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Re: TARGET_SHIFT_TRUNCATION_MASK

From: Paolo Bonzini <bonzini at gnu dot org>
To: Uros Bizjak <ubizjak at gmail dot com>
Cc: GCC Mailing List <gcc at gcc dot gnu dot org>
Date: Fri, 16 Jul 2010 09:38:06 +0200
Subject: Re: TARGET_SHIFT_TRUNCATION_MASK
References: <AANLkTik5oABbPZOAXbbRn8ylfbeJiFPo7Hk0uP7njPSK@mail.gmail.com> <4C3EFC37.50303@gnu.org> <AANLkTimIHCLO_vDXMsgFWFwKowwQSmRx1GliBYwxzLGZ@mail.gmail.com>

On 07/15/2010 02:26 PM, Uros Bizjak wrote:

The reason you pointed out is for SHIFT_COUNT_TRUNCATED. Please note,
that we don't use memory_operands, but even in register operand case,
"bt" insn doesn't truncate the bit-count operand, but performs modulo
operation on it. I.E, "bt %reg, 75" will not return 0, but shift insn
with the same operands will.

Yes, only for memory_operands.

You can take a look at the attached patch. I never got round to finish it, but I think it bootstrapped. It unifies SHIFT_COUNT_TRUNCATED and TARGET_SHIFT_TRUNCATION_MASK, I think it can be useful for x86.

Paolo

Attachment: for-uros.patch
Description: Text document

References:
- TARGET_SHIFT_TRUNCATION_MASK
  - From: Uros Bizjak
- Re: TARGET_SHIFT_TRUNCATION_MASK
  - From: Paolo Bonzini
- Re: TARGET_SHIFT_TRUNCATION_MASK
  - From: Uros Bizjak

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