[dev.ssa] cmd/compile: make sure we don't move loads between blocks

This can lead to multiple stores being live at once.

Do OINDEX and ODOT using addresses & loads instead of specific ops.
This keeps SSA values from containing unSSAable types.

Change-Id: I79567e9d43cdee09084eb89ea0bd7aa3aad48ada
Reviewed-on: https://go-review.googlesource.com/15654
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>

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

@@ -1732,8 +1732,9 @@ func (s *state) expr(n *Node) *ssa.Value {
 		return s.newValue2(ssa.OpLoad, n.Type, p, s.mem())
 
 	case ODOT:
-		v := s.expr(n.Left)
+		// TODO: fix when we can SSA struct types.
-		return s.newValue1I(ssa.OpStructSelect, n.Type, n.Xoffset, v)
+		p := s.addr(n)
+		return s.newValue2(ssa.OpLoad, n.Type, p, s.mem())
 
 	case ODOTPTR:
 		p := s.expr(n.Left)
@@ -1742,29 +1743,29 @@ func (s *state) expr(n *Node) *ssa.Value {
 		return s.newValue2(ssa.OpLoad, n.Type, p, s.mem())
 
 	case OINDEX:
-		if n.Left.Type.Bound >= 0 { // array or string
+		switch {
+		case n.Left.Type.IsString():
 			a := s.expr(n.Left)
 			i := s.expr(n.Right)
 			i = s.extendIndex(i)
-			if n.Left.Type.IsString() {
+			if !n.Bounded {
-				if !n.Bounded {
+				len := s.newValue1(ssa.OpStringLen, Types[TINT], a)
-					len := s.newValue1(ssa.OpStringLen, Types[TINT], a)
+				s.boundsCheck(i, len)
-					s.boundsCheck(i, len)
-				}
-				ptrtyp := Ptrto(Types[TUINT8])
-				ptr := s.newValue1(ssa.OpStringPtr, ptrtyp, a)
-				ptr = s.newValue2(ssa.OpAddPtr, ptrtyp, ptr, i)
-				return s.newValue2(ssa.OpLoad, Types[TUINT8], ptr, s.mem())
-			} else {
-				if !n.Bounded {
-					len := s.constInt(Types[TINT], n.Left.Type.Bound)
-					s.boundsCheck(i, len)
-				}
-				return s.newValue2(ssa.OpArrayIndex, n.Left.Type.Type, a, i)
 			}
-		} else { // slice
+			ptrtyp := Ptrto(Types[TUINT8])
+			ptr := s.newValue1(ssa.OpStringPtr, ptrtyp, a)
+			ptr = s.newValue2(ssa.OpAddPtr, ptrtyp, ptr, i)
+			return s.newValue2(ssa.OpLoad, Types[TUINT8], ptr, s.mem())
+		case n.Left.Type.IsSlice():
 			p := s.addr(n)
 			return s.newValue2(ssa.OpLoad, n.Left.Type.Type, p, s.mem())
+		case n.Left.Type.IsArray():
+			// TODO: fix when we can SSA arrays of length 1.
+			p := s.addr(n)
+			return s.newValue2(ssa.OpLoad, n.Left.Type.Type, p, s.mem())
+		default:
+			s.Fatalf("bad type for index %v", n.Left.Type)
+			return nil
 		}
 
 	case OLEN, OCAP:

src/cmd/compile/internal/ssa/gen/generic.rules

@@ -75,9 +75,9 @@
 
 // indexing operations
 // Note: bounds check has already been done
-(ArrayIndex (Load ptr mem) idx) -> (Load (PtrIndex <v.Type.PtrTo()> ptr idx) mem)
+(ArrayIndex (Load ptr mem) idx) && b == v.Args[0].Block -> (Load (PtrIndex <v.Type.PtrTo()> ptr idx) mem)
 (PtrIndex <t> ptr idx) -> (AddPtr ptr (MulPtr idx (ConstPtr [t.Elem().Size()])))
-(StructSelect [idx] (Load ptr mem)) -> (Load (OffPtr <v.Type.PtrTo()> [idx] ptr) mem)
+(StructSelect [idx] (Load ptr mem)) && b == v.Args[0].Block -> (Load (OffPtr <v.Type.PtrTo()> [idx] ptr) mem)
 
 // complex ops
 (ComplexReal (ComplexMake real _  )) -> real

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

@@ -136,15 +136,18 @@ func rewriteValuegeneric(v *Value, config *Config) bool {
 		;
 	case OpArrayIndex:
 		// match: (ArrayIndex (Load ptr mem) idx)
-		// cond:
+		// cond: b == v.Args[0].Block
 		// result: (Load (PtrIndex <v.Type.PtrTo()> ptr idx) mem)
 		{
 			if v.Args[0].Op != OpLoad {
-				goto end4894dd7b58383fee5f8a92be08437c33
+				goto end68b373270d9d605c420497edefaa71df
 			}
 			ptr := v.Args[0].Args[0]
 			mem := v.Args[0].Args[1]
 			idx := v.Args[1]
+			if !(b == v.Args[0].Block) {
+				goto end68b373270d9d605c420497edefaa71df
+			}
 			v.Op = OpLoad
 			v.AuxInt = 0
 			v.Aux = nil
@@ -157,8 +160,8 @@ func rewriteValuegeneric(v *Value, config *Config) bool {
 			v.AddArg(mem)
 			return true
 		}
-		goto end4894dd7b58383fee5f8a92be08437c33
+		goto end68b373270d9d605c420497edefaa71df
-	end4894dd7b58383fee5f8a92be08437c33:
+	end68b373270d9d605c420497edefaa71df:
 		;
 	case OpCom16:
 		// match: (Com16 (Com16 x))
@@ -1510,15 +1513,18 @@ func rewriteValuegeneric(v *Value, config *Config) bool {
 		;
 	case OpStructSelect:
 		// match: (StructSelect [idx] (Load ptr mem))
-		// cond:
+		// cond: b == v.Args[0].Block
 		// result: (Load (OffPtr <v.Type.PtrTo()> [idx] ptr) mem)
 		{
 			idx := v.AuxInt
 			if v.Args[0].Op != OpLoad {
-				goto end16fdb45e1dd08feb36e3cc3fb5ed8935
+				goto endd1a92da3e00c16a8f5bd3bd30deca298
 			}
 			ptr := v.Args[0].Args[0]
 			mem := v.Args[0].Args[1]
+			if !(b == v.Args[0].Block) {
+				goto endd1a92da3e00c16a8f5bd3bd30deca298
+			}
 			v.Op = OpLoad
 			v.AuxInt = 0
 			v.Aux = nil
@@ -1531,8 +1537,8 @@ func rewriteValuegeneric(v *Value, config *Config) bool {
 			v.AddArg(mem)
 			return true
 		}
-		goto end16fdb45e1dd08feb36e3cc3fb5ed8935
+		goto endd1a92da3e00c16a8f5bd3bd30deca298
-	end16fdb45e1dd08feb36e3cc3fb5ed8935:
+	endd1a92da3e00c16a8f5bd3bd30deca298:
 		;
 	case OpSub16:
 		// match: (Sub16 x x)