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Re: Patch: -Wunreachable-bytecode

From: Per Bothner <per at bothner dot com>
To: tromey at redhat dot com
Cc: Java Patch List <java-patches at gcc dot gnu dot org>, Gcc Patch List<gcc-patches at gcc dot gnu dot org>
Date: Tue, 18 Jun 2002 22:41:55 -0700
Subject: Re: Patch: -Wunreachable-bytecode
References: <87bsac1hih.fsf@fleche.redhat.com> <3D0CF38B.4080100@bothner.com> <87bsabyn0i.fsf@fleche.redhat.com>

Tom Tromey wrote:

"Per" == Per Bothner <per@bothner.com> writes:

Per> Why do we want to supress it?  Is it unreachable bytecode in
Per> .class files generated by gcj?

Yes.  The appended file causes gcj to emit an unused instruction.

The "unreachable bytecode" contains a single goto.  I'm guessing this
is a side effect of your recent goto-to-goto optimization.  I.e.

 47: goto 52
 50: iconst_0
 51: ireturn
 52: goto 69

got optimized to:

 47: goto 69
 50: iconst_0
 51: ireturn
 52: goto 69

and now instruction 52 is unreachable.

One solution may be reference counting the blocks.
--
	--Per Bothner
per@bothner.com   http://www.bothner.com/per/

References:
- Patch: -Wunreachable-bytecode
  - From: Tom Tromey
- Re: Patch: -Wunreachable-bytecode
  - From: Per Bothner
- Re: Patch: -Wunreachable-bytecode
  - From: Tom Tromey

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