[MLIR][LLVM] Add inline_hint as a first class function attribute

[mmha]

We have noinline and alwaysinline present as first class function attributes. Add inline_hint to the list of function attributes as well.

Update the module import and translation to support the new attribute.

The verifier does not need to be changed as inlinehint does not conflict with noinline or alwaysinline.

inline_hint is needed to support the inline C/C++ keyword in CIR.

[llvmbot]

@llvm/pr-subscribers-mlir-llvm

@llvm/pr-subscribers-mlir

Author: Morris Hafner (mmha)

Changes

We have noinline and alwaysinline present as first class function attributes. Add inline_hint to the list of function attributes as well.

Update the module import and translation to support the new attribute.

The verifier does not need to be changed as inlinehint does not conflict with noinline or alwaysinline.

inline_hint is needed to support the inline C/C++ keyword in CIR.

---

Full diff: https://github.com/llvm/llvm-project/pull/163324.diff

5 Files Affected:

• (modified) mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td (+4)
• (modified) mlir/lib/Target/LLVMIR/ModuleImport.cpp (+3)
• (modified) mlir/lib/Target/LLVMIR/ModuleTranslation.cpp (+2)
• (modified) mlir/test/Target/LLVMIR/Import/function-attributes.ll (+6)
• (modified) mlir/test/Target/LLVMIR/llvmir.mlir (+11)

diff --git a/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td b/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
index 9753dca67c23d..a02f14809fcff 100644
--- a/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
+++ b/mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
@@ -1985,6 +1985,7 @@ def LLVM_LLVMFuncOp : LLVM_Op<"func", [
     OptionalAttr<StrAttr>:$instrument_function_exit,
     OptionalAttr<UnitAttr>:$no_inline,
     OptionalAttr<UnitAttr>:$always_inline,
+    OptionalAttr<UnitAttr>:$inline_hint,
     OptionalAttr<UnitAttr>:$no_unwind,
     OptionalAttr<UnitAttr>:$will_return,
     OptionalAttr<UnitAttr>:$optimize_none,
@@ -2037,6 +2038,9 @@ def LLVM_LLVMFuncOp : LLVM_Op<"func", [
     /// Returns true if the `always_inline` attribute is set, false otherwise.
     bool isAlwaysInline() { return bool(getAlwaysInlineAttr()); }
 
+    /// Returns true if the `inline_hint` attribute is set, false otherwise.
+    bool isInlineHint() { return bool(getInlineHintAttr()); }
+
     /// Returns true if the `optimize_none` attribute is set, false otherwise.
     bool isOptimizeNone() { return bool(getOptimizeNoneAttr()); }
   }];
diff --git a/mlir/lib/Target/LLVMIR/ModuleImport.cpp b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
index 9603813e059d3..857e31be6f259 100644
--- a/mlir/lib/Target/LLVMIR/ModuleImport.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleImport.cpp
@@ -2604,6 +2604,7 @@ static constexpr std::array kExplicitLLVMFuncOpAttributes{
     StringLiteral("denormal-fp-math-f32"),
     StringLiteral("fp-contract"),
     StringLiteral("frame-pointer"),
+    StringLiteral("inlinehint"),
     StringLiteral("instrument-function-entry"),
     StringLiteral("instrument-function-exit"),
     StringLiteral("memory"),
@@ -2643,6 +2644,8 @@ void ModuleImport::processFunctionAttributes(llvm::Function *func,
     funcOp.setNoInline(true);
   if (func->hasFnAttribute(llvm::Attribute::AlwaysInline))
     funcOp.setAlwaysInline(true);
+  if (func->hasFnAttribute(llvm::Attribute::InlineHint))
+    funcOp.setInlineHint(true);
   if (func->hasFnAttribute(llvm::Attribute::OptimizeNone))
     funcOp.setOptimizeNone(true);
   if (func->hasFnAttribute(llvm::Attribute::Convergent))
diff --git a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
index 5a3eb209f0a92..3fea701e150e3 100644
--- a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -1653,6 +1653,8 @@ static void convertFunctionAttributes(LLVMFuncOp func,
     llvmFunc->addFnAttr(llvm::Attribute::NoInline);
   if (func.getAlwaysInlineAttr())
     llvmFunc->addFnAttr(llvm::Attribute::AlwaysInline);
+  if (func.getInlineHintAttr())
+    llvmFunc->addFnAttr(llvm::Attribute::InlineHint);
   if (func.getOptimizeNoneAttr())
     llvmFunc->addFnAttr(llvm::Attribute::OptimizeNone);
   if (func.getConvergentAttr())
diff --git a/mlir/test/Target/LLVMIR/Import/function-attributes.ll b/mlir/test/Target/LLVMIR/Import/function-attributes.ll
index cc3d799bfc626..00d09baea393e 100644
--- a/mlir/test/Target/LLVMIR/Import/function-attributes.ll
+++ b/mlir/test/Target/LLVMIR/Import/function-attributes.ll
@@ -393,6 +393,12 @@ declare void @alwaysinline_attribute() alwaysinline
 
 // -----
 
+; CHECK-LABEL: @inlinehint_attribute
+; CHECK-SAME: attributes {inline_hint}
+declare void @inlinehint_attribute() inlinehint
+
+// -----
+
 ; CHECK-LABEL: @optnone_attribute
 ; CHECK-SAME: attributes {no_inline, optimize_none}
 declare void @optnone_attribute() noinline optnone
diff --git a/mlir/test/Target/LLVMIR/llvmir.mlir b/mlir/test/Target/LLVMIR/llvmir.mlir
index 69814f2748e1d..cc243c86ca902 100644
--- a/mlir/test/Target/LLVMIR/llvmir.mlir
+++ b/mlir/test/Target/LLVMIR/llvmir.mlir
@@ -2555,6 +2555,17 @@ llvm.func @always_inline() attributes { always_inline } {
 
 // -----
 
+// CHECK-LABEL: @inline_hint
+// CHECK-SAME: #[[ATTRS:[0-9]+]]
+llvm.func @inline_hint() attributes { inline_hint } {
+  llvm.return
+}
+
+// CHECK: #[[ATTRS]]
+// CHECK-SAME: inlinehint
+
+// -----
+
 // CHECK-LABEL: @optimize_none
 // CHECK-SAME: #[[ATTRS:[0-9]+]]
 llvm.func @optimize_none() attributes { no_inline, optimize_none } {

[andykaylor]

lgtm