array
assignments, which will be addressed in the next patch.
Fixed: tint:826
Change-Id: Idc27c81ad45e3d4ab96d82663927d2fc1384618e
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/52842
Auto-Submit: James Price <jrprice@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Signed zeros are emitted.
Subormal numbers are emitted as hex float.
Handling Inf and NaN is unresolved in the spec.
See https://github.com/gpuweb/gpuweb/issues/1769
NaN tests are disabled, due to platform dependence.
Windows x86-64 seems to always set the high mantissa bit
on NaNs.
Fixed: tint:76
Change-Id: I06c69b93b04c869a63ec2f574022996acc7a6dbe
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/52321
Commit-Queue: David Neto <dneto@google.com>
Auto-Submit: David Neto <dneto@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Performs basic peephole optimizations on the AST.
Use in transform::Hlsl.
Required to have the DecomposeStorageAccess transform operate correctly with the output of InlinePointerLets transform, specifically when declaring `let` pointer expressions to storage buffers.
Fixed: tint:221
Fixed: tint:492
Fixed: tint:829
Change-Id: I536390921a6492378104e9c3c100d9e761294a27
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51921
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Reviewed-by: David Neto <dneto@google.com>
BlockStatement for the root block of a function
Add some basic tests for this lot.
Bug: tint:812
Change-Id: I26b65717798cbff576a44bd78fbcb5c8f0d013e6
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51368
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Alastair Donaldson <allydonaldson@googlemail.com>
Use this as part of the Spirv sanitizer.
Cleans up buggy dynamic array indexing logic in the SPIR-V writer.
Fixed: tint:824
Change-Id: Ia408e49bd808bc8dbf3a1897eb47f9b33b71fdfb
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51780
Commit-Queue: Ben Clayton <bclayton@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Auto-Submit: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Add `transform::InlinePointerLets` - a Transform that moves all usage of function-scope `let` statements of a pointer type into their places of usage.
Make the HLSL writer transform pointer parameters to `inout`.
Fixed: tint:183
Change-Id: I0a7552fa6cd31c7b7691e64feae3170a81cc6c49
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51281
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: David Neto <dneto@google.com>
A helper class and macro used to simplify scope-based assignment of
variables.
Change-Id: I02b3a05240a2c4628f813de931c40d8fba3cb07b
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51480
Auto-Submit: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
This reverts commit 594075a2f0.
Reason for revert: This is not a complete solution. It does not cover assignment of variables of the same struct type, but of different access types. For example:
```
[[block]] struct S{ i : 32; };
var<storage> gr : [[access(read)]] S;
var<storage> gw : [[access(write)]] S;
fn f() {
var a : S;
a = gr;
gw = a;
}
```
With my CL, we currently generate invalid assignments because the new types of 'S' for 'gr' and 'gw' are now all different types. We would need to generate functions to assign between them.
In the end, we will drop this strategy, and instead, Dawn will be modified to not rely on names.
Original change's description:
> Add DuplicateStorageStruct transform
>
> This transform is currently required by Dawn for it's GLSL backend so
> that SPIRV-Cross does not end up renaming the structures internally,
> which it does to fix aliasing problems. We can remove this transform
> if/once Dawn using binding numbers rather than names for uniform/storage
> buffer data.
>
> Bug: tint:386
> Bug: tint:808
>
> CloneContext: allow insert before/after of a node marked for removal
> Change-Id: I3ff3b37bca62db07d5c759250dd4777e279b7a4f
> Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51403
> Commit-Queue: Ben Clayton <bclayton@google.com>
> Kokoro: Kokoro <noreply+kokoro@google.com>
> Reviewed-by: Ben Clayton <bclayton@google.com>
TBR=bclayton@google.com,amaiorano@google.com,noreply+kokoro@google.com
Change-Id: I695347b0ffe8be23b9dc44885af378be56512406
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: tint:386
Bug: tint:808
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51500
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
This transform is currently required by Dawn for it's GLSL backend so
that SPIRV-Cross does not end up renaming the structures internally,
which it does to fix aliasing problems. We can remove this transform
if/once Dawn using binding numbers rather than names for uniform/storage
buffer data.
Bug: tint:386
Bug: tint:808
CloneContext: allow insert before/after of a node marked for removal
Change-Id: I3ff3b37bca62db07d5c759250dd4777e279b7a4f
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51403
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
This change implements pointers and references as described by the WGSL
specification change in https://github.com/gpuweb/gpuweb/pull/1569.
reader/spirv:
* Now emits address-of `&expr` and indirection `*expr` operators as
needed.
* As an identifier may now resolve to a pointer or reference type
depending on whether the declaration is a `var`, `let` or
parameter, `Function::identifier_values_` has been changed from
an ID set to an ID -> Type* map.
resolver:
* Now correctly resolves all expressions to either a value type,
reference type or pointer type.
* Validates pointer / reference rules on assignment, `var` and `let`
construction, and usage.
* Handles the address-of and indirection operators.
* No longer does any implicit loads of pointer types.
* Storage class validation is still TODO (crbug.com/tint/809)
writer/spirv:
* Correctly handles variables and expressions of pointer and
reference types, emitting OpLoads where necessary.
test:
* Lots of new test cases
Fixed: tint:727
Change-Id: I77d3281590e35e5a3122f5b74cdeb71a6fe51f74
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/50740
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
In preparation for implementing
https://github.com/gpuweb/gpuweb/issues/1604, this change removes the
sem::AccessControl node. Instead, the ast::AccessControl::Access enum is
now on the sem::StorageTexture class, as well as on sem::Variable. For
sem::Variable, the field is set when the variable's type is either a
storage buffer or a storage texture.
Bug: tint:802
Change-Id: Id479af36b401d067b015027923f4e715f5f69f25
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51020
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Keep track of any constant IDs specified in the shader, and then
allocate IDs for the remaining constants when creating the semantic
info.
Bug: tint:755
Change-Id: I6a76b1193cac459b62582cde7469b092dde51d5d
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/50841
Commit-Queue: James Price <jrprice@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Auto-Submit: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
This has been moved into the Spirv sanitizer, and Dawn is now using
this path.
Change-Id: Iffcbbc1c84e6bad0ebc51ded82d998bb307e2d6d
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/50564
Auto-Submit: James Price <jrprice@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
With the parsers now using ast::Types, nothing should be producing these any more.
This change also removes Resolver::Canonical(), which is now unneeded as there are no sem::Aliases to remove.
Bug: tint:724
Change-Id: I0c1a49f49372c1fcc37864502f07c5c76328d471
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/50304
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: James Price <jrprice@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Don't create disjoint AST type nodes.
Instead use a new bespoke type hierarchy that can Build() the required
AST nodes.
Change-Id: I523f97054de2c553095056c0bafc17c48064cf53
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/49966
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
There's now no need to have both.
Removes a whole bunch of Sem().Get() smell, and simplifies the resolver.
Also fixes a long-standing issue where an array with an explicit, but equal-to-implicit-stride attribute would result in a different type to an array without the decoration.
Bug: tint:724
Fixed: tint:782
Change-Id: I0202459009cd45be427cdb621993a5a3b07ff51e
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/50301
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
There's now no need to have both.
Removes a whole bunch of Sem().Get() smell, and simplifies the resolver.
Bug: tint:724
Fixed: tint:761
Change-Id: I756a32680ac52441fd6eebf6fc53dd507ef5e538
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/49961
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Ben Clayton
Antonio Maiorano
James Price
Sarah
David Neto