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_s390x.s b/src/runtime/asm_s390x.s
index 566c3e9236..5b9e0cd481 100644
--- a/src/runtime/asm_s390x.s
+++ b/src/runtime/asm_s390x.s
@@ -863,3 +863,73 @@ flush:
 	MOVD	24(R15), R0      // restore R0
 	LMG	32(R15), R5, R12 // restore R5 - R12
 	JMP	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
+	MOVD	R0, x+0(FP)
+	MOVD	R1, y+8(FP)
+	JMP	runtime·goPanicIndex(SB)
+TEXT runtime·panicIndexU(SB),NOSPLIT,$0-16
+	MOVD	R0, x+0(FP)
+	MOVD	R1, y+8(FP)
+	JMP	runtime·goPanicIndexU(SB)
+TEXT runtime·panicSliceAlen(SB),NOSPLIT,$0-16
+	MOVD	R1, x+0(FP)
+	MOVD	R2, y+8(FP)
+	JMP	runtime·goPanicSliceAlen(SB)
+TEXT runtime·panicSliceAlenU(SB),NOSPLIT,$0-16
+	MOVD	R1, x+0(FP)
+	MOVD	R2, y+8(FP)
+	JMP	runtime·goPanicSliceAlenU(SB)
+TEXT runtime·panicSliceAcap(SB),NOSPLIT,$0-16
+	MOVD	R1, x+0(FP)
+	MOVD	R2, y+8(FP)
+	JMP	runtime·goPanicSliceAcap(SB)
+TEXT runtime·panicSliceAcapU(SB),NOSPLIT,$0-16
+	MOVD	R1, x+0(FP)
+	MOVD	R2, y+8(FP)
+	JMP	runtime·goPanicSliceAcapU(SB)
+TEXT runtime·panicSliceB(SB),NOSPLIT,$0-16
+	MOVD	R0, x+0(FP)
+	MOVD	R1, y+8(FP)
+	JMP	runtime·goPanicSliceB(SB)
+TEXT runtime·panicSliceBU(SB),NOSPLIT,$0-16
+	MOVD	R0, x+0(FP)
+	MOVD	R1, y+8(FP)
+	JMP	runtime·goPanicSliceBU(SB)
+TEXT runtime·panicSlice3Alen(SB),NOSPLIT,$0-16
+	MOVD	R2, x+0(FP)
+	MOVD	R3, y+8(FP)
+	JMP	runtime·goPanicSlice3Alen(SB)
+TEXT runtime·panicSlice3AlenU(SB),NOSPLIT,$0-16
+	MOVD	R2, x+0(FP)
+	MOVD	R3, y+8(FP)
+	JMP	runtime·goPanicSlice3AlenU(SB)
+TEXT runtime·panicSlice3Acap(SB),NOSPLIT,$0-16
+	MOVD	R2, x+0(FP)
+	MOVD	R3, y+8(FP)
+	JMP	runtime·goPanicSlice3Acap(SB)
+TEXT runtime·panicSlice3AcapU(SB),NOSPLIT,$0-16
+	MOVD	R2, x+0(FP)
+	MOVD	R3, y+8(FP)
+	JMP	runtime·goPanicSlice3AcapU(SB)
+TEXT runtime·panicSlice3B(SB),NOSPLIT,$0-16
+	MOVD	R1, x+0(FP)
+	MOVD	R2, y+8(FP)
+	JMP	runtime·goPanicSlice3B(SB)
+TEXT runtime·panicSlice3BU(SB),NOSPLIT,$0-16
+	MOVD	R1, x+0(FP)
+	MOVD	R2, y+8(FP)
+	JMP	runtime·goPanicSlice3BU(SB)
+TEXT runtime·panicSlice3C(SB),NOSPLIT,$0-16
+	MOVD	R0, x+0(FP)
+	MOVD	R1, y+8(FP)
+	JMP	runtime·goPanicSlice3C(SB)
+TEXT runtime·panicSlice3CU(SB),NOSPLIT,$0-16
+	MOVD	R0, x+0(FP)
+	MOVD	R1, y+8(FP)
+	JMP	runtime·goPanicSlice3CU(SB)