Revert D157750 "[Driver][CodeGen] Properly handle -fsplit-machine-fun…

…ctions for fatbinary compilation."

This reverts commit 317a0fe.
This reverts commit 30c4b97.

See post-commit discussions on https://reviews.llvm.org/D157750 that
we should use a different mechanism to handle the error with --cuda-gpu-arch=

The IR/DiagnosticInfo.cpp, warn_drv_for_elf_only, codegne tests in
clang/test/Driver, and the following driver behavior (downgrading error
to warning) changes are undesired.
```
% clang --target=riscv64 -fsplit-machine-functions -c a.c
warning: -fsplit-machine-functions is not valid for riscv64 [-Wbackend-plugin]
```

clang/include/clang/Basic/DiagnosticDriverKinds.td

@@ -693,10 +693,6 @@ def warn_drv_fjmc_for_elf_only : Warning<
   "-fjmc works only for ELF; option ignored">,
   InGroup<OptionIgnored>;
 
-def warn_drv_for_elf_only : Warning<
-  "'%0' works only for ELF; option ignored">,
-  InGroup<OptionIgnored>;
-
 def warn_target_override_arm64ec : Warning<
   "/arm64EC has been overridden by specified target: %0; option ignored">,
   InGroup<OptionIgnored>;

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5872,15 +5872,14 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
   if (Arg *A = Args.getLastArg(options::OPT_fsplit_machine_functions,
                                options::OPT_fno_split_machine_functions)) {
-    if (A->getOption().matches(options::OPT_fsplit_machine_functions)) {
-      // This codegen pass is only available on elf targets.
-      if (Triple.isOSBinFormatELF())
+    // This codegen pass is only available on x86-elf targets.
+    if (Triple.isX86() && Triple.isOSBinFormatELF()) {
+      if (A->getOption().matches(options::OPT_fsplit_machine_functions))
         A->render(Args, CmdArgs);
-      else
-        D.Diag(diag::warn_drv_for_elf_only) << A->getAsString(Args);
+    } else {
+      D.Diag(diag::err_drv_unsupported_opt_for_target)
+          << A->getAsString(Args) << TripleStr;
     }
-    // Do not issue warnings for -fno-split-machine-functions even it is not
-    // on ELF.
   }
 
   Args.AddLastArg(CmdArgs, options::OPT_finstrument_functions,

clang/test/Driver/fsplit-machine-functions.c

@@ -1,10 +1,10 @@
 // REQUIRES: arm-registered-target
 
-// RUN: %clang -### -target x86_64 -fprofile-use=default.profdata -fsplit-machine-functions %s -c -o %t.o 2>&1 | FileCheck -check-prefix=CHECK-OPT %s
-// RUN: %clang -### -target x86_64 -fsplit-machine-functions %s -c -o %t.o 2>&1 | FileCheck -check-prefix=CHECK-OPT %s
-// RUN: %clang -### -target x86_64 -fprofile-use=default.profdata -fsplit-machine-functions -fno-split-machine-functions %s -c -o %t.o 2>&1 | FileCheck -check-prefix=CHECK-NOOPT %s
-// RUN: %clang -c -target arm-unknown-linux-gnueabi -fsplit-machine-functions %s -o %t.o 2>&1 | FileCheck -check-prefix=CHECK-TRIPLE %s
+// RUN: %clang -### -target x86_64 -fprofile-use=default.profdata -fsplit-machine-functions %s -c 2>&1 | FileCheck -check-prefix=CHECK-OPT %s
+// RUN: %clang -### -target x86_64 -fsplit-machine-functions %s -c 2>&1 | FileCheck -check-prefix=CHECK-OPT %s
+// RUN: %clang -### -target x86_64 -fprofile-use=default.profdata -fsplit-machine-functions -fno-split-machine-functions %s -c 2>&1 | FileCheck -check-prefix=CHECK-NOOPT %s
+// RUN: not %clang -c -target arm-unknown-linux -fsplit-machine-functions %s 2>&1 | FileCheck -check-prefix=CHECK-TRIPLE %s
 
 // CHECK-OPT:       "-fsplit-machine-functions"
 // CHECK-NOOPT-NOT: "-fsplit-machine-functions"
-// CHECK-TRIPLE:    warning: -fsplit-machine-functions is not valid for arm
+// CHECK-TRIPLE:    error: unsupported option '-fsplit-machine-functions' for target

clang/test/Driver/fsplit-machine-functions2.c

@@ -1,15 +1,12 @@
 // Test -fsplit-machine-functions option pass-through with lto
-// RUN: %clang -### -target x86_64-unknown-linux -flto -fsplit-machine-functions %s -o %t.o 2>&1 | FileCheck %s -check-prefix=CHECK-PASS
+// RUN: %clang -### -target x86_64-unknown-linux -flto -fsplit-machine-functions %s 2>&1 | FileCheck %s -check-prefix=CHECK-PASS
 
 // Test no pass-through to ld without lto
-// RUN: %clang -### -target x86_64-unknown-linux -fsplit-machine-functions %s -o %t.o 2>&1 | FileCheck %s -check-prefix=CHECK-NOPASS
+// RUN: %clang -### -target x86_64-unknown-linux -fsplit-machine-functions %s 2>&1 | FileCheck %s -check-prefix=CHECK-NOPASS
 
 // Test the mix of -fsplit-machine-functions and -fno-split-machine-functions
-// RUN: %clang -### -target x86_64-unknown-linux -flto -fsplit-machine-functions -fno-split-machine-functions %s -o %t.o 2>&1 | FileCheck %s -check-prefix=CHECK-NOPASS
-// RUN: %clang -### -target x86_64-unknown-linux -flto -fno-split-machine-functions -fsplit-machine-functions %s -o %t.o 2>&1 | FileCheck %s -check-prefix=CHECK-PASS
-// Check that for non-X86, passing no-split-machine-functions does not cause error.
-// RUN: %clang -### -target aarch64-unknown-linux-gnu -flto -fsplit-machine-functions -fno-split-machine-functions %s -o %t.o 2>&1 | FileCheck %s -check-prefix=CHECK-NOPASS2
+// RUN: %clang -### -target x86_64-unknown-linux -flto -fsplit-machine-functions -fno-split-machine-functions %s 2>&1 | FileCheck %s -check-prefix=CHECK-NOPASS
+// RUN: %clang -### -target x86_64-unknown-linux -flto -fno-split-machine-functions -fsplit-machine-functions %s 2>&1 | FileCheck %s -check-prefix=CHECK-PASS
 
 // CHECK-PASS:          "-plugin-opt=-split-machine-functions"
 // CHECK-NOPASS-NOT:    "-plugin-opt=-split-machine-functions"
-// CHECK-NOPASS2-NOT:   "-plugin-opt=-split-machine-functions"

llvm/include/llvm/IR/DiagnosticInfo.h

@@ -86,7 +86,6 @@ enum DiagnosticKind {
   DK_SrcMgr,
   DK_DontCall,
   DK_MisExpect,
-  DK_MachineFunctionSplit,
   DK_FirstPluginKind // Must be last value to work with
                      // getNextAvailablePluginDiagnosticKind
 };
@@ -1118,20 +1117,6 @@ class DiagnosticInfoDontCall : public DiagnosticInfo {
   }
 };
 
-class DiagnosticInfoMachineFunctionSplit : public DiagnosticInfo {
-  StringRef TargetTriple;
-
-public:
-  DiagnosticInfoMachineFunctionSplit(StringRef TargetTriple,
-                                     DiagnosticSeverity DS)
-      : DiagnosticInfo(DK_MachineFunctionSplit, DS),
-        TargetTriple(TargetTriple) {}
-  void print(DiagnosticPrinter &DP) const override;
-  static bool classof(const DiagnosticInfo *DI) {
-    return DI->getKind() == DK_MachineFunctionSplit;
-  }
-};
-
 } // end namespace llvm
 
 #endif // LLVM_IR_DIAGNOSTICINFO_H

llvm/lib/CodeGen/MachineFunctionSplitter.cpp

@@ -35,11 +35,9 @@
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/Passes.h"
-#include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/Function.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Support/CommandLine.h"
-#include "llvm/TargetParser/Triple.h"
 #include <optional>
 
 using namespace llvm;
@@ -84,13 +82,6 @@ class MachineFunctionSplitter : public MachineFunctionPass {
   void getAnalysisUsage(AnalysisUsage &AU) const override;
 
   bool runOnMachineFunction(MachineFunction &F) override;
-
-  bool doInitialization(Module &) override;
-
-  static bool isSupportedTriple(const Triple &T) { return T.isX86(); }
-
-private:
-  bool UnsupportedTriple = false;
 };
 } // end anonymous namespace
 
@@ -136,20 +127,7 @@ static bool isColdBlock(const MachineBasicBlock &MBB,
   return (*Count < ColdCountThreshold);
 }
 
-bool MachineFunctionSplitter::doInitialization(Module &M) {
-  StringRef T = M.getTargetTriple();
-  if (!isSupportedTriple(Triple(T))) {
-    UnsupportedTriple = true;
-    M.getContext().diagnose(
-        DiagnosticInfoMachineFunctionSplit(T, DS_Warning));
-    return false;
-  }
-  return MachineFunctionPass::doInitialization(M);
-}
-
 bool MachineFunctionSplitter::runOnMachineFunction(MachineFunction &MF) {
-  if (UnsupportedTriple)
-    return false;
   // We target functions with profile data. Static information in the form
   // of exception handling code may be split to cold if user passes the
   // mfs-split-ehcode flag.

llvm/lib/IR/DiagnosticInfo.cpp

@@ -449,7 +449,3 @@ void DiagnosticInfoDontCall::print(DiagnosticPrinter &DP) const {
   if (!getNote().empty())
     DP << ": " << getNote();
 }
-
-void DiagnosticInfoMachineFunctionSplit::print(DiagnosticPrinter &DP) const {
-  DP << "-fsplit-machine-functions is not valid for " << TargetTriple;
-}

llvm/test/CodeGen/Generic/machine-function-splitter.ll

@@ -11,15 +11,6 @@
 ; RUN: sed 's/InstrProf/SampleProfile/g' %s > %t.ll
 ; RUN: llc < %t.ll -mtriple=x86_64-unknown-linux-gnu -split-machine-functions | FileCheck %s --check-prefix=FSAFDO-MFS
 ; RUN: llc < %t.ll -mtriple=x86_64-unknown-linux-gnu -split-machine-functions | FileCheck %s --check-prefix=FSAFDO-MFS2
-; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -debug-pass=Structure -fs-profile-file=%S/Inputs/fsloader-mfs.afdo -enable-fs-discriminator=true -improved-fs-discriminator=true -split-machine-functions 2>&1 | FileCheck %s --check-prefix=MFS_ON
-; RUN: llc < %s -mtriple=aarch64-unknown-linux-gnu -debug-pass=Structure -fs-profile-file=%S/Inputs/fsloader-mfs.afdo -enable-fs-discriminator=true -improved-fs-discriminator=true -split-machine-functions 2>&1 | FileCheck %s --check-prefix=MFS_OFF
-
-;; Check that MFS is on for X86 targets.
-; MFS_ON: Machine Function Splitter Transformation
-; MFS_ON_NO: warning: -fsplit-machine-functions is not valid for
-;; Check that MFS is not on for non-X86 targets.
-; MFS_OFF: warning: -fsplit-machine-functions is not valid for
-; MFS_OFF_NO: Machine Function Splitter Transformation
 
 define void @foo1(i1 zeroext %0) nounwind !prof !14 !section_prefix !15 {
 ;; Check that cold block is moved to .text.split.