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Re: [Qemu-devel] [PATCH] tcg/arm: Fix double-word comparisons
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From: |
Richard Henderson |
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Subject: |
Re: [Qemu-devel] [PATCH] tcg/arm: Fix double-word comparisons |
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Date: |
Mon, 15 Jan 2018 09:31:43 -0800 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 |
On 01/15/2018 06:27 AM, Peter Maydell wrote:
> We could avoid the annoying "load LE/GE immediates to tempreg"
> extra code by having tcg_out_cmp2() return a flag to tell
> the caller which way round to put the conditions for its two
> conditional ARITH_MOV insns (for setcond2) or which condition
> to use for the branch (brcond2), right?
No.
We do return a condition to use for the user. When we do the LE/GT load
immediates to temp path, we do apply tcg_cond_swap(cond), which converts the
condition as for swapped arguments, i.e. to GE/LT.
But we can't *not* swap the arguments to the generated comparison. Otherwise
we're computing the wrong thing.
r~