Revert "[CodeGen] Fix unconditional branch duplication issue in bbsections"

This reverts commit 994eb5a.
Breaks buildbot `llvm-clang-x86_64-expensive-checks-debian`
https://lab.llvm.org/buildbot/#/builders/16/builds/53620

Author: dhoekwater

llvm/lib/CodeGen/BasicBlockSections.cpp

@@ -258,8 +258,7 @@ void llvm::sortBasicBlocksAndUpdateBranches(
   [[maybe_unused]] const MachineBasicBlock *EntryBlock = &MF.front();
   SmallVector<MachineBasicBlock *> PreLayoutFallThroughs(MF.getNumBlockIDs());
   for (auto &MBB : MF)
-    PreLayoutFallThroughs[MBB.getNumber()] =
-        MBB.getFallThrough(/*JumpToFallThrough=*/false);
+    PreLayoutFallThroughs[MBB.getNumber()] = MBB.getFallThrough();
 
   MF.sort(MBBCmp);
   assert(&MF.front() == EntryBlock &&

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

@@ -6,13 +6,11 @@
 ; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -split-machine-functions -mfs-psi-cutoff=0 -mfs-count-threshold=2000 | FileCheck %s --dump-input=always -check-prefixes=MFS-OPTS1,MFS-OPTS1-X86
 ; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -split-machine-functions -mfs-psi-cutoff=950000 | FileCheck %s -check-prefixes=MFS-OPTS2,MFS-OPTS2-X86
 ; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -split-machine-functions -mfs-split-ehcode | FileCheck %s -check-prefixes=MFS-EH-SPLIT,MFS-EH-SPLIT-X86
-; RUN: llc < %s -mtriple=x86_64 -split-machine-functions -O0 -mfs-psi-cutoff=0 -mfs-count-threshold=10000 | FileCheck %s -check-prefixes=MFS-O0,MFS-O0-X86
 
 ; RUN: llc < %s -mtriple=aarch64-unknown-linux-gnu -enable-split-machine-functions -mfs-allow-unsupported-triple | FileCheck %s -check-prefixes=MFS-DEFAULTS,MFS-DEFAULTS-AARCH64
 ; RUN: llc < %s -mtriple=aarch64-unknown-linux-gnu -enable-split-machine-functions -mfs-allow-unsupported-triple -mfs-psi-cutoff=0 -mfs-count-threshold=2000 | FileCheck %s --dump-input=always -check-prefixes=MFS-OPTS1,MFS-OPTS1-AARCH64
 ; RUN: llc < %s -mtriple=aarch64-unknown-linux-gnu -enable-split-machine-functions -mfs-allow-unsupported-triple -mfs-psi-cutoff=950000 | FileCheck %s -check-prefixes=MFS-OPTS2,MFS-OPTS2-AARCH64
 ; RUN: llc < %s -mtriple=aarch64-unknown-linux-gnu -enable-split-machine-functions -mfs-allow-unsupported-triple -mfs-split-ehcode | FileCheck %s -check-prefixes=MFS-EH-SPLIT,MFS-EH-SPLIT-AARCH64
-; RUN: llc < %s -mtriple=aarch64 -enable-split-machine-functions -O0 -mfs-allow-unsupported-triple -mfs-psi-cutoff=0 -mfs-count-threshold=10000 | FileCheck %s --dump-input=always -check-prefixes=MFS-O0,MFS-O0-AARCH64
 
 ; COM: Machine function splitting with AFDO profiles
 ; RUN: sed 's/InstrProf/SampleProfile/g' %s > %t.ll
@@ -464,29 +462,6 @@ define void @foo15(i1 zeroext %0, i1 zeroext %1) nounwind !prof !27 {
   ret void
 }
 
-define void @foo16(i1 zeroext %0) nounwind !prof !14 !section_prefix !15 {
-;; Check that an unconditional branch is only appended to a block
-;; if it would fall through to the wrong block otherwise.
-; MFS-O0-LABEL:               foo16
-; MFS-O0-X86:                 jmp
-; MFS-O0-X86-NOT:             jmp
-; MFS-O0-AARCH64:                 br
-; MFS-O0-AARCH64:                 br
-; MFS-O0-AARCH64-NOT:             br
-; MFS-O0:                     .section        .text.split.foo16
-; MFS-O0-NEXT:                foo16.cold
-  %2 = call i32 @baz()
-  br i1 false, label %3, label %5, !prof !25
-
-3:                                                ; preds = %1
-  %4 = call i32 @bar()
-  unreachable
-
-5:                                                ; preds = %1
-  %6 = tail call i32 @qux()
-  ret void
-}
-
 declare i32 @bar()
 declare i32 @baz()
 declare i32 @bam()