R600/SI: Report offset in correct units for st64 DS instructions

[arsenm]

Summary

Need to convert the 64 element offset into bytes, not just the element
size like the normal case instructions.

Noticed by inspection. This can't be hit now because
st64 instructions aren't emitted during instruction selection,
and the post-RA scheduler isn't enabled.

[arsenm]

r217560

lib/Target/R600/SIInstrInfo.cpp

   return false;
 }
 
+static bool isStride64(unsigned Opc) {
+  switch (Opc) {
+  case AMDGPU::DS_READ2ST64_B32:
+  case AMDGPU::DS_READ2ST64_B64:
+  case AMDGPU::DS_WRITE2ST64_B32:
+  case AMDGPU::DS_WRITE2ST64_B64:
+    return true;
+  default:
+    return false;
+  }
+}
+
 bool SIInstrInfo::getLdStBaseRegImmOfs(MachineInstr *LdSt,
                                        unsigned &BaseReg, unsigned &Offset,
                                        const TargetRegisterInfo *TRI) const {

         EltSize = getOpRegClass(*LdSt, Data0Idx)->getSize();
       }
 
+      if (isStride64(Opc))
+        EltSize *= 64;
+
       const MachineOperand *AddrReg = getNamedOperand(*LdSt,
                                                       AMDGPU::OpName::addr);
       BaseReg = AddrReg->getReg();