Basic Block Sections support in LLVM.

This is the second patch in a series of patches to enable basic block
sections support.

This patch adds support for:

* Creating direct jumps at the end of basic blocks that have fall
through instructions.
* New pass, bbsections-prepare, that analyzes placement of basic blocks
in sections.
* Actual placing of a basic block in a unique section with special
handling of exception handling blocks.
* Supports placing a subset of basic blocks in a unique section.
* Support for MIR serialization and deserialization with basic block
sections.

Parent patch : D68063
Differential Revision: https://reviews.llvm.org/D73674

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/Target/TargetLoweringObjectFile.cpp b/llvm/lib/Target/TargetLoweringObjectFile.cpp
index cfdb675..9f464c0 100644
--- a/llvm/lib/Target/TargetLoweringObjectFile.cpp
+++ b/llvm/lib/Target/TargetLoweringObjectFile.cpp
@@ -149,6 +149,10 @@ SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalObject *GO,
   if (isa<Function>(GO))
     return SectionKind::getText();
 
+  // Basic blocks are classified as text sections.
+  if (isa<BasicBlock>(GO))
+    return SectionKind::getText();
+
   // Global variables require more detailed analysis.
   const auto *GVar = cast<GlobalVariable>(GO);
 
@@ -302,6 +306,18 @@ MCSection *TargetLoweringObjectFile::getSectionForConstant(
   return DataSection;
 }
 
+MCSection *TargetLoweringObjectFile::getSectionForMachineBasicBlock(
+    const Function &F, const MachineBasicBlock &MBB,
+    const TargetMachine &TM) const {
+  return nullptr;
+}
+
+MCSection *TargetLoweringObjectFile::getNamedSectionForMachineBasicBlock(
+    const Function &F, const MachineBasicBlock &MBB, const TargetMachine &TM,
+    const char *Suffix) const {
+  return nullptr;
+}
+
 /// getTTypeGlobalReference - Return an MCExpr to use for a
 /// reference to the specified global variable from exception
 /// handling information.