[clang] [clang][flang][windows] Prefer user-provided library paths (-L) (PR #90758)

[David Truby via cfe-commits]

https://github.com/DavidTruby updated https://github.com/llvm/llvm-project/pull/90758

>From 0afdbb7dac3a3a051661d5747c8c6470a13f1e0c Mon Sep 17 00:00:00 2001
From: David Truby <david at truby.dev>
Date: Wed, 1 May 2024 19:41:47 +0100
Subject: [PATCH 1/2] [clang][flang][windows] Prefer user-provided library
 paths (-L)

Currently the paths to compiler-rt and the Flang runtimes from the LLVM
build/install directory are preferred over any user-provided library
paths. This means a user can't override compiler-rt or the Flang
runtimes with custom versions.

This patch changes the link order to prefer library paths specified
with -L over the LLVM paths. This matches the behaviour of clang
and flang on Linux.
---
 clang/lib/Driver/ToolChains/MSVC.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/MSVC.cpp b/clang/lib/Driver/ToolChains/MSVC.cpp
index fbf2f45b543844..b7021d4b996ddd 100644
--- a/clang/lib/Driver/ToolChains/MSVC.cpp
+++ b/clang/lib/Driver/ToolChains/MSVC.cpp
@@ -134,6 +134,10 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
           Args.MakeArgString(std::string("-libpath:") + WindowsSdkLibPath));
   }
 
+  if (!C.getDriver().IsCLMode() && Args.hasArg(options::OPT_L))
+    for (const auto &LibPath : Args.getAllArgValues(options::OPT_L))
+      CmdArgs.push_back(Args.MakeArgString("-libpath:" + LibPath));
+
   if (C.getDriver().IsFlangMode()) {
     addFortranRuntimeLibraryPath(TC, Args, CmdArgs);
     addFortranRuntimeLibs(TC, Args, CmdArgs);
@@ -154,10 +158,6 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   if (TC.getVFS().exists(CRTPath))
     CmdArgs.push_back(Args.MakeArgString("-libpath:" + CRTPath));
 
-  if (!C.getDriver().IsCLMode() && Args.hasArg(options::OPT_L))
-    for (const auto &LibPath : Args.getAllArgValues(options::OPT_L))
-      CmdArgs.push_back(Args.MakeArgString("-libpath:" + LibPath));
-
   CmdArgs.push_back("-nologo");
 
   if (Args.hasArg(options::OPT_g_Group, options::OPT__SLASH_Z7))

>From 5cf9a46d2b67520a33740de1e12a665a1665d932 Mon Sep 17 00:00:00 2001
From: David Truby <david at truby.dev>
Date: Fri, 3 May 2024 14:29:45 +0100
Subject: [PATCH 2/2] Add tests

---
 clang/test/Driver/flang/msvc-link.f90 | 8 ++++++++
 clang/test/Driver/msvc-link.cpp       | 7 +++++++
 2 files changed, 15 insertions(+)
 create mode 100644 clang/test/Driver/flang/msvc-link.f90
 create mode 100644 clang/test/Driver/msvc-link.cpp

diff --git a/clang/test/Driver/flang/msvc-link.f90 b/clang/test/Driver/flang/msvc-link.f90
new file mode 100644
index 00000000000000..6a1af043e9d2b6
--- /dev/null
+++ b/clang/test/Driver/flang/msvc-link.f90
@@ -0,0 +1,8 @@
+! REQUIRES: system-windows
+!
+! RUN: %clang --driver-mode=flang -### %s -Ltest 2>&1 | FileCheck %s
+!
+! Test that user provided paths come before the Flang runtimes and compiler-rt
+! CHECK: "-libpath:test"
+! CHECK: "-libpath:{{.*}}\\lib"
+! CHECK: "-libpath:{{.*}}\\lib\\clang\\{{[0-9]+}}\\lib\\windows"
diff --git a/clang/test/Driver/msvc-link.cpp b/clang/test/Driver/msvc-link.cpp
new file mode 100644
index 00000000000000..4d53fe49782e52
--- /dev/null
+++ b/clang/test/Driver/msvc-link.cpp
@@ -0,0 +1,7 @@
+// REQUIRES: system-windows
+//
+// RUN: %clang -### %s -Ltest 2>&1 | FileCheck %s
+//
+// Test that user provided paths come before compiler-rt
+// CHECK: "-libpath:test"
+// CHECK: "-libpath:{{.*}}\\lib\\clang\\{{[0-9]+}}\\lib\\windows"