Skip to content

[SYCL][Doc] Update SPV_INTEL_function_pointers spec #17857

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
KornevNikita merged 4 commits into from
Feb 13, 2026
Merged

[SYCL][Doc] Update SPV_INTEL_function_pointers spec #17857

Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
192d99d
[SYCL][Doc] Update SPV_INTEL_function_pointers spec
AlexeySachkov Apr 4, 2025
a236575
Merge remote-tracking branch 'origin/sycl' into private/asachkov/upda…
KornevNikita Feb 12, 2026
248a5ee
Uplift to 1.6.6
KornevNikita Feb 12, 2026
7ba7577
Add add an issue
KornevNikita Feb 13, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
226 changes: 88 additions & 138 deletions sycl/doc/design/spirv-extensions/SPV_INTEL_function_pointers.asciidoc
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,3 +1,11 @@
:OpConstantFunctionPointerINTEL_token: 5600
:OpFunctionPointerCallINTEL_token: 5601
:ReferencedIndirectlyINTEL_token: 5602
:FunctionPointersINTEL_token: 5603
:IndirectReferencesINTEL_token: 5604
:CodeSectionINTEL_token: 5605
:ArgumentAttributeINTEL_token: 6409

= SPV_INTEL_function_pointers

== Name Strings
Expand All @@ -24,7 +32,7 @@ https://github.com/intel/llvm/issues

== Notice

Copyright (c) 2019 Intel Corporation. All rights reserved.
Copyright (c) 2019-2023 Intel Corporation. All rights reserved.

== Status

Expand All @@ -40,34 +48,33 @@ If you are interested in using this feature in your software product, please let

[width="40%",cols="25,25"]
|==================================
| Last Modified Date | 2025-03-13
| Revision | 10
| Last Modified Date | 2026-02-12
| Revision | 12
|==================================

== Dependencies

This extension is written against the SPIR-V Specification, Version 1.6
Revision 5, Unified.
Revision 6, Unified.

This extension interacts with link:https://github.khronos.org/SPIRV-Registry/extensions/KHR/SPV_KHR_untyped_pointers.html[*SPV_KHR_untyped_pointers*] extension.

This extension requires SPIR-V 1.0.

== Overview

The goal of this extension is to allow translation of function pointers into
The goal of this extension is to allow representation of function pointers in
SPIR-V.

This extensions brings two "levels" of function pointers support added under
corresponding capabilities:
This is done by adding two new instructions: one which correspond to
"address of" operator and another which allows to perform an indirect call.
They both are added under *FunctionPointersINTEL* capability.

- Two new instructions added to support "address of" operator and indirect
function call under *FunctionPointersINTEL* capability
On top of that, a couple more things are being added by the extension:
- One new decoration added under *IndirectReferencesINTEL* to support functions
which are not referenced directly in the module. The idea is to extract
pointer to a function from the module and pass it as argument into one of
entry points where it will be used.
See *cl_intel_function_pointers* extension specification for more details.
- One new decoration added under *FunctionPointersINTEL* to preserve argument
attributes of *OpFunctionPointerCall*.

Expand All @@ -80,83 +87,15 @@ must be present in the module:
OpExtension "SPV_INTEL_function_pointers"
----

== New Capabilities

This extension introduces new capabilities:

----
FunctionPointersINTEL
IndirectReferencesINTEL
----

== New Instructions

Instructions added under the *FunctionPointersINTEL* capability:

----
OpConstantFunctionPointerINTEL
OpFunctionPointerCallINTEL
----

== New Decorations

Decorations added under the *IndirectReferencesINTEL* capability:

----
ReferencedIndirectlyINTEL
----

Decorations added under the *FunctionPointersINTEL* capability:

----
ArgumentAttributeINTEL
----

== New Storage Classes

Storage Classes added under the *FunctionPointersINTEL* capability:

----
CodeSectionINTEL
----


== Token Number Assignments

[width="40%"]
[cols="70%,30%"]
[grid="rows"]
|====
|OpConstantFunctionPointerINTEL | 5600
|OpFunctionPointerCallINTEL | 5601
|ReferencedIndirectlyINTEL | 5602
|FunctionPointersINTEL | 5603
|IndirectReferencesINTEL | 5604
|CodeSectionINTEL | 5605
|ArgumentAttributeINTEL | 6409
|====

== Modifications to the SPIR-V Specification, Version 1.6

=== Terms

[red]*TODO* Should we update _Opaque Type_ definition with function pointers
which points to functions taking Opaque types as arguments or returning them?

Modify Section 2.2.2, Types, add the following at the end of the section: ::

[[FunctionPointer]]'Function Pointer': A pointer that results from the following
instruction:

- *OpConstantFunctionPointerINTEL*

Additionally, any *OpSelect*, *OpPhi*, *OpFunctionCall*, *OpPtrAccessChain*,
*OpLoad*, *OpAccessChain*, *OpInBoundAccessChain*, or *OpCopyObject* thas takes
a function pointer as an operand also produces a function pointer. An
*OpFunctionParameter* of pointer type is function pointer if any
*OpFunctionCall* to the function statically passes a function pointer as the
value of the parameter. *OpCompositeExtract* and *OpConstantNull* return
function pointer if 'Result type' is function pointer.
[[FunctionPointer]]'Function Pointer': A pointer that points to a function, i.e.
a value of *OpTypePointer* whose _Type_ argument is an id of an
*OpTypeFunction*.

Modify Section 2.9, Function Calling, add the following after the first sentence: ::

Expand All @@ -167,57 +106,83 @@ the arguments to pass. All arguments are passed by value into the called
function. This includes pointers, through which a callee object could be
modified.

=== Validation Rules

Modify section 2.16.1, Universal Validation Rules by adding new rules: ::

- It is illegal to use <<FunctionPointer, Function Pointer>> as 'Pointer' argument
of *OpLoad* and *OpStore* instructions.

- It is illegal to use <<FunctionPointer, Function Pointer>> as 'Pointer' and
'Source' arguments of *OpCopyMemory*, *OpCopyMemorySized* instructions.

=== Storage Classes

Modify Section 3.7, Storage Class, adding to the end of the list of storage classes: ::
Modify Section 3.2.6, Storage Class, adding to the end of the list of storage classes: ::

[cols="1,4,4",options="header",width="100%"]
|====
2+| Storage Class| <<Capability,Enabling Capabilities>> |
5605 | *CodeSectionINTEL* +
{CodeSectionINTEL_token} | *CodeSectionINTEL* +
This storage represents function pointers. Visible across all functions of
all invocations of all work groups.
| *FunctionPointersINTEL*
|====

Modify Section 3.2.6, Storage Class, modifying description of *Generic* Storage Class: ::

[cols="1,4,4",options="header",width="100%"]
|====
2+| Storage Class| <<Capability,Enabling Capabilities>> |
8 | *Generic* +
For generic pointers, which overload the *Function*, *Workgroup*,
*CrossWorkgroup* and *CodeSectionINTEL* Storage Classes.
| *GenericPointer*
|====

=== Decorations

Modify Section 3.20, Decoration, adding to the end of the list of decorations: ::
Modify Section 3.2.19, Decoration, adding to the end of the list of decorations: ::

[cols="1,6,1,1,6",options="header",width = "100%"]
[cols="1,6,1,1,6",options="header",width="100%"]
|====
2+^.^| Decoration 2+<.^| Extra Operands
| <<Capability,Enabling Capabilities>> |
5602 | *ReferencedIndirectlyINTEL* +
This mark means that function might not have direct uses within the module,
but it's address can be obtained and passed into an Entry Point for further
usage via *OpFunctionPointerCallINTEL*. This function must not be optimized
{ReferencedIndirectlyINTEL_token} | *ReferencedIndirectlyINTEL* +
Indicates that a function might not have direct uses within the module,
but its address can be obtained and passed into an Entry Point and called
using *OpFunctionPointerCallINTEL*. This function must not be optimized
out based on call graph/reachability analysis 2+||
*IndirectReferencesINTEL*|
6409 | *ArgumentAttributeINTEL* +
Indicates an attribute of argument of an indirect function call. Apply to an *OpFunctionPointerCallINTEL*. +
_Index_ is an unsigned 32-bit integer indicating the argument number _N_. The attribute is applied to _Argument N_ of *OpFunctionPointerCallINTEL*. _Argument Attribute_ specifies which attribute is applied, its possible values are enumerated in section "Function Parameter Attribute" of the core SPIR-V specification.
2+|
{ArgumentAttributeINTEL_token} | *ArgumentAttributeINTEL* +
Indicates an attribute of argument of an indirect function call. Apply to an
*OpFunctionPointerCallINTEL*. +
_Index_ is an unsigned 32-bit integer indicating the argument number _N_.
The attribute is applied to _Argument N_ of *OpFunctionPointerCallINTEL*.
_Argument Attribute_ specifies which attribute is applied, it should be a value
which is valid to be used with *FuncParamAttr* Decoration.
|
_<<Literal, Literal>> +
Index +
<<Argument Attribute, Argument Attribute>> +
Index_
|
_<<Argument Attribute, Argument Attribute>> +
Argument Attribute_ |
*FunctionPointersINTEL*|
|====

=== Capabilities

Modify Section 3.31, Capability, adding to the end of the list of capabilities: ::
Modify Section 3.2.30, Capability, adding to the end of the list of capabilities: ::


[cols="1,10,8,8",options="header",width = "80%"]
[cols="1,10,8,8",options="header",width="80%"]
|====
2+^.^| Capability | Implicitly Declares | Enabled by Extension

| 5603
| {FunctionPointersINTEL_token}
| *FunctionPointersINTEL*
| *Addresses* | *SPV_INTEL_function_pointers*
| 5604
| {IndirectReferencesINTEL_token}
| *IndirectReferencesINTEL*
| *Addresses* | *SPV_INTEL_function_pointers*

Expand All @@ -226,13 +191,7 @@ Modify Section 3.31, Capability, adding to the end of the list of capabilities:

=== Instructions

Modify Section 3.56.6, Type-Declaration Instructions, change the third sentence in the description of *OpTypeFunction* instruction to say: ::

*OpTypeFunction* can be used as operand of *OpTypePointer* to declare function
pointer type. *OpFunction* and *OpTypePointer* are only valid uses of
*OpTypeFunction*.

Modify Section 3.56.7, Constant-Creation Instructions, adding to the end of the list of instructions: ::
Modify Section 3.3.7, Constant-Creation Instructions, adding to the end of the list of instructions: ::

[cols="2*1,3*3",width="100%"]
|=====
Expand All @@ -249,10 +208,10 @@ _Result Type_ must be a link:https://github.khronos.org/SPIRV-Registry/extension
operand. Its _Storage Class_ operand must be *CodeSectionINTEL*
| <<Capability,Capability>>: +
*FunctionPointersINTEL*
| 4 | 5600 | '<id>' 'Result Type' | '<id> Result ' | '<id>' 'Function'
| 4 | {OpConstantFunctionPointerINTEL_token} | '<id>' 'Result Type' | '<id> Result ' | '<id>' 'Function'
|=====

Modify Section 3.56.9, Function Instructions, adding to the end of the list of instructions: ::
Modify Section 3.3.9, Function Instructions, adding to the end of the list of instructions: ::

[cols="2*1,4*3",width="100%"]
|=====
Expand All @@ -271,40 +230,12 @@ was used as _Type_ operand of _Function Pointer_ argument and the calling
argument types must match the formal parameter types.
| <<Capability,Capability>>: +
*FunctionPointersINTEL*
| 4 + variable | 5601
| 4 + variable | {OpFunctionPointerCallINTEL_token}
| '<id>' 'Result Type' | <<ResultId,'Result <id>' >> | '<id>' +
'Function Pointer' |
'<id>, <id>, ..., <id>' 'Argument 0', 'Argument 1', ..., 'Argument N'
|=====

== Validation Rules

It is legal to use <<FunctionPointer, Function Pointer>> as 'Result Type' of
*OpFunctionArgument*, *OpCompositeExtract*, *OpUndef* and *OpConstantNULL*.

It is legal to use <<FunctionPointer, Function Pointer>> as 'Return Type' of
*OpTypeFunction*.

It is legal to use <<FunctionPointer, Function Pointer>> as 'Pointer'
argument of *OpConvertPtrToU* and as 'Result Type' of *OpConvertUToPtr*.

It is legal to use <<FunctionPointer, Function Pointer>> as 'Object'
argument of *OpCompositeInsert*.

It is illegal to use <<FunctionPointer, Function Pointer>> as 'Pointer'
argument of *OpPtrCastToGeneric*.

It is illegal to use <<FunctionPointer, Function Pointer>> as 'Pointer' argument
of *OpLoad* and *OpStore* instructions.

It is illegal to use <<FunctionPointer, Function Pointer>> as 'Pointer' and
'Source' arguments of *OpCopyMemory*, *OpCopyMemorySized* instructions.

It is legal to compare <<FunctionPointer, Function Pointers>> between each other
using *OpPtrEqual* or *OpPtrNotEqual*. However, it is illegal to use
<<FunctionPointer, Function Pointer>> as any argument of *OpPtrDiff*
instruction.

== Issues

. It is unclear which <<Storage_Class,Storage Class>> should function pointers
Expand Down Expand Up @@ -360,6 +291,22 @@ in *OpConstantComposite*, but how should we specify that in this spec?
Removed *OpFunctionPointerINTEL* instruction.
--

. Consider unification of the extension according to a
link:https://github.com/intel/llvm/pull/17857#issuecomment-2984465908[comment]
from Hugobros3:
+
"Our main requirements over the Intel version is to have a notion of tail-calls,
or alternatively calls to non-re-entrant functions (such that no stack is
required to support the execution), and to gate regular (stackful) calls behind
a capability.
+
We also wanted to gate in-module and inter-modules calls between different
capabilities."
+
--
*UNRESOLVED*
--

//. Issue.
//+
//--
Expand Down Expand Up @@ -391,5 +338,8 @@ pointers. Updated validation rules. Misc updates.
|8|2021-11-15|Nikita Kornev|Added new *ArgumentAttributeINTEL* decoration.
|9|2022-10-08|Dmitry Sidorov, Alex Bezzubikov, Alexey Sachkov|Replaced *OpFunctionPointerINTEL* with
*OpConstantFunctionPointerINTEL*
|10|2025-03-13|Viktoria Maximova|Allow to use *OpTypeUntypedPointerKHR* as a result type of *OpConstantFunctionPointerINTEL*.
|10|2022-12-13|Alexey Sachkov|Uplift to SPIR-V 1.6 spec, refactor validation +
rules section, remove listing of new instructions at the beginning
|11|2025-03-13|Viktoria Maximova|Allow to use *OpTypeUntypedPointerKHR* as a result type of *OpConstantFunctionPointerINTEL*.
|12|2026-02-12|Nikita Kornev| Uplift to SPIR-V 1.6, Revision 6.
|========================================