[Profile]: make 'no profile data' warning off by default

[davidxl]

Summary

With any large project, it is very common that many modules in static archive never get linked in the the final instrumented executable, thus functions defined in those modules won't have profile data collected. As a result, during profile-use compilation, we will end up getting tons of 'no profile data available for function ...' warnings which is not useful at all. A better way to handle this is to enhance profile runtime to record the modules that are linked in (at the cost of slightly increased profile size)

This patch makes the emission of such warnings off by default.

[silvas]

LGTM.

I think this is the last item from "The state of IRPGO (3 remaining work items)"! Thanks!

llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp

 // function. This is to avoid the hash mismatch caused by the preinliner.
 static cl::opt<bool> DoComdatRenaming(
     "do-comdat-renaming", cl::init(true), cl::Hidden,
     cl::desc("Append function hash to the name of COMDAT function to avoid "
              "function hash mismatch due to the preinliner"));
 
 // Command line option to enable/disable the warning about missing profile
 // information.
-static cl::opt<bool> NoPGOWarnMissing("no-pgo-warn-missing", cl::init(false),
+static cl::opt<bool> NoPGOWarnMissing("no-pgo-warn-missing", cl::init(true),
                                       cl::Hidden);
 
 // Command line option to enable/disable the warning about a hash mismatch in
 // the profile data.
 static cl::opt<bool> NoPGOWarnMismatch("no-pgo-warn-mismatch", cl::init(false),
                                        cl::Hidden);
 
 namespace {

llvm/trunk/test/Transforms/PGOProfile/diag_no_funcprofdata.ll

 ; RUN: llvm-profdata merge %S/Inputs/diag.proftext -o %t.profdata
-; RUN: opt < %s -pgo-instr-use -pgo-test-profile-file=%t.profdata -S 2>&1 | FileCheck %s
-; RUN: opt < %s -passes=pgo-instr-use -pgo-test-profile-file=%t.profdata -S 2>&1 | FileCheck %s
+; RUN: opt < %s -pgo-instr-use -no-pgo-warn-missing=false -pgo-test-profile-file=%t.profdata -S 2>&1 | FileCheck %s
+; RUN: opt < %s -passes=pgo-instr-use -no-pgo-warn-missing=false -pgo-test-profile-file=%t.profdata -S 2>&1 | FileCheck %s
 
 ; CHECK: No profile data available for function bar
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 define i32 @bar() {
 entry:
   ret i32 0 
 }