Revert "cmd/compile: ensure spills of int/float reg args land in abi slots"

This reverts CL 308510.

Reason for revert: It breaks "GOEXPERIMENT=regabi,regabiargs ./make.bash"

Change-Id: I553654690ec73120f8a6258dd80623853c430df0
Reviewed-on: https://go-review.googlesource.com/c/go/+/308932
Trust: David Chase <drchase@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/compile/internal/ssa/stackalloc.go

@@ -218,15 +218,8 @@ func (s *stackAllocState) stackalloc() {
 			// If this is a named value, try to use the name as
 			// the spill location.
 			var name LocalSlot
-			interfere := false
 			if v.Op == OpStoreReg {
-				a := v.Args[0]
-				name = names[a.ID]
-				if name.N == nil && (a.Op == OpArgIntReg || a.Op == OpArgFloatReg) {
-					// Try harder to spill to the abi-provided spill slot, even if the names are messed up.
-					nameOff := a.Aux.(*AuxNameOffset)
-					name = LocalSlot{N: nameOff.Name, Type: v.Type, Off: nameOff.Offset}
-				}
+				name = names[v.Args[0].ID]
 			} else {
 				name = names[v.ID]
 			}
@@ -237,7 +230,6 @@ func (s *stackAllocState) stackalloc() {
 						// A variable can interfere with itself.
 						// It is rare, but it can happen.
 						s.nSelfInterfere++
-						interfere = true
 						goto noname
 					}
 				}
@@ -279,11 +271,7 @@ func (s *stackAllocState) stackalloc() {
 			// Use the stack variable at that index for v.
 			loc := locs[i]
 			if f.pass.debug > stackDebug {
-				reason := "noname"
-				if interfere {
-					reason = "interfere"
-				}
-				fmt.Printf("stackalloc (%s) %s to %s\n", reason, v, loc)
+				fmt.Printf("stackalloc %s to %s\n", v, loc)
 			}
 			f.setHome(v, loc)
 			slots[v.ID] = i