Reland: [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

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5218,6 +5218,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     if (A) {
       CmdArgs.push_back(A->getValue());
     } else {
+      bool hasMultipleArchs =
+          Triple.isOSDarwin() && // Only supported on Darwin platforms.
+          Args.getAllArgValues(options::OPT_arch).size() > 1;
       SmallString<128> F;
 
       if (Args.hasArg(options::OPT_c) || Args.hasArg(options::OPT_S)) {
@@ -5242,6 +5245,22 @@ 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))

clang/test/Driver/darwin-opt-record.c

@@ -0,0 +1,8 @@
+// REQUIRES: system-darwin
+
+// RUN: %clang -### -S -o FOO -fsave-optimization-record -arch x86_64 -arch x86_64h %s 2>&1 | FileCheck %s --check-prefix=CHECK-MULTIPLE-ARCH
+//
+// CHECK-MULTIPLE-ARCH: "-cc1"
+// CHECK-MULTIPLE-ARCH: "-opt-record-file" "FOO-x86_64.opt.yaml"
+// CHECK-MULTIPLE-ARCH: "-cc1"
+// CHECK-MULTIPLE-ARCH: "-opt-record-file" "FOO-x86_64h.opt.yaml"