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Re: [PATCH] sh4: mac.w: memory accesses are 16-bit words
From: |
Yoshinori Sato |
Subject: |
Re: [PATCH] sh4: mac.w: memory accesses are 16-bit words |
Date: |
Wed, 03 Apr 2024 15:32:55 +0900 |
User-agent: |
Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (Gojō) APEL-LB/10.8 EasyPG/1.0.0 Emacs/28.2 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) |
On Tue, 02 Apr 2024 22:26:25 +0900,
Philippe Mathieu-Daudé wrote:
>
> On 2/4/24 11:37, Zack Buhman wrote:
> > Before this change, executing a code sequence such as:
> >
> > mova tblm,r0
> > mov r0,r1
> > mova tbln,r0
> > clrs
> > clrmac
> > mac.w @r0+,@r1+
> > mac.w @r0+,@r1+
> >
> > .align 4
> > tblm: .word 0x1234
> > .word 0x5678
> > tbln: .word 0x9abc
> > .word 0xdefg
> >
> > Does not result in correct behavior:
> >
> > Expected behavior:
> > first macw : macl = 0x1234 * 0x9abc + 0x0
> > mach = 0x0
> >
> > second macw: macl = 0x5678 * 0xdefg + 0xb00a630
> > mach = 0x0
> >
> > Observed behavior (qemu-sh4eb, prior to this commit):
> >
> > first macw : macl = 0x5678 * 0xdefg + 0x0
> > mach = 0x0
> >
> > second macw: (unaligned longword memory access, SIGBUS)
> >
> > Various SH-4 ISA manuals also confirm that `mac.w` is a 16-bit word memory
> > access, not a 32-bit longword memory access.
> >
> > Signed-off-by: Zack Buhman <zack@buhman.org>
> > ---
> > target/sh4/translate.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/target/sh4/translate.c b/target/sh4/translate.c
> > index a9b1bc7524..6643c14dde 100644
> > --- a/target/sh4/translate.c
> > +++ b/target/sh4/translate.c
> > @@ -816,10 +816,10 @@ static void _decode_opc(DisasContext * ctx)
> > TCGv arg0, arg1;
> > arg0 = tcg_temp_new();
> > tcg_gen_qemu_ld_i32(arg0, REG(B7_4), ctx->memidx,
> > - MO_TESL | MO_ALIGN);
> > + MO_TESW | MO_ALIGN);
> > arg1 = tcg_temp_new();
> > tcg_gen_qemu_ld_i32(arg1, REG(B11_8), ctx->memidx,
> > - MO_TESL | MO_ALIGN);
> > + MO_TESW | MO_ALIGN);
>
> Apparently invalid since its introduction in commit fdf9b3e831.
>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>
> > gen_helper_macw(tcg_env, arg0, arg1);
> > tcg_gen_addi_i32(REG(B11_8), REG(B11_8), 2);
> > tcg_gen_addi_i32(REG(B7_4), REG(B7_4), 2);
>
SH4 Software manual said.
https://www.renesas.com/us/en/document/mas/sh-4-software-manual
> This instruction performs signed multiplication of the 16-bit operands
> whose addresses are the contents of general registers Rm and Rn,
> adds the 32-bit result to the MAC register contents, and stores the
> result in the MAC register. Operands Rm and Rn are each incremented
> by 2 each time they are read.
Reviewed-by: Yoshinori Sato <ysato@users.sourceforge.jp>
--
Yosinori Sato