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, 70 insertions, 0 deletions

diff --git a/src/runtime/asm_amd64.s b/src/runtime/asm_amd64.s
index 85133bf2df..d3e5c54378 100644
--- a/src/runtime/asm_amd64.s
+++ b/src/runtime/asm_amd64.s
@@ -1628,3 +1628,73 @@ TEXT runtime·debugCallPanicked(SB),NOSPLIT,$16-16
 	MOVQ	$2, AX
 	BYTE	$0xcc
 	RET
+
+// Note: these functions use a special calling convention to save generated code space.
+// Arguments are passed in registers, but the space for those arguments are allocated
+// in the caller's stack frame. These stubs write the args into that stack space and
+// then tail call to the corresponding runtime handler.
+// The tail call makes these stubs disappear in backtraces.
+TEXT runtime·panicIndex(SB),NOSPLIT,$0-16
+	MOVQ	AX, x+0(FP)
+	MOVQ	CX, y+8(FP)
+	JMP	runtime·goPanicIndex(SB)
+TEXT runtime·panicIndexU(SB),NOSPLIT,$0-16
+	MOVQ	AX, x+0(FP)
+	MOVQ	CX, y+8(FP)
+	JMP	runtime·goPanicIndexU(SB)
+TEXT runtime·panicSliceAlen(SB),NOSPLIT,$0-16
+	MOVQ	CX, x+0(FP)
+	MOVQ	DX, y+8(FP)
+	JMP	runtime·goPanicSliceAlen(SB)
+TEXT runtime·panicSliceAlenU(SB),NOSPLIT,$0-16
+	MOVQ	CX, x+0(FP)
+	MOVQ	DX, y+8(FP)
+	JMP	runtime·goPanicSliceAlenU(SB)
+TEXT runtime·panicSliceAcap(SB),NOSPLIT,$0-16
+	MOVQ	CX, x+0(FP)
+	MOVQ	DX, y+8(FP)
+	JMP	runtime·goPanicSliceAcap(SB)
+TEXT runtime·panicSliceAcapU(SB),NOSPLIT,$0-16
+	MOVQ	CX, x+0(FP)
+	MOVQ	DX, y+8(FP)
+	JMP	runtime·goPanicSliceAcapU(SB)
+TEXT runtime·panicSliceB(SB),NOSPLIT,$0-16
+	MOVQ	AX, x+0(FP)
+	MOVQ	CX, y+8(FP)
+	JMP	runtime·goPanicSliceB(SB)
+TEXT runtime·panicSliceBU(SB),NOSPLIT,$0-16
+	MOVQ	AX, x+0(FP)
+	MOVQ	CX, y+8(FP)
+	JMP	runtime·goPanicSliceBU(SB)
+TEXT runtime·panicSlice3Alen(SB),NOSPLIT,$0-16
+	MOVQ	DX, x+0(FP)
+	MOVQ	BX, y+8(FP)
+	JMP	runtime·goPanicSlice3Alen(SB)
+TEXT runtime·panicSlice3AlenU(SB),NOSPLIT,$0-16
+	MOVQ	DX, x+0(FP)
+	MOVQ	BX, y+8(FP)
+	JMP	runtime·goPanicSlice3AlenU(SB)
+TEXT runtime·panicSlice3Acap(SB),NOSPLIT,$0-16
+	MOVQ	DX, x+0(FP)
+	MOVQ	BX, y+8(FP)
+	JMP	runtime·goPanicSlice3Acap(SB)
+TEXT runtime·panicSlice3AcapU(SB),NOSPLIT,$0-16
+	MOVQ	DX, x+0(FP)
+	MOVQ	BX, y+8(FP)
+	JMP	runtime·goPanicSlice3AcapU(SB)
+TEXT runtime·panicSlice3B(SB),NOSPLIT,$0-16
+	MOVQ	CX, x+0(FP)
+	MOVQ	DX, y+8(FP)
+	JMP	runtime·goPanicSlice3B(SB)
+TEXT runtime·panicSlice3BU(SB),NOSPLIT,$0-16
+	MOVQ	CX, x+0(FP)
+	MOVQ	DX, y+8(FP)
+	JMP	runtime·goPanicSlice3BU(SB)
+TEXT runtime·panicSlice3C(SB),NOSPLIT,$0-16
+	MOVQ	AX, x+0(FP)
+	MOVQ	CX, y+8(FP)
+	JMP	runtime·goPanicSlice3C(SB)
+TEXT runtime·panicSlice3CU(SB),NOSPLIT,$0-16
+	MOVQ	AX, x+0(FP)
+	MOVQ	CX, y+8(FP)
+	JMP	runtime·goPanicSlice3CU(SB)