[lld] [llvm] [driver] Allow `ld` as a driver alias to lld (PR #90515)

[Jordan Rupprecht via llvm-commits]

https://github.com/rupprecht created https://github.com/llvm/llvm-project/pull/90515

This adds a "hidden" alias kind that allows using LLD when symlinked as `ld`; however, it does not install `ld` as a symlink. This is to allow either using a mixed toolchain with both LLD and GNU ld, or a pure LLD toolchain where LLD has been installed (or symlinked) to `ld` for compatibility w/ older tools that expect `ld`.

>From f4f178bc0042ba88a036cf2b33cc4c772ac896f9 Mon Sep 17 00:00:00 2001
From: Jordan Rupprecht <rupprecht at google.com>
Date: Mon, 29 Apr 2024 19:34:31 +0000
Subject: [PATCH] [driver] Allow `ld` as a driver alias to lld

---
 lld/tools/lld/CMakeLists.txt                     | 4 ++++
 llvm/test/tools/llvm-driver/passthrough-lld.test | 2 ++
 llvm/tools/llvm-driver/CMakeLists.txt            | 5 +++++
 utils/bazel/llvm-project-overlay/llvm/driver.bzl | 2 +-
 4 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/lld/tools/lld/CMakeLists.txt b/lld/tools/lld/CMakeLists.txt
index 0f5daa78846bc7..8498a91597a930 100644
--- a/lld/tools/lld/CMakeLists.txt
+++ b/lld/tools/lld/CMakeLists.txt
@@ -42,3 +42,7 @@ endif()
 foreach(link ${LLD_SYMLINKS_TO_CREATE})
   add_lld_symlink(${link} lld)
 endforeach()
+
+if(LLVM_TOOL_LLVM_DRIVER_BUILD)
+  set_property(GLOBAL APPEND PROPERTY LLVM_DRIVER_HIDDEN_TOOL_ALIASES_lld ld)
+endif()
diff --git a/llvm/test/tools/llvm-driver/passthrough-lld.test b/llvm/test/tools/llvm-driver/passthrough-lld.test
index acd5f38784811c..b31fa4e483b92c 100644
--- a/llvm/test/tools/llvm-driver/passthrough-lld.test
+++ b/llvm/test/tools/llvm-driver/passthrough-lld.test
@@ -1,6 +1,8 @@
 # REQUIRES: llvm-driver, lld
 
 # RUN: %llvm ld.lld --help | FileCheck %s
+# RUN: %llvm ld --help | FileCheck %s
 # RUN: %llvm lld -flavor ld.lld --help | FileCheck %s
+# RUN: %llvm ld -flavor ld.lld --help | FileCheck %s
 
 # CHECK: supported targets: elf
diff --git a/llvm/tools/llvm-driver/CMakeLists.txt b/llvm/tools/llvm-driver/CMakeLists.txt
index 83e084069b96ac..82d85c7230109c 100644
--- a/llvm/tools/llvm-driver/CMakeLists.txt
+++ b/llvm/tools/llvm-driver/CMakeLists.txt
@@ -13,6 +13,11 @@ foreach(tool ${LLVM_DRIVER_TOOLS})
     string(REPLACE "llvm-" "" alias ${alias})
     set(def_decl "${def_decl}LLVM_DRIVER_TOOL(\"${alias}\", ${tool_entry})\n")
   endforeach()
+  get_property(hidden_tool_aliases GLOBAL PROPERTY LLVM_DRIVER_HIDDEN_TOOL_ALIASES_${tool})
+  foreach(alias ${hidden_tool_aliases})
+    string(REPLACE "llvm-" "" alias ${alias})
+    set(def_decl "${def_decl}LLVM_DRIVER_TOOL(\"${alias}\", ${tool_entry})\n")
+  endforeach()
 endforeach()
 
 file(WRITE
diff --git a/utils/bazel/llvm-project-overlay/llvm/driver.bzl b/utils/bazel/llvm-project-overlay/llvm/driver.bzl
index 888626d7cf8451..10796d91983433 100644
--- a/utils/bazel/llvm-project-overlay/llvm/driver.bzl
+++ b/utils/bazel/llvm-project-overlay/llvm/driver.bzl
@@ -37,7 +37,7 @@ _TOOLS = {
 # aliases for a given tool.
 _EXTRA_ALIASES = {
     "clang": ["clang++", "clang-cl", "clang-cpp"],
-    "lld": ["lld-link", "ld.lld", "ld64.lld", "wasm-ld"],
+    "lld": ["ld", "lld-link", "ld.lld", "ld64.lld", "wasm-ld"],
     "llvm-ar": ["ranlib", "lib", "dlltool"],
     "llvm-objcopy": ["bitcode-strip", "install-name-tool", "strip"],
     "llvm-objdump": ["otool"],