[clang] [Driver] Search for compiler-rt libraries in sysroot/lib if not found in the resource directory (PR #132443)

[Kostiantyn Lazukin via cfe-commits]

https://github.com/Sunday111 updated https://github.com/llvm/llvm-project/pull/132443

>From 9a88ff05af21a5d5357780293f2d011ffe457041 Mon Sep 17 00:00:00 2001
From: Kostiantyn Lazukin
 <koslaz01 at ip-10-252-21-142.eu-west-1.compute.internal>
Date: Thu, 20 Mar 2025 16:54:06 +0000
Subject: [PATCH] [Driver] Search for compiler-rt libraries in sysroot/lib if
 not found in the resource directory

This patch improves support for embedded Linux toolchains with multiple
sysroots, each containing different built-in libraries. If compiler-rt
libraries are not found in the resource directory, the Clang driver will
fallback to searching in the sysroot/lib directory.

This change preserves the standard behavior for regular Linux toolchains
while allowing greater flexibility in toolchains with multiple sysroots.
---
 clang/lib/Driver/ToolChains/Linux.cpp                 |  2 ++
 .../Inputs/musl_sysroot_with_builtins/lib/Scrt1.o     |  0
 .../lib/clang_rt.crtbegin.o                           |  0
 .../musl_sysroot_with_builtins/lib/clang_rt.crtend.o  |  0
 .../Inputs/musl_sysroot_with_builtins/lib/crti.o      |  0
 .../Inputs/musl_sysroot_with_builtins/lib/crtn.o      |  0
 .../lib/libclang_rt.builtins.a                        |  0
 clang/test/Driver/Inputs/resource_dir_empty/keep      |  0
 clang/test/Driver/linux-musl-library-search.cpp       | 11 +++++++++++
 9 files changed, 13 insertions(+)
 create mode 100644 clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/Scrt1.o
 create mode 100644 clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/clang_rt.crtbegin.o
 create mode 100644 clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/clang_rt.crtend.o
 create mode 100644 clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/crti.o
 create mode 100644 clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/crtn.o
 create mode 100644 clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/libclang_rt.builtins.a
 create mode 100644 clang/test/Driver/Inputs/resource_dir_empty/keep
 create mode 100644 clang/test/Driver/linux-musl-library-search.cpp

diff --git a/clang/lib/Driver/ToolChains/Linux.cpp b/clang/lib/Driver/ToolChains/Linux.cpp
index 1e9bd3de75f04..1bd8daafa8091 100644
--- a/clang/lib/Driver/ToolChains/Linux.cpp
+++ b/clang/lib/Driver/ToolChains/Linux.cpp
@@ -354,6 +354,8 @@ Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
 
   addPathIfExists(D, concat(SysRoot, "/lib"), Paths);
   addPathIfExists(D, concat(SysRoot, "/usr/lib"), Paths);
+
+  addPathIfExists(D, concat(SysRoot, "/lib"), getLibraryPaths());
 }
 
 ToolChain::RuntimeLibType Linux::GetDefaultRuntimeLibType() const {
diff --git a/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/Scrt1.o b/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/Scrt1.o
new file mode 100644
index 0000000000000..e69de29bb2d1d
diff --git a/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/clang_rt.crtbegin.o b/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/clang_rt.crtbegin.o
new file mode 100644
index 0000000000000..e69de29bb2d1d
diff --git a/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/clang_rt.crtend.o b/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/clang_rt.crtend.o
new file mode 100644
index 0000000000000..e69de29bb2d1d
diff --git a/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/crti.o b/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/crti.o
new file mode 100644
index 0000000000000..e69de29bb2d1d
diff --git a/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/crtn.o b/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/crtn.o
new file mode 100644
index 0000000000000..e69de29bb2d1d
diff --git a/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/libclang_rt.builtins.a b/clang/test/Driver/Inputs/musl_sysroot_with_builtins/lib/libclang_rt.builtins.a
new file mode 100644
index 0000000000000..e69de29bb2d1d
diff --git a/clang/test/Driver/Inputs/resource_dir_empty/keep b/clang/test/Driver/Inputs/resource_dir_empty/keep
new file mode 100644
index 0000000000000..e69de29bb2d1d
diff --git a/clang/test/Driver/linux-musl-library-search.cpp b/clang/test/Driver/linux-musl-library-search.cpp
new file mode 100644
index 0000000000000..7bfdc58af1dcd
--- /dev/null
+++ b/clang/test/Driver/linux-musl-library-search.cpp
@@ -0,0 +1,11 @@
+// RUN: %clang -### %s 2>&1 \
+// RUN:     --target=aarch64-unknown-linux-musl \
+// RUN:     -ccc-install-dir %S/Inputs/basic_linux_tree/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_empty \
+// RUN:     --sysroot=%S/Inputs/musl_sysroot_with_builtins \
+// RUN:     -static \
+// RUN:     -rtlib=compiler-rt \
+// RUN:   | FileCheck %s
+
+// CHECK-DAG: "--sysroot={{[^"]+}}/Inputs/musl_sysroot_with_builtins"
+// CHECK-DAG: "{{[^"]+}}/Inputs/musl_sysroot_with_builtins/lib/libclang_rt.builtins.a"