[Driver] Add -fsample-profile-use-profi

This patch enable `-sample-profile-use-profi` in Clang frontend as user-facing
feature. By using this patch, we can use the cflag of `-fsample-profile-use-profi`
instead of `-mllvm -sample-profile-use-profi`.

Reviewed By: hans, MaskRay

Differential Revision: https://reviews.llvm.org/D136846

Author: haoyuintel

clang/docs/UsersManual.rst

@@ -2241,6 +2241,15 @@ usual build cycle when using sample profilers for optimization:
 
      $ clang++ -O2 -gline-tables-only -fprofile-sample-use=code.prof code.cc -o code
 
+  [OPTIONAL] Sampling-based profiles can have inaccuracies or missing block/
+  edge counters. The profile inference algorithm (profi) can be used to infer
+  missing blocks and edge counts, and improve the quality of profile data.
+  Enable it with ``-fsample-profile-use-profi``.
+
+  .. code-block:: console
+
+    $ clang++ -O2 -gline-tables-only -fprofile-sample-use=code.prof \
+      -fsample-profile-use-profi code.cc -o code
 
 Sample Profile Formats
 """"""""""""""""""""""

clang/include/clang/Driver/Options.td

@@ -1251,6 +1251,13 @@ def fprofile_sample_accurate : Flag<["-"], "fprofile-sample-accurate">,
                as cold. Otherwise, treat callsites without profile samples as if
                we have no profile}]>,
    MarshallingInfoFlag<CodeGenOpts<"ProfileSampleAccurate">>;
+def fsample_profile_use_profi : Flag<["-"], "fsample-profile-use-profi">,
+    Flags<[NoXarchOption, CC1Option]>, Group<f_Group>,
+    HelpText<"Use profi to infer block and edge counts">,
+    DocBrief<[{Infer block and edge counts. If the profiles have errors or missing
+               blocks caused by sampling, profile inference (profi) can convert
+               basic block counts to branch probabilites to fix them by extended
+               and re-engineered classic MCMF (min-cost max-flow) approach.}]>;
 def fno_profile_sample_accurate : Flag<["-"], "fno-profile-sample-accurate">,
   Group<f_Group>, Flags<[NoXarchOption]>;
 def fauto_profile : Flag<["-"], "fauto-profile">, Group<f_Group>,

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5729,6 +5729,12 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
   Args.AddLastArg(CmdArgs, options::OPT_fclang_abi_compat_EQ);
 
+  if (getLastProfileSampleUseArg(Args) &&
+      Args.hasArg(options::OPT_fsample_profile_use_profi)) {
+    CmdArgs.push_back("-mllvm");
+    CmdArgs.push_back("-sample-profile-use-profi");
+  }
+
   // Add runtime flag for PS4/PS5 when PGO, coverage, or sanitizers are enabled.
   if (RawTriple.isPS() &&
       !Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {

clang/test/Driver/pgo-sample-use-profi.c

@@ -0,0 +1,4 @@
+/// Test if profi flat is enabled in frontend as user-facing feature.
+// RUN: %clang -c -fsample-profile-use-profi -fprofile-sample-use=/dev/null -### %s 2>&1 | FileCheck %s
+
+// CHECK: "-mllvm" "-sample-profile-use-profi"