[llvm-profdata] Enabled functionality to write split-layout profile

Using the flag `-split_layout` in llvm-profdata merge, the output
profile can write profiles with and without inlined function into two
different extbinary sections (and their FuncOffsetTable too). The
section without inlined functions are marked with `SecFlagFlat` and is
skipped by ThinLTO because it provides no useful info.

The split layout feature was already implemented in SampleProfWriter but previously
there is no way from the tool to use it.

Author: huangjd

llvm/docs/CommandGuide/llvm-profdata.rst

@@ -162,6 +162,12 @@ OPTIONS
  coverage for the optimized target. This option can only be used with
  sample-based profile in extbinary format.
 
+.. option:: --split_layout=[true|false]
+
+ Split the profile data section to two with one containing sample profiles with
+ inlined functions and the other not. This option can only be used with
+ sample-based profile in extbinary format.
+
 .. option:: --convert-sample-profile-layout=[nest|flat]
 
  Convert the merged profile into a profile with a new layout. Supported

llvm/test/tools/llvm-profdata/Inputs/split-layout.profdata

@@ -0,0 +1,2 @@
+RUN: llvm-profdata merge --sample --extbinary --split_layout %p/Inputs/sample-profile.proftext -o %t-output
+RUN: diff %t-output %p/Inputs/split-layout.profdata

llvm/test/tools/llvm-profdata/sample-split-layout.test

@@ -207,6 +207,12 @@ cl::opt<bool> GenPartialProfile(
     "gen-partial-profile", cl::init(false), cl::Hidden,
     cl::sub(MergeSubcommand),
     cl::desc("Generate a partial profile (only meaningful for -extbinary)"));
+cl::opt<bool> SplitLayout(
+    "split_layout", cl::init(false), cl::Hidden,
+    cl::sub(MergeSubcommand),
+    cl::desc("Split the profile to two sections with one containing sample "
+             "profiles with inlined functions and the another not (only "
+             "meaningful for -extbinary)"));
 cl::opt<std::string> SupplInstrWithSample(
     "supplement-instr-with-sample", cl::init(""), cl::Hidden,
     cl::sub(MergeSubcommand),
@@ -1492,6 +1498,12 @@ static void handleExtBinaryWriter(sampleprof::SampleProfileWriter &Writer,
     else
       Writer.setPartialProfile();
   }
+  if (SplitLayout) {
+    if (OutputFormat != PF_Ext_Binary)
+      warn("-split-layout is ignored. Specify -extbinary to enable it");
+    else
+      Writer.resetSecLayout(SectionLayout::CtxSplitLayout);
+  }
 }
 
 static void mergeSampleProfile(const WeightedFileVector &Inputs,