cmd/compile,runtime: provide index information on bounds check failure

A few examples (for accessing a slice of length 3):

   s[-1]    runtime error: index out of range [-1]
   s[3]     runtime error: index out of range [3] with length 3
   s[-1:0]  runtime error: slice bounds out of range [-1:]
   s[3:0]   runtime error: slice bounds out of range [3:0]
   s[3:-1]  runtime error: slice bounds out of range [:-1]
   s[3:4]   runtime error: slice bounds out of range [:4] with capacity 3
   s[0:3:4] runtime error: slice bounds out of range [::4] with capacity 3

Note that in cases where there are multiple things wrong with the
indexes (e.g. s[3:-1]), we report one of those errors kind of
arbitrarily, currently the rightmost one.

An exhaustive set of examples is in issue30116[u].out in the CL.

The message text has the same prefix as the old message text. That
leads to slightly awkward phrasing but hopefully minimizes the chance
that code depending on the error text will break.

Increases the size of the go binary by 0.5% (amd64). The panic functions
take arguments in registers in order to keep the size of the compiled code
as small as possible.

Fixes #30116

Change-Id: Idb99a827b7888822ca34c240eca87b7e44a04fdd
Reviewed-on: https://go-review.googlesource.com/c/go/+/161477
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

1 files changed, 105 insertions, 0 deletions

diff --git a/src/runtime/panic32.go b/src/runtime/panic32.go
new file mode 100644
index 0000000000..b89ce9d563
--- /dev/null
+++ b/src/runtime/panic32.go
@@ -0,0 +1,105 @@
+// Copyright 2019 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.
+
+// +build 386 amd64p32 arm mips mipsle
+
+package runtime
+
+// Additional index/slice error paths for 32-bit platforms.
+// Used when the high word of a 64-bit index is not zero.
+
+// failures in the comparisons for s[x], 0 <= x < y (y == len(s))
+func goPanicExtendIndex(hi int, lo uint, y int) {
+	panicCheck1(getcallerpc(), "index out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: true, y: y, code: boundsIndex})
+}
+func goPanicExtendIndexU(hi uint, lo uint, y int) {
+	panicCheck1(getcallerpc(), "index out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: false, y: y, code: boundsIndex})
+}
+
+// failures in the comparisons for s[:x], 0 <= x <= y (y == len(s) or cap(s))
+func goPanicExtendSliceAlen(hi int, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: true, y: y, code: boundsSliceAlen})
+}
+func goPanicExtendSliceAlenU(hi uint, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: false, y: y, code: boundsSliceAlen})
+}
+func goPanicExtendSliceAcap(hi int, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: true, y: y, code: boundsSliceAcap})
+}
+func goPanicExtendSliceAcapU(hi uint, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: false, y: y, code: boundsSliceAcap})
+}
+
+// failures in the comparisons for s[x:y], 0 <= x <= y
+func goPanicExtendSliceB(hi int, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: true, y: y, code: boundsSliceB})
+}
+func goPanicExtendSliceBU(hi uint, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: false, y: y, code: boundsSliceB})
+}
+
+// failures in the comparisons for s[::x], 0 <= x <= y (y == len(s) or cap(s))
+func goPanicExtendSlice3Alen(hi int, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: true, y: y, code: boundsSlice3Alen})
+}
+func goPanicExtendSlice3AlenU(hi uint, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: false, y: y, code: boundsSlice3Alen})
+}
+func goPanicExtendSlice3Acap(hi int, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: true, y: y, code: boundsSlice3Acap})
+}
+func goPanicExtendSlice3AcapU(hi uint, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: false, y: y, code: boundsSlice3Acap})
+}
+
+// failures in the comparisons for s[:x:y], 0 <= x <= y
+func goPanicExtendSlice3B(hi int, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: true, y: y, code: boundsSlice3B})
+}
+func goPanicExtendSlice3BU(hi uint, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: false, y: y, code: boundsSlice3B})
+}
+
+// failures in the comparisons for s[x:y:], 0 <= x <= y
+func goPanicExtendSlice3C(hi int, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: true, y: y, code: boundsSlice3C})
+}
+func goPanicExtendSlice3CU(hi uint, lo uint, y int) {
+	panicCheck1(getcallerpc(), "slice bounds out of range")
+	panic(boundsError{x: int64(hi)<<32 + int64(lo), signed: false, y: y, code: boundsSlice3C})
+}
+
+// Implemented in assembly, as they take arguments in registers.
+// Declared here to mark them as ABIInternal.
+func panicExtendIndex(hi int, lo uint, y int)
+func panicExtendIndexU(hi uint, lo uint, y int)
+func panicExtendSliceAlen(hi int, lo uint, y int)
+func panicExtendSliceAlenU(hi uint, lo uint, y int)
+func panicExtendSliceAcap(hi int, lo uint, y int)
+func panicExtendSliceAcapU(hi uint, lo uint, y int)
+func panicExtendSliceB(hi int, lo uint, y int)
+func panicExtendSliceBU(hi uint, lo uint, y int)
+func panicExtendSlice3Alen(hi int, lo uint, y int)
+func panicExtendSlice3AlenU(hi uint, lo uint, y int)
+func panicExtendSlice3Acap(hi int, lo uint, y int)
+func panicExtendSlice3AcapU(hi uint, lo uint, y int)
+func panicExtendSlice3B(hi int, lo uint, y int)
+func panicExtendSlice3BU(hi uint, lo uint, y int)
+func panicExtendSlice3C(hi int, lo uint, y int)
+func panicExtendSlice3CU(hi uint, lo uint, y int)