[CodeGen] Store SP adjustment in MachineBasicBlock. NFCI.

Record the SP adjustment on entry to each basic block. This is almost
always zero except on targets like ARM which can split a basic block in
the middle of a call sequence.

This simplifies PEI::replaceFrameIndices which previously had to visit
basic blocks in a specific order and had special handling for
unreachable blocks. More importantly it paves the way for an equally
simple implementation of a backwards version of replaceFrameIndices,
which is required to fully convert PrologEpilogInserter to backwards
register scavenging, which is preferred because it does not rely on
accurate kill flags.

Differential Revision: https://reviews.llvm.org/D154281

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 231544494c32..0ccca7e1bea8 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -570,6 +570,11 @@ void MachineBasicBlock::printName(raw_ostream &os, unsigned printNameFlags,
       os << "bb_id " << *getBBID();
       hasAttributes = true;
     }
+    if (SPAdjustment != 0) {
+      os << (hasAttributes ? ", " : " (");
+      os << "sp-adjustment " << SPAdjustment;
+      hasAttributes = true;
+    }
   }
 
   if (hasAttributes)