cmd/compile: sanitize before/after expansion OpSelectN references

In expand_calls, OpSelectN occurs both before and after the rewriting.
Attempting to rewrite a post-expansion OpSelectN is bad.
(The only ones rewritten in place are the ones returning mem;
others are synthesized to replace other selection chains with
register references.)

Updates #40724.
Updates #44816#issuecomment-815258897.

Change-Id: I7b6022cfb47f808d3ce6cc796c067245f36047f3
Reviewed-on: https://go-review.googlesource.com/c/go/+/308309
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

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

@@ -190,6 +190,7 @@ type expandState struct {
 	commonSelectors    map[selKey]*Value // used to de-dupe selectors
 	commonArgs         map[selKey]*Value // used to de-dupe OpArg/OpArgIntReg/OpArgFloatReg
 	memForCall         map[ID]*Value     // For a call, need to know the unique selector that gets the mem.
+	transformedSelects map[ID]bool       // OpSelectN after rewriting, either created or renumbered.
 	indentLevel        int               // Indentation for debugging recursion
 }
 
@@ -393,10 +394,17 @@ func (x *expandState) rewriteSelect(leaf *Value, selector *Value, offset int64,
 		call0 := call
 		aux := call.Aux.(*AuxCall)
 		which := selector.AuxInt
+		if x.transformedSelects[selector.ID] {
+			// This is a minor hack.  Either this select has had its operand adjusted (mem) or
+			// it is some other intermediate node that was rewritten to reference a register (not a generic arg).
+			// This can occur with chains of selection/indexing from single field/element aggregates.
+			leaf.copyOf(selector)
+			break
+		}
 		if which == aux.NResults() { // mem is after the results.
 			// rewrite v as a Copy of call -- the replacement call will produce a mem.
 			if leaf != selector {
-				panic("Unexpected selector of memory")
+				panic(fmt.Errorf("Unexpected selector of memory, selector=%s, call=%s, leaf=%s", selector.LongString(), call.LongString(), leaf.LongString()))
 			}
 			if aux.abiInfo == nil {
 				panic(badVal("aux.abiInfo nil for call", call))
@@ -404,6 +412,7 @@ func (x *expandState) rewriteSelect(leaf *Value, selector *Value, offset int64,
 			if existing := x.memForCall[call.ID]; existing == nil {
 				selector.AuxInt = int64(aux.abiInfo.OutRegistersUsed())
 				x.memForCall[call.ID] = selector
+				x.transformedSelects[selector.ID] = true // operand adjusted
 			} else {
 				selector.copyOf(existing)
 			}
@@ -421,6 +430,7 @@ func (x *expandState) rewriteSelect(leaf *Value, selector *Value, offset int64,
 					call = mem
 				} else {
 					mem = call.Block.NewValue1I(call.Pos.WithNotStmt(), OpSelectN, types.TypeMem, int64(aux.abiInfo.OutRegistersUsed()), call)
+					x.transformedSelects[mem.ID] = true // select uses post-expansion indexing
 					x.memForCall[call.ID] = mem
 					call = mem
 				}
@@ -436,8 +446,10 @@ func (x *expandState) rewriteSelect(leaf *Value, selector *Value, offset int64,
 						leaf.SetArgs1(call0)
 						leaf.Type = leafType
 						leaf.AuxInt = reg
+						x.transformedSelects[leaf.ID] = true // leaf, rewritten to use post-expansion indexing.
 					} else {
 						w := call.Block.NewValue1I(leaf.Pos, OpSelectN, leafType, reg, call0)
+						x.transformedSelects[w.ID] = true // select, using post-expansion indexing.
 						leaf.copyOf(w)
 					}
 				} else {
@@ -1038,6 +1050,7 @@ func expandCalls(f *Func) {
 		sdom:               f.Sdom(),
 		commonArgs:         make(map[selKey]*Value),
 		memForCall:         make(map[ID]*Value),
+		transformedSelects: make(map[ID]bool),
 	}
 
 	// For 32-bit, need to deal with decomposition of 64-bit integers, which depends on endianness.

test/abi/bad_select_crash.dir/genCaller42/genCaller42.go

@@ -0,0 +1,71 @@
+package genCaller42
+
+import "bad_select_crash.dir/genChecker42"
+import "bad_select_crash.dir/genUtils"
+import "reflect"
+
+
+func Caller2() {
+  genUtils.BeginFcn()
+  c0 := genChecker42.StructF2S0{F0: genChecker42.ArrayF2S1E1{genChecker42.New_3(float64(-0.4418990509835844))}}
+  c1 := genChecker42.ArrayF2S2E1{genChecker42.StructF2S1{/* _: "񊶿(z̽|" */F1: "􂊇񊶿"}}
+  c2 := int16(4162)
+  c3 := float32(-7.667096e+37)
+  c4 := int64(3202175648847048679)
+  var p0 genChecker42.ArrayF2S0E0
+  p0 = genChecker42.ArrayF2S0E0{}
+  var p1 uint8
+  p1 = uint8(57)
+  var p2 uint16
+  p2 = uint16(10920)
+  var p3 float64
+  p3 = float64(-1.597256501942112)
+  genUtils.Mode = ""
+  // 5 returns 4 params
+  r0, r1, r2, r3, r4 := genChecker42.Test2(p0, p1, p2, p3)
+  if !genChecker42.EqualStructF2S0(r0, c0) {
+    genUtils.NoteFailure(9, 42, 2, "genChecker42", "return", 0, true, uint64(0))
+  }
+  if r1 != c1 {
+    genUtils.NoteFailure(9, 42, 2, "genChecker42", "return", 1, true, uint64(0))
+  }
+  if r2 != c2 {
+    genUtils.NoteFailure(9, 42, 2, "genChecker42", "return", 2, true, uint64(0))
+  }
+  if r3 != c3 {
+    genUtils.NoteFailure(9, 42, 2, "genChecker42", "return", 3, true, uint64(0))
+  }
+  if r4 != c4 {
+    genUtils.NoteFailure(9, 42, 2, "genChecker42", "return", 4, true, uint64(0))
+  }
+  // same call via reflection
+  genUtils.Mode = "reflect"
+  rc := reflect.ValueOf(genChecker42.Test2)
+  rvslice :=   rc.Call([]reflect.Value{reflect.ValueOf(p0), reflect.ValueOf(p1), reflect.ValueOf(p2), reflect.ValueOf(p3)})
+  rr0i := rvslice[0].Interface()
+  rr0v:= rr0i.( genChecker42.StructF2S0)
+  if !genChecker42.EqualStructF2S0(rr0v, c0) {
+    genUtils.NoteFailure(9, 42, 2, "genChecker42", "return", 0, true, uint64(0))
+  }
+  rr1i := rvslice[1].Interface()
+  rr1v:= rr1i.( genChecker42.ArrayF2S2E1)
+  if rr1v != c1 {
+    genUtils.NoteFailure(9, 42, 2, "genChecker42", "return", 1, true, uint64(0))
+  }
+  rr2i := rvslice[2].Interface()
+  rr2v:= rr2i.( int16)
+  if rr2v != c2 {
+    genUtils.NoteFailure(9, 42, 2, "genChecker42", "return", 2, true, uint64(0))
+  }
+  rr3i := rvslice[3].Interface()
+  rr3v:= rr3i.( float32)
+  if rr3v != c3 {
+    genUtils.NoteFailure(9, 42, 2, "genChecker42", "return", 3, true, uint64(0))
+  }
+  rr4i := rvslice[4].Interface()
+  rr4v:= rr4i.( int64)
+  if rr4v != c4 {
+    genUtils.NoteFailure(9, 42, 2, "genChecker42", "return", 4, true, uint64(0))
+  }
+  genUtils.EndFcn()
+}

test/abi/bad_select_crash.dir/genChecker42/genChecker42.go

@@ -0,0 +1,135 @@
+package genChecker42
+
+import "bad_select_crash.dir/genUtils"
+
+type StructF0S0 struct {
+}
+
+type ArrayF0S0E2 [2]int16
+
+type ArrayF0S1E1 [1]StructF0S0
+
+type StructF1S0 struct {
+F0 StructF1S1
+_ ArrayF1S0E4
+}
+
+type StructF1S1 struct {
+}
+
+type StructF1S2 struct {
+F0 uint32
+F1 uint8
+F2 string
+F3 string
+F4 ArrayF1S1E1
+}
+
+type StructF1S3 struct {
+F0 float64
+}
+
+type StructF1S4 struct {
+_ int32
+F1 float32
+}
+
+type StructF1S5 struct {
+F0 uint16
+}
+
+type StructF1S6 struct {
+F0 uint8
+F1 uint32
+}
+
+type ArrayF1S0E4 [4]float64
+
+type ArrayF1S1E1 [1]StructF1S3
+
+type ArrayF1S2E2 [2]StructF1S4
+
+type ArrayF1S3E2 [2]StructF1S5
+
+type ArrayF1S4E4 [4]ArrayF1S5E3
+
+type ArrayF1S5E3 [3]string
+
+type ArrayF1S6E1 [1]float64
+
+type StructF2S0 struct {
+F0 ArrayF2S1E1
+}
+
+// equal func for StructF2S0
+//go:noinline
+func EqualStructF2S0(left StructF2S0, right StructF2S0) bool {
+  return   EqualArrayF2S1E1(left.F0, right.F0)
+}
+
+type StructF2S1 struct {
+_ string
+F1 string
+}
+
+type ArrayF2S0E0 [0]int8
+
+type ArrayF2S1E1 [1]*float64
+
+// equal func for ArrayF2S1E1
+//go:noinline
+func EqualArrayF2S1E1(left ArrayF2S1E1, right ArrayF2S1E1) bool {
+  return *left[0] == *right[0]
+}
+
+type ArrayF2S2E1 [1]StructF2S1
+
+// 5 returns 4 params
+//go:registerparams
+//go:noinline
+func Test2(p0 ArrayF2S0E0, p1 uint8, _ uint16, p3 float64) (r0 StructF2S0, r1 ArrayF2S2E1, r2 int16, r3 float32, r4 int64) {
+  // consume some stack space, so as to trigger morestack
+  var pad [16]uint64
+  pad[genUtils.FailCount&0x1]++
+  rc0 := StructF2S0{F0: ArrayF2S1E1{New_3(float64(-0.4418990509835844))}}
+  rc1 := ArrayF2S2E1{StructF2S1{/* _: "񊶿(z̽|" */F1: "􂊇񊶿"}}
+  rc2 := int16(4162)
+  rc3 := float32(-7.667096e+37)
+  rc4 := int64(3202175648847048679)
+  p1f0c := uint8(57)
+  if p1 != p1f0c {
+    genUtils.NoteFailureElem(9, 42, 2, "genChecker42", "parm", 1, 0, false, pad[0])
+    return
+  }
+  _ = uint16(10920)
+  p3f0c := float64(-1.597256501942112)
+  if p3 != p3f0c {
+    genUtils.NoteFailureElem(9, 42, 2, "genChecker42", "parm", 3, 0, false, pad[0])
+    return
+  }
+  defer func(p0 ArrayF2S0E0, p1 uint8) {
+  // check parm passed
+  // check parm passed
+  if p1 != p1f0c {
+    genUtils.NoteFailureElem(9, 42, 2, "genChecker42", "parm", 1, 0, false, pad[0])
+    return
+  }
+  // check parm captured
+  if p3 != p3f0c {
+    genUtils.NoteFailureElem(9, 42, 2, "genChecker42", "parm", 3, 0, false, pad[0])
+    return
+  }
+  } (p0, p1)
+
+  return rc0, rc1, rc2, rc3, rc4
+  // 0 addr-taken params, 0 addr-taken returns
+}
+
+
+//go:noinline
+func New_3(i float64)  *float64 {
+  x := new( float64)
+  *x = i
+  return x
+}
+

test/abi/bad_select_crash.dir/genMain.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"bad_select_crash.dir/genCaller42"
+	"bad_select_crash.dir/genUtils"
+	"fmt"
+	"os"
+)
+
+func main() {
+	// Only print if there is a problem
+	genCaller42.Caller2()
+	if genUtils.FailCount != 0 {
+		fmt.Fprintf(os.Stderr, "FAILURES: %d\n", genUtils.FailCount)
+		os.Exit(2)
+	}
+}

test/abi/bad_select_crash.dir/genUtils/genUtils.go

@@ -0,0 +1,61 @@
+package genUtils
+
+
+import "fmt"
+import "os"
+
+var ParamFailCount int
+
+var ReturnFailCount int
+
+var FailCount int
+
+var Mode string
+
+type UtilsType int
+
+//go:noinline
+func NoteFailure(cm int, pidx int, fidx int, pkg string, pref string, parmNo int, isret bool,_ uint64) {
+  if isret {
+    if ParamFailCount != 0 {
+      return
+    }
+    ReturnFailCount++
+  } else {
+    ParamFailCount++
+  }
+  fmt.Fprintf(os.Stderr, "Error: fail %s |%d|%d|%d| =%s.Test%d= %s %d\n", Mode, cm, pidx, fidx, pkg, fidx, pref, parmNo)
+
+  if (ParamFailCount + FailCount + ReturnFailCount > 9999) {
+    os.Exit(1)
+  }
+}
+
+//go:noinline
+func NoteFailureElem(cm int, pidx int, fidx int, pkg string, pref string, parmNo int, elem int, isret bool, _ uint64) {
+
+  if isret {
+    if ParamFailCount != 0 {
+      return
+    }
+    ReturnFailCount++
+  } else {
+    ParamFailCount++
+  }
+  fmt.Fprintf(os.Stderr, "Error: fail %s |%d|%d|%d| =%s.Test%d= %s %d elem %d\n", Mode, cm, pidx, fidx, pkg, fidx, pref, parmNo, elem)
+
+  if (ParamFailCount + FailCount + ReturnFailCount > 9999) {
+    os.Exit(1)
+  }
+}
+
+func BeginFcn() {
+  ParamFailCount = 0
+  ReturnFailCount = 0
+}
+
+func EndFcn() {
+  FailCount += ParamFailCount
+  FailCount += ReturnFailCount
+}
+

test/abi/bad_select_crash.dir/go.mod

@@ -0,0 +1,2 @@
+module bad_select_crash.dir
+go 1.14

test/abi/bad_select_crash.go

@@ -0,0 +1,2 @@
+// runindir -goexperiment regabi,regabiargs
+