[MLIR] Add the convergent attribute to LLVM Dialect (llvm#97709)

In order to use the convergent attribute in the GPUToLLVMSPV pass, I've
added the attribute to the LLVM dialect.
Some details on the convergent attribute
https://llvm.org/docs/ConvergentOperations.html#convergent-operations

Author: FMarno

mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td

@@ -1425,6 +1425,7 @@ def LLVM_LLVMFuncOp : LLVM_Op<"func", [
     UnitAttr:$dso_local,
     DefaultValuedAttr<CConv, "CConv::C">:$CConv,
     OptionalAttr<SymbolRefAttr>:$comdat,
+    OptionalAttr<UnitAttr>:$convergent,
     OptionalAttr<FlatSymbolRefAttr>:$personality,
     OptionalAttr<StrAttr>:$garbageCollector,
     OptionalAttr<ArrayAttr>:$passthrough,

mlir/lib/Target/LLVMIR/ModuleImport.cpp

@@ -1675,6 +1675,7 @@ static constexpr std::array kExplicitAttributes{
     StringLiteral("aarch64_pstate_sm_enabled"),
     StringLiteral("alwaysinline"),
     StringLiteral("approx-func-fp-math"),
+    StringLiteral("convergent"),
     StringLiteral("frame-pointer"),
     StringLiteral("no-infs-fp-math"),
     StringLiteral("no-nans-fp-math"),
@@ -1754,6 +1755,8 @@ void ModuleImport::processFunctionAttributes(llvm::Function *func,
     funcOp.setAlwaysInline(true);
   if (func->hasFnAttribute(llvm::Attribute::OptimizeNone))
     funcOp.setOptimizeNone(true);
+  if (func->hasFnAttribute(llvm::Attribute::Convergent))
+    funcOp.setConvergent(true);
 
   if (func->hasFnAttribute("aarch64_pstate_sm_enabled"))
     funcOp.setArmStreaming(true);

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

@@ -1422,6 +1422,8 @@ static void convertFunctionAttributes(LLVMFuncOp func,
     llvmFunc->addFnAttr(llvm::Attribute::AlwaysInline);
   if (func.getOptimizeNoneAttr())
     llvmFunc->addFnAttr(llvm::Attribute::OptimizeNone);
+  if (func.getConvergentAttr())
+    llvmFunc->addFnAttr(llvm::Attribute::Convergent);
   convertFunctionMemoryAttributes(func, llvmFunc);
 }
 

mlir/test/Dialect/LLVMIR/func.mlir

@@ -287,6 +287,12 @@ module {
     // CHECK-SAME: attributes {no_signed_zeros_fp_math = true}
     llvm.return
   }
+
+  llvm.func @convergent_function() attributes {convergent} {
+    // CHECK: @convergent_function
+    // CHECK-SAME: attributes {convergent}
+    llvm.return
+  }
 }
 
 // -----

mlir/test/Target/LLVMIR/Import/function-attributes.ll

@@ -361,3 +361,9 @@ declare void @alwaysinline_attribute() alwaysinline
 ; CHECK-LABEL: @optnone_attribute
 ; CHECK-SAME: attributes {no_inline, optimize_none}
 declare void @optnone_attribute() noinline optnone
+
+// -----
+
+; CHECK-LABEL: @convergent_attribute
+; CHECK-SAME: attributes {convergent}
+declare void @convergent_attribute() convergent

mlir/test/Target/LLVMIR/llvmir.mlir

@@ -2441,3 +2441,14 @@ llvm.func @optimize_none() attributes { no_inline, optimize_none } {
 
 // CHECK: #[[ATTRS]]
 // CHECK-SAME: optnone
+
+// -----
+
+// CHECK-LABEL: @convergent
+// CHECK-SAME: #[[ATTRS:[0-9]+]]
+llvm.func @convergent() attributes { convergent } {
+  llvm.return
+}
+
+// CHECK: #[[ATTRS]]
+// CHECK-SAME: convergent