[LTO] Add --lto-pgo-warn-mismatch support for legacy PM

[MaskRay]

I struggled a bit whether --lto-pgo-warn-mismatch should be added as an option and was happy with other reviewers adding it.
(IMHO others don't feel there is a strong need for the option as well.)

Now there is probably very little value adding it for the legacy PM which is being deleted.

[zsrkmyn]

I'm OK not merging this.

lld/test/COFF/pgo-warn-mismatch.ll

 ; REQUIRES: x86
 
 ; RUN: rm -rf %t && split-file %s %t
 ; RUN: opt -module-summary %t/a.ll -o %t/a.bc
 ; RUN: llvm-profdata merge %t/cs.proftext -o %t/cs.profdata
 
 ; Ensure lld generates warnings for profile cfg mismatch.
 ; RUN: lld-link /dll /noentry /export:f /lto-cs-profile-file:%t/cs.profdata /lto-pgo-warn-mismatch /opt:lldlto=2 %t/a.bc /out:%t/a.dll 2>&1 | FileCheck %s
+; RUN: lld-link /lto-legacy-pass-manager:no /dll /noentry /export:f /lto-cs-profile-file:%t/cs.profdata /lto-pgo-warn-mismatch /opt:lldlto=2 %t/a.bc /out:%t/a.dll 2>&1 | FileCheck %s
 
 ; Ensure lld will not generate warnings for profile cfg mismatch.
 ; RUN: lld-link /dll /noentry /export:f /lto-cs-profile-file:%t/cs.profdata /lto-pgo-warn-mismatch:no /opt:lldlto=2 %t/a.bc /out:%t/a.dll 2>&1 | count 0
+; RUN: lld-link /lto-legacy-pass-manager:no /dll /noentry /export:f /lto-cs-profile-file:%t/cs.profdata /lto-pgo-warn-mismatch:no /opt:lldlto=2 %t/a.bc /out:%t/a.dll 2>&1 | count 0
 
 ; CHECK: warning: {{.*}} function control flow change detected (hash mismatch) f Hash = [[#]]
 
 ;--- a.ll
 target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-pc-windows-msvc"
 
 define i32 @f(i32 returned %a) #0 {

lld/test/ELF/lto/pgo-warn-mismatch.ll

 ; REQUIRES: x86
 
 ; RUN: rm -rf %t && split-file %s %t
 ; RUN: opt -module-summary %t/a.ll -o %t/a.bc
 ; RUN: llvm-profdata merge %t/cs.proftext -o %t/cs.profdata
 
 ;; Ensure lld generates warnings for profile cfg mismatch.
 ; RUN: ld.lld --lto-cs-profile-file=%t/cs.profdata --lto-pgo-warn-mismatch -shared %t/a.bc -o /dev/null 2>&1 | FileCheck %s
+; RUN: ld.lld --no-lto-legacy-pass-manager --lto-cs-profile-file=%t/cs.profdata --lto-pgo-warn-mismatch -shared %t/a.bc -o /dev/null 2>&1 | FileCheck %s
 
 ;; Ensure lld will not generate warnings for profile cfg mismatch.
 ; RUN: ld.lld --lto-cs-profile-file=%t/cs.profdata --no-lto-pgo-warn-mismatch -shared --fatal-warnings %t/a.bc -o /dev/null
+; RUN: ld.lld --no-lto-legacy-pass-manager --lto-cs-profile-file=%t/cs.profdata --no-lto-pgo-warn-mismatch -shared --fatal-warnings %t/a.bc -o /dev/null
 
 ; CHECK: warning: {{.*}} function control flow change detected (hash mismatch) f Hash = [[#]]
 
 ;--- a.ll
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 define i32 @f(i32 returned %a) #0 {

llvm/lib/LTO/LTOBackend.cpp

 }
 
 static void runOldPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
                            bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
                            const ModuleSummaryIndex *ImportSummary) {
   legacy::PassManager passes;
   passes.add(createTargetTransformInfoWrapperPass(TM->getTargetIRAnalysis()));
 
+  NoPGOWarnMismatch = !Conf.PGOWarnMismatch;
+
   PassManagerBuilder PMB;
   PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM->getTargetTriple()));
   if (Conf.Freestanding)
     PMB.LibraryInfo->disableAllFunctions();
   PMB.Inliner = createFunctionInliningPass();
   PMB.ExportSummary = ExportSummary;
   PMB.ImportSummary = ImportSummary;
   // Unconditionally verify input since it is not verified before this