[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-13 Thread Joseph Huber via cfe-commits 

https://github.com/jhuber6 closed 
https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-13 Thread Shilei Tian via cfe-commits 

https://github.com/shiltian approved this pull request.

LG

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Joseph Huber via cfe-commits 

jhuber6 wrote:

> Add to release notes?

Done

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Joseph Huber via cfe-commits 

https://github.com/jhuber6 updated 
https://github.com/llvm/llvm-project/pull/81331

>From 4a0ee4be9690e0665ca93d63ffdd2dea404fd72d Mon Sep 17 00:00:00 2001
From: Joseph Huber 
Date: Fri, 9 Feb 2024 16:13:42 -0600
Subject: [PATCH] [LLVM] Add `__builtin_readsteadycounter` intrinsic and
 buiiltin

Summary:
This patch adds a new intrinsic and builtin function mirroring the
existing `__builtin_readcyclecounter`. The difference is that this
implementation targets a separate counter that some targets have which
returns a fixed frequency clock that can be used to determine elapsed
time, this is different compared to the cycle counter which often has
variable frequency. This is currently only valid for the NVPTX and
AMDGPU targets.
---
 clang/docs/LanguageExtensions.rst | 33 ++
 clang/docs/ReleaseNotes.rst   |  3 +
 clang/include/clang/Basic/Builtins.td |  6 ++
 clang/lib/CodeGen/CGBuiltin.cpp   |  4 ++
 clang/test/CodeGen/builtins.c |  6 ++
 llvm/include/llvm/CodeGen/ISDOpcodes.h|  6 ++
 llvm/include/llvm/IR/Intrinsics.td|  2 +
 llvm/include/llvm/Support/TargetOpcodes.def   |  3 +
 llvm/include/llvm/Target/GenericOpcodes.td|  6 ++
 .../Target/GlobalISel/SelectionDAGCompat.td   |  1 +
 .../include/llvm/Target/TargetSelectionDAG.td |  3 +
 llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp  |  2 +
 llvm/lib/CodeGen/IntrinsicLowering.cpp|  6 ++
 llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp |  6 +-
 .../SelectionDAG/LegalizeIntegerTypes.cpp |  7 ++-
 llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h |  2 +-
 .../SelectionDAG/SelectionDAGBuilder.cpp  |  8 +++
 .../SelectionDAG/SelectionDAGDumper.cpp   |  1 +
 llvm/lib/CodeGen/TargetLoweringBase.cpp   |  3 +
 .../lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp |  2 +
 .../Target/AMDGPU/AMDGPURegisterBankInfo.cpp  |  1 +
 llvm/lib/Target/AMDGPU/SIISelLowering.cpp |  4 ++
 llvm/lib/Target/AMDGPU/SMInstructions.td  | 14 +
 llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp   |  2 +
 llvm/lib/Target/NVPTX/NVPTXInstrInfo.td   |  1 -
 llvm/lib/Target/NVPTX/NVPTXIntrinsics.td  |  1 +
 .../GlobalISel/legalizer-info-validation.mir  |  3 +
 llvm/test/CodeGen/AMDGPU/readsteadycounter.ll | 24 +++
 llvm/test/CodeGen/NVPTX/intrinsics.ll | 12 
 .../builtins/match-table-replacerreg.td   | 24 +++
 .../match-table-imms.td   | 32 +-
 .../match-table-intrinsics.td |  5 +-
 .../match-table-patfrag-root.td   |  4 +-
 .../GlobalISelCombinerEmitter/match-table.td  | 62 +--
 llvm/test/TableGen/GlobalISelEmitter.td   |  2 +-
 35 files changed, 229 insertions(+), 72 deletions(-)
 create mode 100644 llvm/test/CodeGen/AMDGPU/readsteadycounter.ll

diff --git a/clang/docs/LanguageExtensions.rst 
b/clang/docs/LanguageExtensions.rst
index e91156837290f7..ca78a5c39cf736 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -2764,6 +2764,39 @@ Query for this feature with 
``__has_builtin(__builtin_readcyclecounter)``. Note
 that even if present, its use may depend on run-time privilege or other OS
 controlled state.
 
+``__builtin_readsteadycounter``
+--
+
+``__builtin_readsteadycounter`` is used to access the fixed frequency counter
+register (or a similar steady-rate clock) on those targets that support it.
+The function is similar to ``__builtin_readcyclecounter`` above except that the
+frequency is fixed, making it suitable for measuring elapsed time.
+
+**Syntax**:
+
+.. code-block:: c++
+
+  __builtin_readsteadycounter()
+
+**Example of Use**:
+
+.. code-block:: c++
+
+  unsigned long long t0 = __builtin_readsteadycounter();
+  do_something();
+  unsigned long long t1 = __builtin_readsteadycounter();
+  unsigned long long secs_to_do_something = (t1 - t0) / tick_rate;
+
+**Description**:
+
+The ``__builtin_readsteadycounter()`` builtin returns the frequency counter 
value.
+When not supported by the target, the return value is always zero. This builtin
+takes no arguments and produces an unsigned long long result. The builtin does 
+not guarantee any particular frequency, only that it is stable. Knowledge of 
the 
+counter's true frequency will need to be provided by the user.
+
+Query for this feature with ``__has_builtin(__builtin_readsteadycounter)``.
+
 ``__builtin_dump_struct``
 -
 
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 402a2f8687386c..6633b544d93d32 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -117,6 +117,9 @@ C23 Feature Support
 Non-comprehensive list of changes in this release
 -
 
+- Added ``__builtin_readsteadycounter`` for reading fixed frequency hardware
+  counters.
+
 New Compiler Flags
 --
 
diff --git a/clang/include/clang/Basic/Builtins.td

[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Matt Arsenault via cfe-commits 

https://github.com/arsenm commented:

Add to release notes?

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Joseph Huber via cfe-commits 


@@ -104,6 +104,7 @@ std::string SDNode::getOperationName(const SelectionDAG *G) 
const {
   case ISD::ATOMIC_STORE:   return "AtomicStore";
   case ISD::PCMARKER:   return "PCMarker";
   case ISD::READCYCLECOUNTER:   return "ReadCycleCounter";
+  case ISD::READSTEADYCOUNTER: return "ReadFixedTimer";

jhuber6 wrote:

Forgot to fix that when I renamed it, thanks for spotting it.

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Joseph Huber via cfe-commits 


@@ -2764,6 +2764,37 @@ Query for this feature with 
``__has_builtin(__builtin_readcyclecounter)``. Note
 that even if present, its use may depend on run-time privilege or other OS
 controlled state.
 
+``__builtin_readsteadycounter``
+--
+
+``__builtin_readsteadycounter`` is used to access the fixed frequency counter
+register (or a similar steady-rate clock) on those targets that support it.
+The function is similar to ``__builtin_readcyclecounter`` above except that the
+frequency is fixed, making it suitable for measuring elapsed time.

jhuber6 wrote:

Good point, done.

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Joseph Huber via cfe-commits 

https://github.com/jhuber6 updated 
https://github.com/llvm/llvm-project/pull/81331

>From 50c0bacb8c33ff0c3caf5554bd198904839a2d2c Mon Sep 17 00:00:00 2001
From: Joseph Huber 
Date: Fri, 9 Feb 2024 16:13:42 -0600
Subject: [PATCH] [WIP][LLVM] Add `__builtin_readsteadycounter` intrinsic and
 buiiltin

Summary:
This patch adds a new intrinsic and builtin function mirroring the
existing `__builtin_readcyclecounter`. The difference is that this
implementation targets a separate counter that some targets have which
returns a fixed frequency clock that can be used to determine elapsed
time, this is different compared to the cycle counter which often has
variable frequency. This is currently only valid for the NVPTX and
AMDGPU targets.
---
 clang/docs/LanguageExtensions.rst | 33 ++
 clang/include/clang/Basic/Builtins.td |  6 ++
 clang/lib/CodeGen/CGBuiltin.cpp   |  4 ++
 clang/test/CodeGen/builtins.c |  6 ++
 llvm/include/llvm/CodeGen/ISDOpcodes.h|  6 ++
 llvm/include/llvm/IR/Intrinsics.td|  2 +
 llvm/include/llvm/Support/TargetOpcodes.def   |  3 +
 llvm/include/llvm/Target/GenericOpcodes.td|  6 ++
 .../Target/GlobalISel/SelectionDAGCompat.td   |  1 +
 .../include/llvm/Target/TargetSelectionDAG.td |  3 +
 llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp  |  2 +
 llvm/lib/CodeGen/IntrinsicLowering.cpp|  6 ++
 llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp |  6 +-
 .../SelectionDAG/LegalizeIntegerTypes.cpp |  7 ++-
 llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h |  2 +-
 .../SelectionDAG/SelectionDAGBuilder.cpp  |  8 +++
 .../SelectionDAG/SelectionDAGDumper.cpp   |  1 +
 llvm/lib/CodeGen/TargetLoweringBase.cpp   |  3 +
 .../lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp |  2 +
 .../Target/AMDGPU/AMDGPURegisterBankInfo.cpp  |  1 +
 llvm/lib/Target/AMDGPU/SIISelLowering.cpp |  4 ++
 llvm/lib/Target/AMDGPU/SMInstructions.td  | 14 +
 llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp   |  2 +
 llvm/lib/Target/NVPTX/NVPTXInstrInfo.td   |  1 -
 llvm/lib/Target/NVPTX/NVPTXIntrinsics.td  |  1 +
 .../GlobalISel/legalizer-info-validation.mir  |  3 +
 llvm/test/CodeGen/AMDGPU/readsteadycounter.ll | 24 +++
 llvm/test/CodeGen/NVPTX/intrinsics.ll | 12 
 .../builtins/match-table-replacerreg.td   | 24 +++
 .../match-table-imms.td   | 32 +-
 .../match-table-intrinsics.td |  5 +-
 .../match-table-patfrag-root.td   |  4 +-
 .../GlobalISelCombinerEmitter/match-table.td  | 62 +--
 llvm/test/TableGen/GlobalISelEmitter.td   |  2 +-
 34 files changed, 226 insertions(+), 72 deletions(-)
 create mode 100644 llvm/test/CodeGen/AMDGPU/readsteadycounter.ll

diff --git a/clang/docs/LanguageExtensions.rst 
b/clang/docs/LanguageExtensions.rst
index e91156837290f7..ca78a5c39cf736 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -2764,6 +2764,39 @@ Query for this feature with 
``__has_builtin(__builtin_readcyclecounter)``. Note
 that even if present, its use may depend on run-time privilege or other OS
 controlled state.
 
+``__builtin_readsteadycounter``
+--
+
+``__builtin_readsteadycounter`` is used to access the fixed frequency counter
+register (or a similar steady-rate clock) on those targets that support it.
+The function is similar to ``__builtin_readcyclecounter`` above except that the
+frequency is fixed, making it suitable for measuring elapsed time.
+
+**Syntax**:
+
+.. code-block:: c++
+
+  __builtin_readsteadycounter()
+
+**Example of Use**:
+
+.. code-block:: c++
+
+  unsigned long long t0 = __builtin_readsteadycounter();
+  do_something();
+  unsigned long long t1 = __builtin_readsteadycounter();
+  unsigned long long secs_to_do_something = (t1 - t0) / tick_rate;
+
+**Description**:
+
+The ``__builtin_readsteadycounter()`` builtin returns the frequency counter 
value.
+When not supported by the target, the return value is always zero. This builtin
+takes no arguments and produces an unsigned long long result. The builtin does 
+not guarantee any particular frequency, only that it is stable. Knowledge of 
the 
+counter's true frequency will need to be provided by the user.
+
+Query for this feature with ``__has_builtin(__builtin_readsteadycounter)``.
+
 ``__builtin_dump_struct``
 -
 
diff --git a/clang/include/clang/Basic/Builtins.td 
b/clang/include/clang/Basic/Builtins.td
index 31a2bdeb2d3e5e..193d5851f9f29f 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -1110,6 +1110,12 @@ def ReadCycleCounter : Builtin {
   let Prototype = "unsigned long long int()";
 }
 
+def ReadSteadyCounter : Builtin {
+  let Spellings = ["__builtin_readsteadycounter"];
+  let Attributes = [NoThrow];
+  let Prototype = "unsigned long long int()";
+}
+
 def Trap : Builtin {
   let Spellings = ["__builtin_trap"];

[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Artem Belevich via cfe-commits 


@@ -104,6 +104,7 @@ std::string SDNode::getOperationName(const SelectionDAG *G) 
const {
   case ISD::ATOMIC_STORE:   return "AtomicStore";
   case ISD::PCMARKER:   return "PCMarker";
   case ISD::READCYCLECOUNTER:   return "ReadCycleCounter";
+  case ISD::READSTEADYCOUNTER: return "ReadFixedTimer";

Artem-B wrote:

Should it be "ReadSteadyCounter" ? 

Also, whitespace/alignment looks off.

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Artem Belevich via cfe-commits 


@@ -2764,6 +2764,37 @@ Query for this feature with 
``__has_builtin(__builtin_readcyclecounter)``. Note
 that even if present, its use may depend on run-time privilege or other OS
 controlled state.
 
+``__builtin_readsteadycounter``
+--
+
+``__builtin_readsteadycounter`` is used to access the fixed frequency counter
+register (or a similar steady-rate clock) on those targets that support it.
+The function is similar to ``__builtin_readcyclecounter`` above except that the
+frequency is fixed, making it suitable for measuring elapsed time.

Artem-B wrote:

Should we mention that we do not guarantee any particular frequency, just that 
it's stable and it's up to the user to figure out the actual frequency, if they 
need to.

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Artem Belevich via cfe-commits 

https://github.com/Artem-B commented:

LGTM with few nits for general and NVPTX parts.

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Artem Belevich via cfe-commits 

https://github.com/Artem-B edited 
https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Joseph Huber via cfe-commits 

jhuber6 wrote:

> New intrinsic sounds right - a constant frequency counter is a different 
> thing to a variable frequency counter.
> 
> "Steady" implies unchanging, so I'd agree with `readfixedfreqtimer` or 
> similar.

I think `steady` has sufficient context here, (i.e. 
https://en.cppreference.com/w/cpp/chrono/steady_clock). And I mostly like it 
because it reads very similar to the existing `readcyclecounter`.

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Jon Chesterfield via cfe-commits 

JonChesterfield wrote:

New intrinsic sounds right - a constant frequency counter is a different thing 
to a variable frequency counter.

"Steady" implies unchanging, so I'd agree with `readfixedfreqtimer` or similar.

We can't have a ratio between the two counters since one changes frequency and 
one doesn't.

Does x64 have something that maps usefully onto a fixed frequency counter 
intrinsic?

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Joseph Huber via cfe-commits 

https://github.com/jhuber6 updated 
https://github.com/llvm/llvm-project/pull/81331

>From 30341079e795c2668588b791f2c97b44006e7a04 Mon Sep 17 00:00:00 2001
From: Joseph Huber 
Date: Fri, 9 Feb 2024 16:13:42 -0600
Subject: [PATCH] [WIP][LLVM] Add `__builtin_readsteadycounter` intrinsic and
 buiiltin

Summary:
This patch adds a new intrinsic and builtin function mirroring the
existing `__builtin_readcyclecounter`. The difference is that this
implementation targets a separate counter that some targets have which
returns a fixed frequency clock that can be used to determine elapsed
time, this is different compared to the cycle counter which often has
variable frequency. This is currently only valid for the NVPTX and
AMDGPU targets.
---
 clang/docs/LanguageExtensions.rst | 31 ++
 clang/include/clang/Basic/Builtins.td |  6 ++
 clang/lib/CodeGen/CGBuiltin.cpp   |  4 ++
 clang/test/CodeGen/builtins.c |  6 ++
 llvm/include/llvm/CodeGen/ISDOpcodes.h|  6 ++
 llvm/include/llvm/IR/Intrinsics.td|  2 +
 llvm/include/llvm/Support/TargetOpcodes.def   |  3 +
 llvm/include/llvm/Target/GenericOpcodes.td|  6 ++
 .../Target/GlobalISel/SelectionDAGCompat.td   |  1 +
 .../include/llvm/Target/TargetSelectionDAG.td |  3 +
 llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp  |  2 +
 llvm/lib/CodeGen/IntrinsicLowering.cpp|  6 ++
 llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp |  6 +-
 .../SelectionDAG/LegalizeIntegerTypes.cpp |  7 ++-
 llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h |  2 +-
 .../SelectionDAG/SelectionDAGBuilder.cpp  |  8 +++
 .../SelectionDAG/SelectionDAGDumper.cpp   |  1 +
 llvm/lib/CodeGen/TargetLoweringBase.cpp   |  3 +
 .../lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp |  2 +
 .../Target/AMDGPU/AMDGPURegisterBankInfo.cpp  |  1 +
 llvm/lib/Target/AMDGPU/SIISelLowering.cpp |  4 ++
 llvm/lib/Target/AMDGPU/SMInstructions.td  | 14 +
 llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp   |  3 +
 llvm/lib/Target/NVPTX/NVPTXInstrInfo.td   |  1 -
 llvm/lib/Target/NVPTX/NVPTXIntrinsics.td  |  4 ++
 .../GlobalISel/legalizer-info-validation.mir  |  3 +
 llvm/test/CodeGen/AMDGPU/readsteadycounter.ll | 24 +++
 llvm/test/CodeGen/NVPTX/intrinsics.ll | 12 
 .../builtins/match-table-replacerreg.td   | 24 +++
 .../match-table-imms.td   | 32 +-
 .../match-table-intrinsics.td |  5 +-
 .../match-table-patfrag-root.td   |  4 +-
 .../GlobalISelCombinerEmitter/match-table.td  | 62 +--
 llvm/test/TableGen/GlobalISelEmitter.td   |  2 +-
 34 files changed, 228 insertions(+), 72 deletions(-)
 create mode 100644 llvm/test/CodeGen/AMDGPU/readsteadycounter.ll

diff --git a/clang/docs/LanguageExtensions.rst 
b/clang/docs/LanguageExtensions.rst
index e91156837290f7..4cc73599f9bae0 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -2764,6 +2764,37 @@ Query for this feature with 
``__has_builtin(__builtin_readcyclecounter)``. Note
 that even if present, its use may depend on run-time privilege or other OS
 controlled state.
 
+``__builtin_readsteadycounter``
+--
+
+``__builtin_readsteadycounter`` is used to access the fixed frequency counter
+register (or a similar steady-rate clock) on those targets that support it.
+The function is similar to ``__builtin_readcyclecounter`` above except that the
+frequency is fixed, making it suitable for measuring elapsed time.
+
+**Syntax**:
+
+.. code-block:: c++
+
+  __builtin_readsteadycounter()
+
+**Example of Use**:
+
+.. code-block:: c++
+
+  unsigned long long t0 = __builtin_readsteadycounter();
+  do_something();
+  unsigned long long t1 = __builtin_readsteadycounter();
+  unsigned long long secs_to_do_something = (t1 - t0) / tick_rate;
+
+**Description**:
+
+The ``__builtin_readsteadycounter()`` builtin returns the frequency counter 
value.
+When not supported by the target, the return value is always zero. This builtin
+takes no arguments and produces an unsigned long long result.
+
+Query for this feature with ``__has_builtin(__builtin_readsteadycounter)``.
+
 ``__builtin_dump_struct``
 -
 
diff --git a/clang/include/clang/Basic/Builtins.td 
b/clang/include/clang/Basic/Builtins.td
index 31a2bdeb2d3e5e..193d5851f9f29f 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -1110,6 +1110,12 @@ def ReadCycleCounter : Builtin {
   let Prototype = "unsigned long long int()";
 }
 
+def ReadSteadyCounter : Builtin {
+  let Spellings = ["__builtin_readsteadycounter"];
+  let Attributes = [NoThrow];
+  let Prototype = "unsigned long long int()";
+}
+
 def Trap : Builtin {
   let Spellings = ["__builtin_trap"];
   let Attributes = [NoThrow, NoReturn];
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index a7a410dab1a018..ee0b7504769622 100644
---

[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Joseph Huber via cfe-commits 

jhuber6 wrote:

> Are we assuming any particular relationship to __builtin_readcyclecounter in 
> terms of scales etc?
> 
> __builtin_readsteadycounter could be used to access x86 MPERF clock counters, 
> but to access the corresponding APERF clock we'd then need a 
> __builtin_readvariablecounter equivalent (__builtin_readcyclecounter gives 
> the separate RDTSC clock value)

Not currently at least. The idea is just to expose the counter that has a fixed 
tick rate, compared to the cycle counter which is variable.

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-12 Thread Simon Pilgrim via cfe-commits 

RKSimon wrote:

Are we assuming any particular relationship to __builtin_readcyclecounter in 
terms of scales etc? 

__builtin_readsteadycounter could be used to access x86 MPERF clock counters, 
but to access the corresponding APERF clock we'd then need a 
__builtin_readvariablecounter equivalent (__builtin_readcyclecounter gives the 
separate RDTSC clock value)

https://github.com/llvm/llvm-project/pull/81331
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[clang] [llvm] [LLVM] Add `__builtin_readsteadycounter` intrinsic and builtin for realtime clocks (PR #81331)

2024-02-11 Thread Matt Arsenault via cfe-commits 

https://github.com/arsenm edited https://github.com/llvm/llvm-project/pull/81331
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