Change ARM VFP VLDM/VSTM instructions to use addressing mode #4, just like

all the other LDM/STM instructions.  This fixes asm printer crashes when
compiling with -O0.  I've changed one of the NEON tests (vst3.ll) to run
with -O0 to check this in the future.

Prior to this change VLDM/VSTM used addressing mode #5, but not really.
The offset field was used to hold a count of the number of registers being
loaded or stored, and the AM5 opcode field was expanded to specify the IA
or DB mode, instead of the standard ADD/SUB specifier.  Much of the backend
was not aware of these special cases.  The crashes occured when rewriting
a frameindex caused the AM5 offset field to be changed so that it did not
have a valid submode.  I don't know exactly what changed to expose this now.
Maybe we've never done much with -O0 and NEON.  Regardless, there's no longer
any reason to keep a count of the VLDM/VSTM registers, so we can use
addressing mode #4 and clean things up in a lot of places.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112322 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARMCodeEmitter.cpp

@@ -1549,7 +1549,7 @@ ARMCodeEmitter::emitVFPLoadStoreMultipleInstruction(const MachineInstr &MI) {
 
   // Set addressing mode by modifying bits U(23) and P(24)
   const MachineOperand &MO = MI.getOperand(OpIdx++);
-  Binary |= getAddrModeUPBits(ARM_AM::getAM5SubMode(MO.getImm()));
+  Binary |= getAddrModeUPBits(ARM_AM::getAM4SubMode(MO.getImm()));
 
   // Set bit W(21)
   if (IsUpdating)
@@ -1558,7 +1558,7 @@ ARMCodeEmitter::emitVFPLoadStoreMultipleInstruction(const MachineInstr &MI) {
   // First register is encoded in Dd.
   Binary |= encodeVFPRd(MI, OpIdx+2);
 
-  // Number of registers are encoded in offset field.
+  // Count the number of registers.
   unsigned NumRegs = 1;
   for (unsigned i = OpIdx+3, e = MI.getNumOperands(); i != e; ++i) {
     const MachineOperand &MO = MI.getOperand(i);