[Remarks][Driver] Use different remark files when targeting multiple architectures

When the driver is targeting multiple architectures at once, for things
like Universal Mach-Os, we need to emit different remark files for each
cc1 invocation to avoid overwriting the files from a different
invocation.

For example:

$ clang -c -o foo.o -fsave-optimization-record -arch x86_64 -arch x86_64h

will create two remark files:

* foo-x86_64.opt.yaml
* foo-x86_64h.opt.yaml

1 files changed, 18 insertions, 0 deletions

diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 2b1c24275e3..f5591c48d4e 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5403,6 +5403,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     if (A) {
       CmdArgs.push_back(A->getValue());
     } else {
+      bool hasMultipleArchs =
+          Args.getAllArgValues(options::OPT_arch).size() > 1;
       SmallString<128> F;
 
       if (Args.hasArg(options::OPT_c) || Args.hasArg(options::OPT_S)) {
@@ -5427,6 +5429,22 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
         }
       }
 
+      // If we're having more than one "-arch", we should name the files
+      // differently so that every cc1 invocation writes to a different file.
+      // We're doing that by appending "-<arch>" with "<arch>" being the arch
+      // name from the triple.
+      if (hasMultipleArchs) {
+        // First, remember the extension.
+        SmallString<64> OldExtension = llvm::sys::path::extension(F);
+        // then, remove it.
+        llvm::sys::path::replace_extension(F, "");
+        // attach -<arch> to it.
+        F += "-";
+        F += Triple.getArchName();
+        // put back the extension.
+        llvm::sys::path::replace_extension(F, OldExtension);
+      }
+
       std::string Extension = "opt.";
       if (const Arg *A =
               Args.getLastArg(options::OPT_fsave_optimization_record_EQ))