From: Vince Weaver <vince@csl.cornell.edu>
To: qemu-devel@nongnu.org
Subject: re: [Qemu-devel] [5283] Use the new concat_tl_i64 op for std and stda
Date: Tue, 23 Sep 2008 17:49:13 -0400 (EDT) [thread overview]
Message-ID: <20080923174506.X10311@stanley.csl.cornell.edu> (raw)
Hello
the aforementioned patch broke the spec2k crafty benchmark on
sparc32plus-linux-user (I'm running on x86_64 but I don't think it makes a
difference).
As always, the problem is when there are high bits (above 32) set when
concating.
The old code generated:
mov_i32 tmp11,tmp0
mov_i32 tmp1,loc4
movi_i64 tmp12,$0xffffffff
and_i64 tmp10,tmp1,tmp12
movi_i64 tmp12,$0x20
shl_i64 tmp10,tmp10,tmp12
movi_i64 tmp12,$0xffffffff
and_i64 tmp2,tmp11,tmp12
or_i64 tmp2,tmp2,tmp10
qemu_st64 tmp2,loc5,$0x0
The new code generates:
movi_i64 tmp12,$0x20
shl_i64 tmp10,loc4,tmp12
or_i64 tmp2,tmp0,tmp10
qemu_st64 tmp2,loc5,$0x0
which generates wrong values because the low value being concatenated
isn't masked/truncated to 32-bits first.
Vince
next reply other threads:[~2008-09-23 21:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-23 21:49 Vince Weaver [this message]
2008-09-23 21:59 ` [Qemu-devel] [5283] Use the new concat_tl_i64 op for std and stda Paul Brook
2008-09-23 22:08 ` Vince Weaver
2008-09-23 22:31 ` Vince Weaver
2008-09-23 22:31 ` Paul Brook
-- strict thread matches above, loose matches on Subject: below --
2008-09-21 18:43 Blue Swirl
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