-Revert parts of 84326 and 84411. Distinquishing between fixed and non-fixed
stack slots and giving them different PseudoSourceValue's did not fix the
problem of post-alloc scheduling miscompiling llvm itself.
- Apply Dan's conservative workaround by assuming any non fixed stack slots can
alias other memory locations. This means a load from spill slot #1 cannot 
move above a store of spill slot #2. 
- Enable post-alloc scheduling for x86 at optimization leverl Default and above.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84424 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86InstrBuilder.h b/lib/Target/X86/X86InstrBuilder.h
index 8cbdfec..c475b56 100644
--- a/lib/Target/X86/X86InstrBuilder.h
+++ b/lib/Target/X86/X86InstrBuilder.h
@@ -143,11 +143,8 @@
     Flags |= MachineMemOperand::MOLoad;
   if (TID.mayStore())
     Flags |= MachineMemOperand::MOStore;
-  const Value *SV = (MFI.isFixedObjectIndex(FI) ||
-                     MFI.isSpillSlotObjectIndex(FI))
-    ? PseudoSourceValue::getFixedStack(FI) : PseudoSourceValue::getStack();
   MachineMemOperand *MMO =
-    MF.getMachineMemOperand(SV,
+    MF.getMachineMemOperand(PseudoSourceValue::getFixedStack(FI),
                             Flags, Offset,
                             MFI.getObjectSize(FI),
                             MFI.getObjectAlignment(FI));