Add cmake comments and a test

Author: rolfmorel

mlir/include/mlir/Dialect/LLVMIR/CMakeLists.txt

@@ -7,16 +7,21 @@ mlir_tablegen(LLVMOpsDialect.h.inc -gen-dialect-decls)
 mlir_tablegen(LLVMOpsDialect.cpp.inc -gen-dialect-defs)
 mlir_tablegen(LLVMOpsEnums.h.inc -gen-enum-decls)
 mlir_tablegen(LLVMOpsEnums.cpp.inc -gen-enum-defs)
+#For LLVMOpsAttrDefs.h.inc, see below.
 mlir_tablegen(LLVMOpsAttrDefs.cpp.inc -gen-attrdef-defs
               -attrdefs-dialect=llvm)
 add_public_tablegen_target(MLIRLLVMOpsIncGen)
 
-# FIXME: explain how this solves generated header recursive dependency
+# NB: Separate out LLVMOpsAttrDefs.h.inc generation as generating it
+#     through LLVMOps.td ends up defining LLVMTargetFeaturesAttr even
+#     though LLVMTargetFeaturesAttrDefs.* is responsible for that.
 set(LLVM_TARGET_DEFINITIONS LLVMAttrAndEnumDefs.td)
 mlir_tablegen(LLVMOpsAttrDefs.h.inc -gen-attrdef-decls -attrdefs-dialect=llvm)
 add_public_tablegen_target(MLIRLLVMAttrsIncGen)
 
-# FIXME: explain how this solves generated header recursive dependency
+# NB: LLVMTargetFeaturesAttr is split out into its own file
+#     to break a recursive dependency: LLVMInterfaces depends
+#     on it, and other LLVMAttrs depending on LLVMInterfaces.
 set(LLVM_TARGET_DEFINITIONS LLVMTargetFeaturesAttrDefs.td)
 mlir_tablegen(LLVMTargetFeaturesAttrDefs.h.inc -gen-attrdef-decls)
 mlir_tablegen(LLVMTargetFeaturesAttrDefs.cpp.inc -gen-attrdef-defs)

mlir/test/Dialect/LLVMIR/data-layout-from-target.mlir

@@ -12,8 +12,36 @@ module attributes { llvm.target = #llvm.target<triple = "x86_64-unknown-linux">
 
 // -----
 
+// TODO: module attributes
+// TODO-SAME: dlti.dl_spec = #llvm.data_layout
+// TODO-SAME: llvm.target = #llvm.target<
+// TODO-SAME:   triple = "x86_64-unknown-linux"
+// TODO-NOT:   chip = "skylake"
+// TODO-SAME:   #llvm.target_features<["+mmx", "+sse"]>
+// TODO-NOT:   chip = "skylake"
+
+//module attributes { llvm.target = #llvm.target<triple = "x86_64-unknown-linux",
+//                                               // Generated parser is dumb: expected 'chip'
+//                                               #llvm.target_features<["+mmx", "+sse"]>> } {
+//}
+
+// -----
+
 // CHECK: module attributes
-// CHECK-SAME: dlti.dl_spec = #llvm.data_layout<"[[DL_STR:.*]]">
+// CHECK-SAME: dlti.dl_spec = #llvm.data_layout
+// CHECK-SAME: llvm.target = #llvm.target<
+// CHECK-SAME:   triple = "x86_64-unknown-linux"
+// CHECK-SAME:   chip = "skylake"
+// CHECK-NOT:    #llvm.target_features
+
+module attributes { llvm.target = #llvm.target<triple = "x86_64-unknown-linux",
+                                               chip = "skylake"> } {
+}
+
+// -----
+
+// CHECK: module attributes
+// CHECK-SAME: dlti.dl_spec = #llvm.data_layout
 // CHECK-SAME: llvm.target = #llvm.target<
 // CHECK-SAME:   triple = "x86_64-unknown-linux"
 // CHECK-SAME:   chip = "skylake"