Remove MachineRegisterInfo::getLastVirtReg(), it was giving wrong results

when no virtual registers have been allocated.

It was only used to resize IndexedMaps, so provide an IndexedMap::resize()
method such that

 Map.grow(MRI.getLastVirtReg());

can be replaced with the simpler

 Map.resize(MRI.getNumVirtRegs());

This works correctly when no virtuals are allocated, and it bypasses the to/from
index conversions.

llvm-svn: 123130

1 files changed, 1 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/RegAllocFast.cpp b/llvm/lib/CodeGen/RegAllocFast.cpp
index 109da42e9c3..6666d9aaf40 100644
--- a/llvm/lib/CodeGen/RegAllocFast.cpp
+++ b/llvm/lib/CodeGen/RegAllocFast.cpp
@@ -1024,8 +1024,7 @@ bool RAFast::runOnMachineFunction(MachineFunction &Fn) {
 
   // initialize the virtual->physical register map to have a 'null'
   // mapping for all virtual registers
-  unsigned LastVirtReg = MRI->getLastVirtReg();
-  StackSlotForVirtReg.grow(LastVirtReg);
+  StackSlotForVirtReg.resize(MRI->getNumVirtRegs());
 
   // Loop over all of the basic blocks, eliminating virtual register references
   for (MachineFunction::iterator MBBi = Fn.begin(), MBBe = Fn.end();