[Mlir-commits] [mlir] [mlir][llvm] Add llvm.target_features features attribute (PR #71510)
Benjamin Maxwell
llvmlistbot at llvm.org
Tue Nov 7 02:43:23 PST 2023
https://github.com/MacDue created https://github.com/llvm/llvm-project/pull/71510
This patch adds a target_features (TargetFeaturesAttr) to the LLVM dialect to allow setting and querying the features in use on a function.
The features are stored as a sorted list rather plain string to allow efficiently checking a function's features.
The motivation for this comes from the Arm SME dialect where we would like a convenient way to check what variants of an operation are available based on the CPU features.
Intended usage:
The target_features attribute is populated manually or by a pass:
```mlir
func.func @example() attributes {
target_features = #llvm.target_features<"+sme,+sve,+sme-f64f64">
} {
// ...
}
```
Then within a later rewrite the attribute can be checked, and used to make lowering decisions.
```c++
// Finds the "target_features" attribute on the parent
// FunctionOpInterface.
auto targetFeatures = LLVM::TargetFeaturesAttr::featuresAt(op);
// Check a feature.
// Returns false if targetFeatures is null or the feature is not in
// the list.
if (!targetFeatures.contains("+sme-f64f64"))
return failure();
```
For now, this is rather simple just checks if the exact feature is in the list, though it could be possible to extend with implied features using information from LLVM.
>From 442bbec51c217a30d040e6e1fa6cad50264fe259 Mon Sep 17 00:00:00 2001
From: Benjamin Maxwell <benjamin.maxwell at arm.com>
Date: Tue, 7 Nov 2023 10:38:52 +0000
Subject: [PATCH] [mlir][llvm] Add llvm.target_features features attribute
This patch adds a target_features (TargetFeaturesAttr) to the LLVM
dialect to allow setting and querying the features in use on a function.
The features are stored as a sorted list rather plain string to allow
efficiently checking a function's features.
The motivation for this comes from the Arm SME dialect where we would
like a convenient way to check what variants of an operation are
available based on the CPU features.
Intended usage:
The target_features attribute is populated manually or by a pass:
```mlir
func.func @example() attributes {
target_features = #llvm.target_features<"+sme,+sve,+sme-f64f64">
} {
// ...
}
```
Then within a later rewrite the attribute can be checked, and used to
make lowering decisions.
```c++
// Finds the "target_features" attribute on the parent
// FunctionOpInterface.
auto targetFeatures = LLVM::TargetFeaturesAttr::featuresAt(op);
// Check a feature.
// Returns false if targetFeatures is null or the feature is not in
// the list.
if (!targetFeatures.contains("+sme-f64f64"))
return failure();
```
For now, this is rather simple just checks if the exact feature is in
the list, though it could be possible to extend with implied features
using information from LLVM.
---
.../mlir/Dialect/LLVMIR/LLVMAttrDefs.td | 53 ++++++++++++++
mlir/include/mlir/Dialect/LLVMIR/LLVMAttrs.h | 25 +++++++
mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td | 3 +-
mlir/lib/Dialect/LLVMIR/IR/LLVMAttrs.cpp | 69 +++++++++++++++++++
mlir/lib/Target/LLVMIR/ModuleImport.cpp | 25 +++++--
mlir/lib/Target/LLVMIR/ModuleTranslation.cpp | 3 +
.../Target/LLVMIR/Import/target-features.ll | 9 +++
mlir/test/Target/LLVMIR/target-features.mlir | 7 ++
8 files changed, 186 insertions(+), 8 deletions(-)
create mode 100644 mlir/test/Target/LLVMIR/Import/target-features.ll
create mode 100644 mlir/test/Target/LLVMIR/target-features.mlir
diff --git a/mlir/include/mlir/Dialect/LLVMIR/LLVMAttrDefs.td b/mlir/include/mlir/Dialect/LLVMIR/LLVMAttrDefs.td
index 0d9af88157a8ae1..e0f4518abf3c01f 100644
--- a/mlir/include/mlir/Dialect/LLVMIR/LLVMAttrDefs.td
+++ b/mlir/include/mlir/Dialect/LLVMIR/LLVMAttrDefs.td
@@ -860,4 +860,57 @@ def LLVM_VScaleRangeAttr : LLVM_Attr<"VScaleRange", "vscale_range"> {
"IntegerAttr":$maxRange);
let assemblyFormat = "`<` struct(params) `>`";
}
+
+//===----------------------------------------------------------------------===//
+// TargetFeaturesAttr
+//===----------------------------------------------------------------------===//
+
+def LLVM_TargetFeaturesAttr : LLVM_Attr<"TargetFeatures", "target_features"> {
+ let summary = "LLVM target features attribute";
+
+ let description = [{
+ Represents the LLVM target features in a manner that is efficient to query.
+
+ Example:
+ ```mlir
+ #llvm.target_features<"+sme,+sve,+sme-f64f64">
+ ```
+
+ Then within a pass or rewrite the features active at an op can be queried:
+
+ ```c++
+ auto targetFeatures = LLVM::TargetFeaturesAttr::featuresAt(op);
+
+ if (!targetFeatures.contains("+sme-f64f64"))
+ return failure();
+ ```
+ }];
+
+ let parameters = (ins
+ ArrayRefOfSelfAllocationParameter<"TargetFeature", "">: $features);
+
+ let builders = [
+ TypeBuilder<(ins "::llvm::ArrayRef<TargetFeature>": $features)>,
+ TypeBuilder<(ins "StringRef": $features)>
+ ];
+
+ let extraClassDeclaration = [{
+ /// Checks if a feature is contained within the features list.
+ bool contains(TargetFeature) const;
+ bool contains(StringRef feature) const {
+ return contains(TargetFeature{feature});
+ }
+
+ /// Returns the list of features as an LLVM-compatible string.
+ std::string getFeaturesString() const;
+
+ /// Finds the target features on the parent FunctionOpInterface.
+ /// Note: This assumes the attribute is called "target_features".
+ static TargetFeaturesAttr featuresAt(Operation* op);
+ }];
+
+ let hasCustomAssemblyFormat = 1;
+ let skipDefaultBuilders = 1;
+}
+
#endif // LLVMIR_ATTRDEFS
diff --git a/mlir/include/mlir/Dialect/LLVMIR/LLVMAttrs.h b/mlir/include/mlir/Dialect/LLVMIR/LLVMAttrs.h
index c370bfa2b733d65..68a3d1f74175bda 100644
--- a/mlir/include/mlir/Dialect/LLVMIR/LLVMAttrs.h
+++ b/mlir/include/mlir/Dialect/LLVMIR/LLVMAttrs.h
@@ -74,6 +74,31 @@ class TBAANodeAttr : public Attribute {
}
};
+/// This struct represents a single LLVM target feature.
+struct TargetFeature {
+ StringRef feature;
+
+ // Support allocating this struct into MLIR storage to ensure the feature
+ // string remains valid.
+ TargetFeature allocateInto(TypeStorageAllocator &alloc) const {
+ return TargetFeature{alloc.copyInto(feature)};
+ }
+
+ operator StringRef() const { return feature; }
+
+ bool operator==(TargetFeature const &other) const {
+ return feature == other.feature;
+ }
+
+ bool operator<(TargetFeature const &other) const {
+ return feature < other.feature;
+ }
+};
+
+inline llvm::hash_code hash_value(const TargetFeature &feature) {
+ return llvm::hash_value(feature.feature);
+}
+
// Inline the LLVM generated Linkage enum and utility.
// This is only necessary to isolate the "enum generated code" from the
// attribute definition itself.
diff --git a/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td b/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
index 7928bb940ad8bae..a6338485a52d9f5 100644
--- a/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
+++ b/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
@@ -1388,7 +1388,8 @@ def LLVM_LLVMFuncOp : LLVM_Op<"func", [
OptionalAttr<StrAttr>:$section,
OptionalAttr<UnnamedAddr>:$unnamed_addr,
OptionalAttr<I64Attr>:$alignment,
- OptionalAttr<LLVM_VScaleRangeAttr>:$vscale_range
+ OptionalAttr<LLVM_VScaleRangeAttr>:$vscale_range,
+ OptionalAttr<LLVM_TargetFeaturesAttr>:$target_features
);
let regions = (region AnyRegion:$body);
diff --git a/mlir/lib/Dialect/LLVMIR/IR/LLVMAttrs.cpp b/mlir/lib/Dialect/LLVMIR/IR/LLVMAttrs.cpp
index 3d45ab8fac4d705..e97c30487210cd8 100644
--- a/mlir/lib/Dialect/LLVMIR/IR/LLVMAttrs.cpp
+++ b/mlir/lib/Dialect/LLVMIR/IR/LLVMAttrs.cpp
@@ -14,10 +14,13 @@
#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
#include "mlir/IR/Builders.h"
#include "mlir/IR/DialectImplementation.h"
+#include "mlir/Interfaces/FunctionInterfaces.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/TypeSwitch.h"
#include "llvm/BinaryFormat/Dwarf.h"
+#include <algorithm>
#include <optional>
+#include <set>
using namespace mlir;
using namespace mlir::LLVM;
@@ -109,3 +112,69 @@ bool MemoryEffectsAttr::isReadWrite() {
return false;
return true;
}
+
+//===----------------------------------------------------------------------===//
+// TargetFeaturesAttr
+//===----------------------------------------------------------------------===//
+
+Attribute TargetFeaturesAttr::parse(mlir::AsmParser &parser, mlir::Type) {
+ std::string targetFeatures;
+ if (parser.parseLess() || parser.parseString(&targetFeatures) ||
+ parser.parseGreater())
+ return {};
+ return get(parser.getContext(), targetFeatures);
+}
+
+void TargetFeaturesAttr::print(mlir::AsmPrinter &printer) const {
+ printer << "<\"";
+ llvm::interleave(
+ getFeatures(), printer,
+ [&](auto &feature) { printer << StringRef(feature); }, ",");
+ printer << "\">";
+}
+
+TargetFeaturesAttr
+TargetFeaturesAttr::get(MLIRContext *context,
+ llvm::ArrayRef<TargetFeature> featuresRef) {
+ // Sort and de-duplicate target features.
+ std::set<TargetFeature> features(featuresRef.begin(), featuresRef.end());
+ return Base::get(context, llvm::to_vector(features));
+}
+
+TargetFeaturesAttr TargetFeaturesAttr::get(MLIRContext *context,
+ StringRef targetFeatures) {
+ SmallVector<StringRef> features;
+ StringRef{targetFeatures}.split(features, ',', /*MaxSplit=*/-1,
+ /*KeepEmpty=*/false);
+ return get(context, llvm::map_to_vector(features, [](StringRef feature) {
+ return TargetFeature{feature};
+ }));
+}
+
+bool TargetFeaturesAttr::contains(TargetFeature feature) const {
+ if (!bool(*this))
+ return false; // Allows checking null target features.
+ ArrayRef<TargetFeature> features = getFeatures();
+ // Note: The attribute getter ensures the feature list is sorted.
+ return std::binary_search(features.begin(), features.end(), feature);
+}
+
+std::string TargetFeaturesAttr::getFeaturesString() const {
+ std::string features;
+ bool first = true;
+ for (TargetFeature feature : getFeatures()) {
+ if (!first)
+ features += ",";
+ features += StringRef(feature);
+ first = false;
+ }
+ return features;
+}
+
+TargetFeaturesAttr TargetFeaturesAttr::featuresAt(Operation *op) {
+ auto parentFunction = op->getParentOfType<FunctionOpInterface>();
+ if (!parentFunction)
+ return {};
+ return parentFunction.getOperation()->getAttrOfType<TargetFeaturesAttr>(
+ "target_features");
+}
diff --git a/mlir/lib/Target/LLVMIR/ModuleImport.cpp b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
index e3562049cd81c76..5eed08f371d8089 100644
--- a/mlir/lib/Target/LLVMIR/ModuleImport.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
@@ -1554,6 +1554,15 @@ static void processMemoryEffects(llvm::Function *func, LLVMFuncOp funcOp) {
funcOp.setMemoryAttr(memAttr);
}
+// List of LLVM IR attributes that map to explicit attribute on the MLIR
+// LLVMFuncOp.
+static constexpr std::array ExplicitAttributes{
+ StringLiteral("aarch64_pstate_sm_enabled"),
+ StringLiteral("aarch64_pstate_sm_body"),
+ StringLiteral("vscale_range"),
+ StringLiteral("target-features"),
+};
+
static void processPassthroughAttrs(llvm::Function *func, LLVMFuncOp funcOp) {
MLIRContext *context = funcOp.getContext();
SmallVector<Attribute> passthroughs;
@@ -1579,11 +1588,8 @@ static void processPassthroughAttrs(llvm::Function *func, LLVMFuncOp funcOp) {
attrName = llvm::Attribute::getNameFromAttrKind(attr.getKindAsEnum());
auto keyAttr = StringAttr::get(context, attrName);
- // Skip the aarch64_pstate_sm_<body|enabled> since the LLVMFuncOp has an
- // explicit attribute.
- // Also skip the vscale_range, it is also an explicit attribute.
- if (attrName == "aarch64_pstate_sm_enabled" ||
- attrName == "aarch64_pstate_sm_body" || attrName == "vscale_range")
+ // Skip attributes that map to an explicit attribute on the LLVMFuncOp.
+ if (llvm::is_contained(ExplicitAttributes, attrName))
continue;
if (attr.isStringAttribute()) {
@@ -1623,14 +1629,19 @@ void ModuleImport::processFunctionAttributes(llvm::Function *func,
funcOp.setArmStreaming(true);
else if (func->hasFnAttribute("aarch64_pstate_sm_body"))
funcOp.setArmLocallyStreaming(true);
- llvm::Attribute attr = func->getFnAttribute(llvm::Attribute::VScaleRange);
- if (attr.isValid()) {
+ if (llvm::Attribute attr = func->getFnAttribute(llvm::Attribute::VScaleRange);
+ attr.isValid()) {
MLIRContext *context = funcOp.getContext();
auto intTy = IntegerType::get(context, 32);
funcOp.setVscaleRangeAttr(LLVM::VScaleRangeAttr::get(
context, IntegerAttr::get(intTy, attr.getVScaleRangeMin()),
IntegerAttr::get(intTy, attr.getVScaleRangeMax().value_or(0))));
}
+ if (llvm::Attribute attr = func->getFnAttribute("target-features");
+ attr.isStringAttribute()) {
+ funcOp.setTargetFeaturesAttr(
+ LLVM::TargetFeaturesAttr::get(context, attr.getValueAsString()));
+ }
}
DictionaryAttr
diff --git a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
index 7312388bc9b4dd2..3282857a6eb2991 100644
--- a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -890,6 +890,9 @@ LogicalResult ModuleTranslation::convertOneFunction(LLVMFuncOp func) {
else if (func.getArmLocallyStreaming())
llvmFunc->addFnAttr("aarch64_pstate_sm_body");
+ if (auto targetFeatures = func.getTargetFeatures())
+ llvmFunc->addFnAttr("target-features", targetFeatures->getFeaturesString());
+
if (auto attr = func.getVscaleRange())
llvmFunc->addFnAttr(llvm::Attribute::getWithVScaleRangeArgs(
getLLVMContext(), attr->getMinRange().getInt(),
diff --git a/mlir/test/Target/LLVMIR/Import/target-features.ll b/mlir/test/Target/LLVMIR/Import/target-features.ll
new file mode 100644
index 000000000000000..39e9a1204d3e022
--- /dev/null
+++ b/mlir/test/Target/LLVMIR/Import/target-features.ll
@@ -0,0 +1,9 @@
+; RUN: mlir-translate -import-llvm -split-input-file %s | FileCheck %s
+
+; CHECK-LABEL: llvm.func @target_features()
+; CHECK-SAME: #llvm.target_features<"+sme,+sme-f64f64,+sve">
+define void @target_features() #0 {
+ ret void
+}
+
+attributes #0 = { "target-features"="+sme,+sme-f64f64,+sve" }
diff --git a/mlir/test/Target/LLVMIR/target-features.mlir b/mlir/test/Target/LLVMIR/target-features.mlir
new file mode 100644
index 000000000000000..02c07d27ca3cd84
--- /dev/null
+++ b/mlir/test/Target/LLVMIR/target-features.mlir
@@ -0,0 +1,7 @@
+// RUN: mlir-translate -mlir-to-llvmir %s | FileCheck %s
+
+// CHECK-LABEL: define void @target_features
+// CHECK: attributes #{{.*}} = { "target-features"="+sme,+sme-f64f64,+sve" }
+llvm.func @target_features() attributes { target_features = #llvm.target_features<"+sme,+sve,+sme-f64f64"> } {
+ llvm.return
+}
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