cmd/compile: always include underlying type for map types

This is a different fix for #37716.

Should help make the fix for #46283 easier, since we will no longer
need to keep compiler-generated hash functions and the runtime
hash function in sync.

Change-Id: I84cb93144e425dcd03afc552b5fbd0f2d2cc6d39
Reviewed-on: https://go-review.googlesource.com/c/go/+/322150
Trust: Keith Randall <[email protected]>
Run-TryBot: Keith Randall <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>

Author: randall77

src/cmd/compile/internal/reflectdata/reflect.go

@@ -1112,6 +1112,15 @@ func writeType(t *types.Type) *obj.LSym {
 		}
 		ot = objw.Uint32(lsym, ot, flags)
 		ot = dextratype(lsym, ot, t, 0)
+		if u := t.Underlying(); u != t {
+			// If t is a named map type, also keep the underlying map
+			// type live in the binary. This is important to make sure that
+			// a named map and that same map cast to its underlying type via
+			// reflection, use the same hash function. See issue 37716.
+			r := obj.Addrel(lsym)
+			r.Sym = writeType(u)
+			r.Type = objabi.R_KEEP
+		}
 
 	case types.TPTR:
 		if t.Elem().Kind() == types.TANY {

src/cmd/internal/objabi/reloctype.go

@@ -101,6 +101,9 @@ const (
 	// *rtype, and may be set to zero by the linker if it determines the method
 	// text is unreachable by the linked program.
 	R_METHODOFF
+	// R_KEEP tells the linker to keep the referred-to symbol in the final binary
+	// if the symbol containing the R_KEEP relocation is in the final binary.
+	R_KEEP
 	R_POWER_TOC
 	R_GOTPCREL
 	// R_JMPMIPS (only used on mips64) resolves to non-PC-relative target address

src/cmd/internal/objabi/reloctype_string.go

@@ -178,28 +178,11 @@ func typehash(t *_type, p unsafe.Pointer, h uintptr) uintptr {
 		return h
 	case kindStruct:
 		s := (*structtype)(unsafe.Pointer(t))
-		memStart := uintptr(0)
-		memEnd := uintptr(0)
 		for _, f := range s.fields {
-			if memEnd > memStart && (f.name.isBlank() || f.offset() != memEnd || f.typ.tflag&tflagRegularMemory == 0) {
-				// flush any pending regular memory hashing
-				h = memhash(add(p, memStart), h, memEnd-memStart)
-				memStart = memEnd
-			}
 			if f.name.isBlank() {
 				continue
 			}
-			if f.typ.tflag&tflagRegularMemory == 0 {
-				h = typehash(f.typ, add(p, f.offset()), h)
-				continue
-			}
-			if memStart == memEnd {
-				memStart = f.offset()
-			}
-			memEnd = f.offset() + f.typ.size
-		}
-		if memEnd > memStart {
-			h = memhash(add(p, memStart), h, memEnd-memStart)
+			h = typehash(f.typ, add(p, f.offset()), h)
 		}
 		return h
 	default:

src/runtime/alg.go

@@ -1148,31 +1148,6 @@ func SemNwait(addr *uint32) uint32 {
 	return atomic.Load(&root.nwait)
 }
 
-// MapHashCheck computes the hash of the key k for the map m, twice.
-// Method 1 uses the built-in hasher for the map.
-// Method 2 uses the typehash function (the one used by reflect).
-// Returns the two hash values, which should always be equal.
-func MapHashCheck(m interface{}, k interface{}) (uintptr, uintptr) {
-	// Unpack m.
-	mt := (*maptype)(unsafe.Pointer(efaceOf(&m)._type))
-	mh := (*hmap)(efaceOf(&m).data)
-
-	// Unpack k.
-	kt := efaceOf(&k)._type
-	var p unsafe.Pointer
-	if isDirectIface(kt) {
-		q := efaceOf(&k).data
-		p = unsafe.Pointer(&q)
-	} else {
-		p = efaceOf(&k).data
-	}
-
-	// Compute the hash functions.
-	x := mt.hasher(noescape(p), uintptr(mh.hash0))
-	y := typehash(kt, noescape(p), uintptr(mh.hash0))
-	return x, y
-}
-
 // mspan wrapper for testing.
 //go:notinheap
 type MSpan mspan

src/runtime/export_test.go

@@ -8,7 +8,6 @@ import (
 	"fmt"
 	"math"
 	"math/rand"
-	"reflect"
 	. "runtime"
 	"strings"
 	"testing"
@@ -49,54 +48,6 @@ func TestMemHash64Equality(t *testing.T) {
 	}
 }
 
-func TestCompilerVsRuntimeHash(t *testing.T) {
-	// Test to make sure the compiler's hash function and the runtime's hash function agree.
-	// See issue 37716.
-	for _, m := range []interface{}{
-		map[bool]int{},
-		map[int8]int{},
-		map[uint8]int{},
-		map[int16]int{},
-		map[uint16]int{},
-		map[int32]int{},
-		map[uint32]int{},
-		map[int64]int{},
-		map[uint64]int{},
-		map[int]int{},
-		map[uint]int{},
-		map[uintptr]int{},
-		map[*byte]int{},
-		map[chan int]int{},
-		map[unsafe.Pointer]int{},
-		map[float32]int{},
-		map[float64]int{},
-		map[complex64]int{},
-		map[complex128]int{},
-		map[string]int{},
-		//map[interface{}]int{},
-		//map[interface{F()}]int{},
-		map[[8]uint64]int{},
-		map[[8]string]int{},
-		map[struct{ a, b, c, d int32 }]int{}, // Note: tests AMEM128
-		map[struct{ a, b, _, d int32 }]int{},
-		map[struct {
-			a, b int32
-			c    float32
-			d, e [8]byte
-		}]int{},
-		map[struct {
-			a int16
-			b int64
-		}]int{},
-	} {
-		k := reflect.New(reflect.TypeOf(m).Key()).Elem().Interface() // the zero key
-		x, y := MapHashCheck(m, k)
-		if x != y {
-			t.Errorf("hashes did not match (%x vs %x) for map %T", x, y, m)
-		}
-	}
-}
-
 // Smhasher is a torture test for hash functions.
 // https://code.google.com/p/smhasher/
 // This code is a port of some of the Smhasher tests to Go.