Re: [PATCH v5 06/15] target/riscv: zicfilp `lpad` impl and branch tracking

[Richard Henderson]

On 8/20/24 10:01, Deepak Gupta wrote:
> Implements setting lp expected when `jalr` is encountered and implements
> `lpad` instruction of zicfilp. `lpad` instruction is taken out of
> auipc x0, <imm_20>. This is an existing HINTNOP space. If `lpad` is
> target of an indirect branch, cpu checks for 20 bit value in x7 upper
> with 20 bit value embedded in `lpad`. If they don't match, cpu raises a
> sw check exception with tval = 2.
>
> Signed-off-by: Deepak Gupta <debug@rivosinc.com>
> Co-developed-by: Jim Shu <jim.shu@sifive.com>
> Co-developed-by: Andy Chiu <andy.chiu@sifive.com>
> ---
>   target/riscv/cpu_user.h                 |  1 +
>   target/riscv/insn32.decode              |  5 ++-
>   target/riscv/insn_trans/trans_rvi.c.inc | 55 +++++++++++++++++++++++++
>   3 files changed, 60 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/cpu_user.h b/target/riscv/cpu_user.h
> index 02afad608b..e6927ff847 100644
> --- a/target/riscv/cpu_user.h
> +++ b/target/riscv/cpu_user.h
> @@ -15,5 +15,6 @@
>   #define xA6 16
>   #define xA7 17  /* syscall number for RVI ABI */
>   #define xT0 5   /* syscall number for RVE ABI */
> +#define xT2 7
>   
>   #endif
> diff --git a/target/riscv/insn32.decode b/target/riscv/insn32.decode
> index c45b8fa1d8..6533cb0758 100644
> --- a/target/riscv/insn32.decode
> +++ b/target/riscv/insn32.decode
> @@ -123,7 +123,10 @@ sfence_vm   0001000    00100 ..... 000 00000 1110011 
> @sfence_vm
>   
>   # *** RV32I Base Instruction Set ***
>   lui      ....................       ..... 0110111 @u
> -auipc    ....................       ..... 0010111 @u
> +{
> +  lpad     label:20                   00000 0010111
> +  auipc    ....................       ..... 0010111 @u
> +}
>   jal      ....................       ..... 1101111 @j

Again, best to line up the decode bits.

While you are required to add two spaces within { },
you can remove two spaces before the first '.':

lui      ....................       ..... 0110111 @u
{
  lpad   label:20                   00000 0010111
  auipc  ....................       ..... 0010111 @u
}
jal      ....................       ..... 1101111 @j


Otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~