[clang] [Clang][Driver][LTO] Fix empty stats filename when in LTO mode (PR #71197)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-driver

@llvm/pr-subscribers-clang

Author: Min-Yih Hsu (mshockwave)

<details>
<summary>Changes</summary>

Previously, if a linker flag (i.e. -Wl) is presented before any input filenames, Gnu driver would use the InputInfo object of that flag to generate stats filename for LTO backend, causing an empty filename. This patch fixes such issue.

---
Full diff: https://github.com/llvm/llvm-project/pull/71197.diff


2 Files Affected:

- (modified) clang/lib/Driver/ToolChains/Gnu.cpp (+9-1) 
- (modified) clang/test/Driver/save-stats.c (+2) 


``````````diff
diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index 5237951f84cce03..8448d4bda13c434 100644
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -535,7 +535,15 @@ void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
 
   if (D.isUsingLTO()) {
     assert(!Inputs.empty() && "Must have at least one input.");
-    addLTOOptions(ToolChain, Args, CmdArgs, Output, Inputs[0],
+    // Find the first filename InputInfo object.
+    auto Input = llvm::find_if(
+        Inputs, [](const InputInfo &II) -> bool { return II.isFilename(); });
+    if (Input == Inputs.end())
+      // For a very rare case, all of the inputs to the linker are
+      // flags. If that happens, just use the first InputInfo.
+      Input = Inputs.begin();
+
+    addLTOOptions(ToolChain, Args, CmdArgs, Output, *Input,
                   D.getLTOMode() == LTOK_Thin);
   }
 
diff --git a/clang/test/Driver/save-stats.c b/clang/test/Driver/save-stats.c
index ca8f2a457d4488c..d6ad4e0097f3432 100644
--- a/clang/test/Driver/save-stats.c
+++ b/clang/test/Driver/save-stats.c
@@ -20,6 +20,8 @@
 // CHECK-INVALID: invalid value 'bla' in '-save-stats=bla'
 
 // RUN: %clang -target x86_64-linux-unknown -save-stats -flto -o obj/dir/save-stats.exe %s -### 2>&1 | FileCheck %s -check-prefix=CHECK-LTO
+// Previously `-plugin-opt=stats-file` would use empty filename if a linker flag (i.e. -Wl) is presented before any input filename.
+// RUN: %clang -target x86_64-linux-unknown -save-stats -flto -o obj/dir/save-stats.exe -Wl,-plugin-opt=-dummy %s -### 2>&1 | FileCheck %s -check-prefix=CHECK-LTO
 // CHECK-LTO: "-stats-file=save-stats.stats"
 // CHECK-LTO: "-o" "obj/dir{{/|\\\\}}save-stats.exe"
 // CHECK-LTO: "-plugin-opt=stats-file=save-stats.stats"

``````````

</details>


https://github.com/llvm/llvm-project/pull/71197