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Re: [Qemu-devel] [PATCH v2 5/6] tcg/mips: Support r6 multiply/divide enc


From: Richard Henderson
Subject: Re: [Qemu-devel] [PATCH v2 5/6] tcg/mips: Support r6 multiply/divide encodings
Date: Fri, 2 Oct 2015 05:40:26 +1000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0

On 10/01/2015 08:58 PM, James Hogan wrote:
MIPSr6 adds several new integer multiply, divide, and modulo
instructions, and removes several pre-r6 encodings, along with the HI/LO
registers which were the implicit operands of some of those
instructions. Update TCG to use the new instructions when built for r6.

The new instructions actually map much more directly to the TCG ops, as
they only provide a single 32-bit half of the result and in a normal
general purpose register instead of HI or LO.

The mulu2_i32 and muls2_i32 operations are no longer appropriate for r6,
so they are removed from the TCG opcode table. This is because they
would need to emit two separate host instructions anyway (for the high
and low half of the result), which TCG can arrange automatically for us
in the absense of mulu2_i32/muls2_i32 by splitting it into mul_i32 and
mul*h_i32 TCG ops.

Signed-off-by: James Hogan<address@hidden>
Cc: Richard Henderson<address@hidden>
Cc: Aurelien Jarno<address@hidden>
---
Changes in v2:
- Use a common OPC_MUL definition. use_mips32_instructions will always
   be 1 for MIPS r6 builds (Richard)
---

Reviewed-by: Richard Henderson <address@hidden>


r~



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