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Date: Fri, 13 Feb 2009 22:30:27 +0200
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From: Blue Swirl <blauwirbel@gmail.com>
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Subject: [Qemu-devel] PPC debugging broken
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To: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

It looks like debugging confuses PPC branch code generation.

For example, I'm doing single stepping from GDB:
IN: cmdline_prompt
0xfff158a0:  b       0xfff15960
(Unconditional branch to 0xfff15960)
OP:
 movi_i32 nip,$0xfff15960
(OK, branch)
 movi_i32 nip,$0xfff158a4
(WTF?)
 movi_i32 tmp0,$0x10002
 movi_i64 tmp1,$raise_exception
 call tmp1,$0x0,$0,tmp0
 exit_tb $0x0

(Execution continues on $nip + 4 instead of branch target)
IN: cmdline_prompt
0xfff158a4:  lis     r9,-12

OP:
 movi_i32 r9,$0xfff40000
 movi_i32 nip,$0xfff158a8
 movi_i32 nip,$0xfff158a8
 movi_i32 tmp0,$0x10002
 movi_i64 tmp1,$raise_exception
 call tmp1,$0x0,$0,tmp0
 exit_tb $0x0