6g, 8g: handle slice by sub-word-sized index (uint8, int8, uint16, int16)

R=ken2
CC=golang-dev
https://golang.org/cl/1960042

4 files changed, 73 insertions, 16 deletions

diff --git a/src/cmd/6g/ggen.c b/src/cmd/6g/ggen.c
index 46ca326745..1e045da8ba 100644
--- a/src/cmd/6g/ggen.c
+++ b/src/cmd/6g/ggen.c
@@ -1145,16 +1145,18 @@ cmpandthrow(Node *nl, Node *nr)
 
 	n1.op = OXXX;
 	t = types[TUINT32];
-	if(is64(nl->type) || is64(nr->type)) {
-		// two 64-bit is just a 64-bit compare,
-		// but one 32 and one 64 needs to copy
-		// the 32 into a register to get the full comparison.
-		t = types[TUINT64];
-		if(!is64(nl->type) && nl->op != OLITERAL) {
+	if(nl->type->width != t->width || nr->type->width != t->width) {
+		if((is64(nl->type) && nl->op != OLITERAL) || (is64(nr->type) && nr->op != OLITERAL))
+			t = types[TUINT64];
+
+		// Check if we need to use a temporary.
+		// At least one of the arguments is 32 bits
+		// (the len or cap) so one temporary suffices.
+		if(nl->type->width != t->width && nl->op != OLITERAL) {
 			regalloc(&n1, t, nl);
 			gmove(nl, &n1);
 			nl = &n1;
-		} else if(!is64(nr->type) && nr->op != OLITERAL) {
+		} else if(nr->type->width != t->width && nr->op != OLITERAL) {
 			regalloc(&n1, t, nr);
 			gmove(nr, &n1);
 			nr = &n1;
diff --git a/src/cmd/8g/ggen.c b/src/cmd/8g/ggen.c
index 40f348c7d8..5c51833ea2 100644
--- a/src/cmd/8g/ggen.c
+++ b/src/cmd/8g/ggen.c
@@ -857,7 +857,8 @@ cmpandthrow(Node *nl, Node *nr)
 	vlong cl;
 	Prog *p1;
 	int op;
-	Node *c;
+	Node *c, n1;
+	Type *t;
 
 	op = OLE;
 	if(smallintconst(nl)) {
@@ -872,16 +873,34 @@ cmpandthrow(Node *nl, Node *nr)
 		nl = nr;
 		nr = c;
 	}
-
-	gins(optoas(OCMP, types[TUINT32]), nl, nr);
+	
+	// Arguments are known not to be 64-bit,
+	// but they might be smaller than 32 bits.
+	// Check if we need to use a temporary.
+	// At least one of the arguments is 32 bits
+	// (the len or cap) so one temporary suffices.
+	n1.op = OXXX;
+	t = types[TUINT32];
+	if(nl->type->width != t->width) {
+		regalloc(&n1, t, nl);
+		gmove(nl, &n1);
+		nl = &n1;
+	} else if(nr->type->width != t->width) {
+		regalloc(&n1, t, nr);
+		gmove(nr, &n1);
+		nr = &n1;
+	}
+	gins(optoas(OCMP, t), nl, nr);
+	if(n1.op != OXXX)
+		regfree(&n1);
 	if(throwpc == nil) {
-		p1 = gbranch(optoas(op, types[TUINT32]), T);
+		p1 = gbranch(optoas(op, t), T);
 		throwpc = pc;
 		ginscall(panicslice, 0);
 		patch(p1, pc);
 	} else {
 		op = brcom(op);
-		p1 = gbranch(optoas(op, types[TUINT32]), T);
+		p1 = gbranch(optoas(op, t), T);
 		patch(p1, throwpc);
 	}
 }
@@ -1045,6 +1064,7 @@ sliceslice:
 		// if(lb[1] > old.nel[0]) goto throw;
 		n2 = nodes[0];
 		n2.xoffset += Array_nel;
+		n2.type = types[TUINT32];
 		cmpandthrow(&nodes[1], &n2);
 
 		// ret.nel = old.nel[0]-lb[1];
@@ -1064,6 +1084,7 @@ sliceslice:
 		// if(hb[2] > old.cap[0]) goto throw;
 		n2 = nodes[0];
 		n2.xoffset += Array_cap;
+		n2.type = types[TUINT32];
 		cmpandthrow(&nodes[2], &n2);
 
 		// if(lb[1] > hb[2]) goto throw;
diff --git a/src/pkg/exp/draw/x11/auth.go b/src/pkg/exp/draw/x11/auth.go
index b4c75a360d..896dedf05c 100644
--- a/src/pkg/exp/draw/x11/auth.go
+++ b/src/pkg/exp/draw/x11/auth.go
@@ -16,10 +16,7 @@ func readU16BE(r io.Reader, b []byte) (uint16, os.Error) {
 	if err != nil {
 		return 0, err
 	}
-	// TODO(nigeltao): remove the workaround when bug 1011 gets fixed.
-	//return uint16(b[0])<<8 + uint16(b[1]), nil
-	ret := uint16(b[0])<<8 + uint16(b[1])
-	return ret, nil
+	return uint16(b[0])<<8 + uint16(b[1]), nil
 }
 
 // readStr reads a length-prefixed string from r, using b as a scratch buffer.
diff --git a/test/fixedbugs/bug303.go b/test/fixedbugs/bug303.go
new file mode 100644
index 0000000000..3bd790f136
--- /dev/null
+++ b/test/fixedbugs/bug303.go
@@ -0,0 +1,37 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 1011.  Removing either #1 or #3 avoided the crash at #2.
+
+package main
+
+import (
+	"io"
+	"strings"
+)
+
+func readU16BE(b []byte) uint16 {
+	b[0] = 0
+	b[1] = 1
+	return uint16(b[0])<<8 + uint16(b[1]) // #1
+	n := uint16(b[0])<<8 + uint16(b[1])
+	return n
+}
+
+func readStr(r io.Reader, b []byte) string {
+	n := readU16BE(b)
+	if int(n) > len(b) {
+		return "err: n>b"
+	}
+	io.ReadFull(r, b[0:n]) // #2
+	return string(b[0:n])  // #3
+	return "ok"
+}
+
+func main() {
+	br := strings.NewReader("abcd")
+	readStr(br, make([]byte, 256))
+}