runtime: use the call instruction's PC for panic-in-runtime detection

If a panic happens in the runtime we turn that into a fatal error.
We use the caller's PC to determine if the panic call is inside
the runtime. getcallerpc returns the PC immediately after the
call instruction. If the call is the very last instruction of a
function, it may not find this PC belong to a runtime function,
giving false result. We need to back off the PC by 1 to the call

The gc runtime doesn't do this because the gc compiler always
emit an instruction following a panic call, presumably an UNDEF
instruction which turns into an architecture-specific illegal
instruction. Our compiler doesn't do this.

Change-Id: Iac4b5e568c9636100a5a18f737eb2a256c1ca5ca
Reviewed-by: Than McIntosh <>
Reviewed-by: Ian Lance Taylor <>
2 files changed