[CodeGen] Store call frame size in MachineBasicBlock

Record the call frame size on entry to each basic block. This is usually
zero except when a basic block has been split 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/D156113

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 23154449..8e7b2d7 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 (CallFrameSize != 0) {
+      os << (hasAttributes ? ", " : " (");
+      os << "call-frame-size " << CallFrameSize;
+      hasAttributes = true;
+    }
   }
 
   if (hasAttributes)
@@ -1099,6 +1104,7 @@ MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(
   DebugLoc DL;  // FIXME: this is nowhere
 
   MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
+  NMBB->setCallFrameSize(Succ->getCallFrameSize());
 
   // Is there an indirect jump with jump table?
   bool ChangedIndirectJump = false;