[PATCH] D131863: [CodeGen] Fix restore blocks' BasicBlock information in branch relaxation

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In branch relaxation pass, restore blocks are created and placed before the jump destination if indirect branches are required. For example:

          foo
          sd      s11, 0(sp)
          jump    .restore, s11
          bar
          bar
          bar
          j       .dest
  .restore:
          ld      s11, 0(sp)
  .dest:
          baz

The BasicBlock information of the restore MachineBasicBlock should be identical to the dest MachineBasicBlock.

Depends on D131862 <https://reviews.llvm.org/D131862>, which pre-commits the modified test.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D131863

Files:
  llvm/lib/CodeGen/BranchRelaxation.cpp
  llvm/test/CodeGen/RISCV/branch-relaxation.ll


Index: llvm/test/CodeGen/RISCV/branch-relaxation.ll
===================================================================
--- llvm/test/CodeGen/RISCV/branch-relaxation.ll
+++ llvm/test/CodeGen/RISCV/branch-relaxation.ll
@@ -1430,14 +1430,14 @@
 ; CHECK-RV32-NEXT:    .zero 1048576
 ; CHECK-RV32-NEXT:    #NO_APP
 ; CHECK-RV32-NEXT:    j .LBB6_4
-; CHECK-RV32-NEXT:  .LBB6_8: # %dest_3
+; CHECK-RV32-NEXT:  .LBB6_8: # %dest_1
 ; CHECK-RV32-NEXT:    lw s11, 0(sp)
 ; CHECK-RV32-NEXT:  .LBB6_4: # %dest_1
 ; CHECK-RV32-NEXT:    #APP
 ; CHECK-RV32-NEXT:    # dest 1
 ; CHECK-RV32-NEXT:    #NO_APP
 ; CHECK-RV32-NEXT:    j .LBB6_5
-; CHECK-RV32-NEXT:  .LBB6_10: # %dest_3
+; CHECK-RV32-NEXT:  .LBB6_10: # %dest_2
 ; CHECK-RV32-NEXT:    lw s11, 0(sp)
 ; CHECK-RV32-NEXT:  .LBB6_5: # %dest_2
 ; CHECK-RV32-NEXT:    #APP
Index: llvm/lib/CodeGen/BranchRelaxation.cpp
===================================================================
--- llvm/lib/CodeGen/BranchRelaxation.cpp
+++ llvm/lib/CodeGen/BranchRelaxation.cpp
@@ -18,6 +18,7 @@
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/Config/llvm-config.h"
+#include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
@@ -87,7 +88,9 @@
   bool relaxBranchInstructions();
   void scanFunction();
 
-  MachineBasicBlock *createNewBlockAfter(MachineBasicBlock &BB);
+  MachineBasicBlock *createNewBlockAfter(MachineBasicBlock &OrigMBB);
+  MachineBasicBlock *createNewBlockAfter(MachineBasicBlock &OrigMBB,
+                                         const BasicBlock *BB);
 
   MachineBasicBlock *splitBlockBeforeInstr(MachineInstr &MI,
                                            MachineBasicBlock *DestBB);
@@ -201,12 +204,20 @@
   }
 }
 
-/// Insert a new empty basic block and insert it after \BB
-MachineBasicBlock *BranchRelaxation::createNewBlockAfter(MachineBasicBlock &BB) {
+/// Insert a new empty MachineBasicBlock and insert it after \p OrigMBB
+MachineBasicBlock *
+BranchRelaxation::createNewBlockAfter(MachineBasicBlock &OrigBB) {
+  return createNewBlockAfter(OrigBB, OrigBB.getBasicBlock());
+}
+
+/// Insert a new empty MachineBasicBlock with \p BB as its BasicBlock
+/// and insert it after \p OrigMBB
+MachineBasicBlock *
+BranchRelaxation::createNewBlockAfter(MachineBasicBlock &OrigMBB,
+                                      const BasicBlock *BB) {
   // Create a new MBB for the code after the OrigBB.
-  MachineBasicBlock *NewBB =
-      MF->CreateMachineBasicBlock(BB.getBasicBlock());
-  MF->insert(++BB.getIterator(), NewBB);
+  MachineBasicBlock *NewBB = MF->CreateMachineBasicBlock(BB);
+  MF->insert(++OrigMBB.getIterator(), NewBB);
 
   // Insert an entry into BlockInfo to align it properly with the block numbers.
   BlockInfo.insert(BlockInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
@@ -466,7 +477,8 @@
   // Create the optional restore block and, initially, place it at the end of
   // function. That block will be placed later if it's used; otherwise, it will
   // be erased.
-  MachineBasicBlock *RestoreBB = createNewBlockAfter(MF->back());
+  MachineBasicBlock *RestoreBB = createNewBlockAfter(MF->back(),
+                                                     DestBB->getBasicBlock());
 
   TII->insertIndirectBranch(*BranchBB, *DestBB, *RestoreBB, DL,
                             DestOffset - SrcOffset, RS.get());


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