diff --git a/utils/bazel/llvm-project-overlay/llvm/BUILD.bazel b/utils/bazel/llvm-project-overlay/llvm/BUILD.bazel
--- a/utils/bazel/llvm-project-overlay/llvm/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/llvm/BUILD.bazel
@@ -6,6 +6,7 @@
 load(":tblgen.bzl", "gentbl")
 load(":config.bzl", "llvm_config_defines")
 load(":targets.bzl", "llvm_targets")
+load(":enum_targets_gen.bzl", "enum_targets_gen")
 load(":binary_alias.bzl", "binary_alias")
 
 package(
@@ -24,22 +25,20 @@
     "$(STACK_FRAME_UNLIMITED)",
 ]
 
-template_rule(
+enum_targets_gen(
     name = "targets_def_gen",
     src = "include/llvm/Config/Targets.def.in",
     out = "include/llvm/Config/Targets.def",
-    substitutions = {
-        "@LLVM_ENUM_TARGETS@": "\n".join(["LLVM_TARGET({})".format(t) for t in llvm_targets]),
-    },
+    macro_name = "TARGET",
+    targets = llvm_targets,
 )
 
-template_rule(
+enum_targets_gen(
     name = "asm_printers_def_gen",
     src = "include/llvm/Config/AsmPrinters.def.in",
     out = "include/llvm/Config/AsmPrinters.def",
-    substitutions = {
-        "@LLVM_ENUM_ASM_PRINTERS@": "\n".join(["LLVM_ASM_PRINTER({})".format(t) for t in llvm_targets]),
-    },
+    macro_name = "ASM_PRINTER",
+    targets = llvm_targets,
 )
 
 # List of targets with ASM parsers, filtered to our list of overall targets.
@@ -57,13 +56,12 @@
     "X86",
 ] if t in llvm_targets]
 
-template_rule(
+enum_targets_gen(
     name = "asm_parsers_def_gen",
     src = "include/llvm/Config/AsmParsers.def.in",
     out = "include/llvm/Config/AsmParsers.def",
-    substitutions = {
-        "@LLVM_ENUM_ASM_PARSERS@": "\n".join(["LLVM_ASM_PARSER({})".format(t) for t in llvm_target_asm_parsers]),
-    },
+    macro_name = "ASM_PARSER",
+    targets = llvm_target_asm_parsers,
 )
 
 # List of targets with disassemblers, filtered to our list of overall targets.
@@ -81,13 +79,12 @@
     "X86",
 ] if t in llvm_targets]
 
-template_rule(
+enum_targets_gen(
     name = "disassemblers_def_gen",
     src = "include/llvm/Config/Disassemblers.def.in",
     out = "include/llvm/Config/Disassemblers.def",
-    substitutions = {
-        "@LLVM_ENUM_DISASSEMBLERS@": "\n".join(["LLVM_DISASSEMBLER({})".format(t) for t in llvm_target_disassemblers]),
-    },
+    macro_name = "DISASSEMBLER",
+    targets = llvm_target_disassemblers,
 )
 
 # TODO: Need to replace this with something that actually extracts the git
diff --git a/utils/bazel/llvm-project-overlay/llvm/enum_targets_gen.bzl b/utils/bazel/llvm-project-overlay/llvm/enum_targets_gen.bzl
new file mode 100644
--- /dev/null
+++ b/utils/bazel/llvm-project-overlay/llvm/enum_targets_gen.bzl
@@ -0,0 +1,64 @@
+# This file is licensed under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+"""A rule to expand LLVM target enumerations.
+
+Replaces in a text file a single variable of the style `@LLVM_ENUM_FOOS@` with a
+list of macro invocations, one for each target on its own line:
+
+```
+LLVM_FOO(TARGET1)
+LLVM_FOO(TARGET2)
+// ...
+```
+
+Example:
+load(":enum_targets_gen.bzl", "enum_targets_gen")
+
+enum_targets_gen(
+    name = "disassemblers_def_gen",
+    src = "include/llvm/Config/Disassemblers.def.in",
+    out = "include/llvm/Config/Disassemblers.def",
+    macro_name = "DISASSEMBLER",
+    targets = llvm_target_disassemblers,
+)
+
+This rule provides a slightly more semantic API than template_rule, but the main
+reason it exists is to permit a list with selects to be passed for `targets` as
+a select is not allowed to be passed to a rule within another data structure. 
+"""
+
+def enum_targets_gen_impl(ctx):
+    to_replace = "@LLVM_ENUM_{}S@".format(ctx.attr.macro_name)
+    replacement = "\n".join([
+        "LLVM_{}({})\n".format(ctx.attr.macro_name, t)
+        for t in ctx.attr.targets
+    ])
+
+    ctx.actions.expand_template(
+        template = ctx.file.src,
+        output = ctx.outputs.out,
+        substitutions = {to_replace: replacement},
+    )
+
+enum_targets_gen = rule(
+    attrs = {
+        "src": attr.label(
+            mandatory = True,
+            allow_single_file = True,
+        ),
+        "out": attr.output(mandatory = True),
+        "targets": attr.string_list(mandatory = True),
+        "macro_name": attr.string(
+            mandatory = True,
+            doc = "The name of the enumeration. This is the suffix of the" +
+                  " placeholder being replaced `@LLVM_ENUM_{}S@` and of the" +
+                  " macro invocations generated `LLVM_{}(TARGET)`. Should be" +
+                  " all caps and singular, e.g. 'DISASSEMBLER'",
+        ),
+    },
+    # output_to_genfiles is required for header files.
+    output_to_genfiles = True,
+    implementation = enum_targets_gen_impl,
+)