[Driver] Search LibraryPaths when handling -print-file-name

[phosek]

Summary

This is necessary to handle the multiarch runtime directories.

[mcgrathr]

The log message could give concrete examples.

clang/lib/Driver/Driver.cpp

4169 ↗

(On Diff #163633)

A one-line comment before the lambda would help: // Check for Name in Path. (rename the param to be clearer)

4173 ↗

(On Diff #163633)

I'd always use const auto& in a range-for like this, but I guess this was just moved around and maybe LLVM style frowns on auto?

4179 ↗

(On Diff #163633)

Can this be return {P.str()};?

4184 ↗

(On Diff #163633)

I'd always use auto in these situations (here and below).

4187 ↗

(On Diff #163633)

You could fold these cases into the lambda too by having it take a bool UseSysRoot and passing {ResourceDir}, false.
Then the main body is a uniform and concise list of paths to check.

[phosek]

clang/lib/Driver/Driver.cpp

4187 ↗

(On Diff #163633)

I considered that but llvm::SmallVector doesn't support initializer list so this ends up looking not so great.

lib/Driver/Driver.cpp

else
       llvm::sys::path::append(BasePath, NamedOutput);
     return C.addResultFile(C.getArgs().MakeArgString(BasePath.c_str()), &JA);
   } else {
     return C.addResultFile(NamedOutput, &JA);
   }
 }
 
 std::string Driver::GetFilePath(StringRef Name, const ToolChain &TC) const {
+  // Seach for Name in a list of paths.
+  auto SearchPaths = [&](const llvm::SmallVectorImpl<std::string> &P)
+      -> llvm::Optional<std::string> {
     // Respect a limited subset of the '-Bprefix' functionality in GCC by
     // attempting to use this prefix when looking for file paths.
-  for (const std::string &Dir : PrefixDirs) {
+    for (const auto &Dir : P) {
       if (Dir.empty())
         continue;
       SmallString<128> P(Dir[0] == '=' ? SysRoot + Dir.substr(1) : Dir);
       llvm::sys::path::append(P, Name);
       if (llvm::sys::fs::exists(Twine(P)))
-      return P.str();
+        return {P.str()};
     }
+    return None;
+  };
+
+  if (auto P = SearchPaths(PrefixDirs))
+    return *P;
 
   SmallString<128> R(ResourceDir);
   llvm::sys::path::append(R, Name);
   if (llvm::sys::fs::exists(Twine(R)))
     return R.str();
 
   SmallString<128> P(TC.getCompilerRTPath());
   llvm::sys::path::append(P, Name);
   if (llvm::sys::fs::exists(Twine(P)))
     return P.str();
 
-  for (const std::string &Dir : TC.getFilePaths()) {
-    if (Dir.empty())
-      continue;
-    SmallString<128> P(Dir[0] == '=' ? SysRoot + Dir.substr(1) : Dir);
-    llvm::sys::path::append(P, Name);
-    if (llvm::sys::fs::exists(Twine(P)))
-      return P.str();
-  }
+  if (auto P = SearchPaths(TC.getLibraryPaths()))
+    return *P;
+
+  if (auto P = SearchPaths(TC.getFilePaths()))
+    return *P;
 
   return Name;
 }
 
 void Driver::generatePrefixedToolNames(
     StringRef Tool, const ToolChain &TC,
     SmallVectorImpl<std::string> &Names) const {
   // FIXME: Needs a better variable than TargetTriple

test/Driver/linux-per-target-runtime-dir.c

 // CHECK-PER-TARGET-RUNTIME: "--sysroot=[[SYSROOT]]"
 // CHECK-PER-TARGET-RUNTIME: "-L[[RESDIR]]{{/|\\\\}}x86_64-linux-gnu{{/|\\\\}}lib"
 
 // RUN: %clang -rtlib=compiler-rt -print-libgcc-file-name 2>&1 \
 // RUN:     --target=x86_64-linux-gnu \
 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
 // RUN:   | FileCheck --check-prefix=CHECK-CLANGRT-X8664 %s
 // CHECK-CLANGRT-X8664: x86_64-linux-gnu{{/|\\}}lib{{/|\\}}libclang_rt.builtins.a
+
+// RUN: %clang -rtlib=compiler-rt -print-file-name=libclang_rt.builtins.a 2>&1 \
+// RUN:     --target=x86_64-linux-gnu \
+// RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
+// RUN:   | FileCheck --check-prefix=CHECK-FILE-NAME-X8664 %s
+// CHECK-FILE-NAME-X8664: x86_64-linux-gnu{{/|\\}}lib{{/|\\}}libclang_rt.builtins.a