Mark all PPC CR registers to be spilled as live-in and tag MFCR appropriately

Leaving MFCR has having unmodeled side effects is not enough to prevent
unwanted instruction reordering post-RA. We could probably apply a stronger
barrier attribute, but there is a better way: Add all (not just the first) CR
to be spilled as live-in to the entry block, and add all CRs to the MFCR
instruction as implicitly killed.

Unfortunately, I don't have a small test case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179465 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/PPCInstr64Bit.td

@@ -256,11 +256,7 @@ def MFCR8pseud: XFXForm_3<31, 19, (outs G8RC:$rT), (ins crbitm:$FXM),
             PPC970_MicroCode, PPC970_Unit_CRU;
 } // neverHasSideEffects = 1
 
-// MFCR uses all CR registers, but marking that explicitly causes
-// problems because some of them appear to be undefined. Because
-// this form is used only in prologue code, just mark it as having
-// side effects.
-let /* Uses = [CR0, CR1, CR2, CR3, CR4, CR5, CR6] */ hasSideEffects = 1 in
+let neverHasSideEffects = 1 in
 def MFCR8 : XFXForm_3<31, 19, (outs G8RC:$rT), (ins),
                      "mfcr $rT", SprMFCR>,
                      PPC970_MicroCode, PPC970_Unit_CRU;