From patchwork Mon Oct  8 07:52:30 2012
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Subject: bug in popcnt emulation with some register operand(s)?
Date: Sun, 07 Oct 2012 21:52:30 -0000
From: malc <av1474@comtv.ru>
X-Patchwork-Id: 189928
Message-Id: <alpine.LNX.2.00.1210081152040.2993@linmac>
To: Andriy Gapon <avg@FreeBSD.org>
Cc: qemu-devel@nongnu.org

On Mon, 8 Oct 2012, Andriy Gapon wrote:

> 
> I am running Qemu (plain, no kvm, etc) on an AMD 10h machine that
> provides popcnt instruction.  Qemu advertises availability of pocnt
> to a guest as well.  What I see in the guest that popcnt
> 0x20(%r12),%r8 instruction actually placed its result into %rax.
> With %rdi and %rax operands the instruction worked fine though.
> 
> 

Does following work?


diff --git a/target-i386/translate.c b/target-i386/translate.c
index e896abf..c36cc3e 100644
--- a/target-i386/translate.c
+++ b/target-i386/translate.c
@@ -7818,7 +7818,7 @@ static target_ulong disas_insn(DisasContext *s, target_ulong pc_start)
             goto illegal_op;
 
         modrm = cpu_ldub_code(cpu_single_env, s->pc++);
-        reg = ((modrm >> 3) & 7);
+        reg = ((modrm >> 3) & 7) | rex_r;
 
         if (s->prefix & PREFIX_DATA)
             ot = OT_WORD;