[MLIR][LLVMIR] Import: fix function attribute inheritance on call attributes

Before this PR `inst->getFnAttr(Kind)` fallbacks to check if the parent has an
attribute, which breaks roundtriping the LLVM IR. It's possible to argue that
this small optimization isn't harmful, but seems too early if it's breaking
roundtrip behavior.

Author: bcardosolopes

mlir/lib/Target/LLVMIR/ModuleImport.cpp

@@ -2263,10 +2263,15 @@ LogicalResult ModuleImport::convertInvokeAttributes(llvm::InvokeInst *inst,
 LogicalResult ModuleImport::convertCallAttributes(llvm::CallInst *inst,
                                                   CallOp op) {
   setFastmathFlagsAttr(inst, op.getOperation());
+  // Query the attributes directly instead of using `inst->getFnAttr(Kind)`, the
+  // latter does additional lookup to the parent and inherits, changing the
+  // semantics too early.
+  llvm::AttributeList callAttrs = inst->getAttributes();
+
   op.setTailCallKind(convertTailCallKindFromLLVM(inst->getTailCallKind()));
-  op.setConvergent(inst->isConvergent());
-  op.setNoUnwind(inst->doesNotThrow());
-  op.setWillReturn(inst->hasFnAttr(llvm::Attribute::WillReturn));
+  op.setConvergent(callAttrs.getFnAttr(llvm::Attribute::Convergent).isValid());
+  op.setNoUnwind(callAttrs.getFnAttr(llvm::Attribute::NoUnwind).isValid());
+  op.setWillReturn(callAttrs.getFnAttr(llvm::Attribute::WillReturn).isValid());
 
   llvm::MemoryEffects memEffects = inst->getMemoryEffects();
   ModRefInfo othermem = convertModRefInfoFromLLVM(

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

@@ -0,0 +1,18 @@
+; RUN: mlir-translate -import-llvm -split-input-file %s | FileCheck %s
+
+%struct.S = type { i8 }
+
+; CHECK-LABEL: @t
+define void @t(i1 %0) #0 {
+  %3 = alloca %struct.S, align 1
+  ; CHECK-NOT: llvm.call @z(%1) {no_unwind} : (!llvm.ptr) -> ()
+  ; CHECK: llvm.call @z(%1) : (!llvm.ptr) -> ()
+  call void @z(ptr %3)
+  ret void
+}
+
+define linkonce_odr void @z(ptr %0) #0 {
+  ret void
+}
+
+attributes #0 = { nounwind }