[Comgr] Create new SAVE_TEMPS env var for Clang Driver temps (llvm#612)

Forwarding '--save-temps=obj' to the Clang Driver and generating the
associated temps slightly changes the behavior of the compilation. For
example, the compilation may be broken up into several steps to generate
the intermediate files.

In many cases, a user may only want the Comgr temps without modifying
the compilation behavior. To enable this, we introduce a new Comgr
environment variable:

  AMD_COMGR_SAVE_LLVM_TEMPS

With this change, '--save-temps=obj' is only forwarded if the above is
set to non-zero. And AMD_COMGR_SAVE_TEMPS now only saves Comgr temps.

Author: lamb-j

amd/comgr/README.md

@@ -122,6 +122,8 @@ include:
   the current working directory, but are instead left in a platform-specific
   temporary directory (typically `/tmp` on Linux and `C:\Temp` or the path
   found in the `TEMP` environment variable on Windows).
+* `AMD_COMGR_SAVE_LLVM_TEMPS`: If this is set, Comgr forwards `--save-temps=obj`
+  to Clang Driver invocations.
 * `AMD_COMGR_REDIRECT_LOGS`: If this is not set, or is set to "0", logs are
   returned to the caller as normal. If this is set to "stdout"/"-" or "stderr",
   logs are instead redirected to the standard output or error stream,

amd/comgr/include/amd_comgr.h.in

@@ -148,6 +148,8 @@ extern "C" {
  *   These files do not appear in the current working directory, but are
  *   instead left in a platform-specific temporary directory (/tmp on Linux and
  *   C:\Temp or the path found in the TEMP environment variable on Windows).
+ * - @p AMD_COMGR_SAVE_LLVM_TEMPS: If this is set, and is not "0", Comgr
+ *   forwards "--save-temps=obj" to Clang Driver invocations
  * - @p AMD_COMGR_REDIRECT_LOGS: If this is not set, or is set to "0", logs are
  *   returned to the caller as normal. If this is set to "stdout"/"-" or
  *   "stderr", logs are instead redirected to the standard output or error

amd/comgr/src/comgr-compiler.cpp

@@ -878,7 +878,8 @@ amd_comgr_status_t AMDGPUCompiler::processFile(const char *InputFilePath,
     Argv.push_back("-nogpulib");
   }
 
-  if (getLanguage() == AMD_COMGR_LANGUAGE_HIP && env::shouldSaveTemps()) {
+  // TODO: Enable this for OpenCL as well (SWDEV-377546)
+  if (getLanguage() == AMD_COMGR_LANGUAGE_HIP && env::shouldSaveLLVMTemps()) {
     Argv.push_back("-save-temps=obj");
   }
 

amd/comgr/src/comgr-env.cpp

@@ -51,6 +51,11 @@ bool shouldSaveTemps() {
   return SaveTemps && StringRef(SaveTemps) != "0";
 }
 
+bool shouldSaveLLVMTemps() {
+  static char *SaveTemps = getenv("AMD_COMGR_SAVE_LLVM_TEMPS");
+  return SaveTemps && StringRef(SaveTemps) != "0";
+}
+
 std::optional<StringRef> getRedirectLogs() {
   static char *RedirectLogs = getenv("AMD_COMGR_REDIRECT_LOGS");
   if (!RedirectLogs || StringRef(RedirectLogs) == "0") {

amd/comgr/src/comgr-env.h

@@ -43,6 +43,7 @@ namespace env {
 
 /// Return whether the environment requests temps be saved.
 bool shouldSaveTemps();
+bool shouldSaveLLVMTemps();
 
 /// If the environment requests logs be redirected, return the string identifier
 /// of where to redirect. Otherwise return @p None.