Re: [PATCH] Hexagon: lldb read/write predicate registers p0/p1/p2/p3

[Brian Cain]

On 6/12/2024 11:42 AM, Taylor Simpson wrote:
> hexagon-core.xml only exposes register p3_0 which is an alias that
> aggregates the predicate registers.  It is more convenient for users
> to interact directly with the predicate registers.
>
> Tested with lldb downloaded from this location
> https://github.com/llvm/llvm-project/releases/download/llvmorg-18.1.4/clang+llvm-18.1.4-x86_64-linux-gnu-ubuntu-18.04.tar.xz
>
> BEFORE:
> (lldb) reg read p3_0
>      p3_0 = 0x00000000
> (lldb) reg read p0
> error: Invalid register name 'p0'.
> (lldb) reg write p1 0xf
> error: Register not found for 'p1'.
>
> AFTER:
> (lldb) reg read p3_0
>      p3_0 = 0x00000000
> (lldb) reg read p0
>        p0 = 0x00
> (lldb) reg read -s 1
> Predicate Registers:
>          p0 = 0x00
>          p1 = 0x00
>          p2 = 0x00
>          p3 = 0x00
>
> (lldb) reg write p1 0xf
> (lldb) reg read p3_0
>      p3_0 = 0x00000f00
> (lldb) reg write p3_0 0xff00ff00
> (lldb) reg read -s 1
> Predicate Registers:
>          p0 = 0x00
>          p1 = 0xff
>          p2 = 0x00
>          p3 = 0xff
>
> Signed-off-by: Taylor Simpson <ltaylorsimpson@gmail.com>
> ---


Queued.  Thanks!


>   target/hexagon/gdbstub.c | 19 ++++++++++++++++++-
>   gdb-xml/hexagon-core.xml |  6 +++++-
>   2 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/target/hexagon/gdbstub.c b/target/hexagon/gdbstub.c
> index 502c6987f0..e67e627fc9 100644
> --- a/target/hexagon/gdbstub.c
> +++ b/target/hexagon/gdbstub.c
> @@ -1,5 +1,5 @@
>   /*
> - *  Copyright(c) 2019-2021 Qualcomm Innovation Center, Inc. All Rights 
> Reserved.
> + *  Copyright(c) 2019-2024 Qualcomm Innovation Center, Inc. All Rights 
> Reserved.
>    *
>    *  This program is free software; you can redistribute it and/or modify
>    *  it under the terms of the GNU General Public License as published by
> @@ -36,6 +36,14 @@ int hexagon_gdb_read_register(CPUState *cs, GByteArray 
> *mem_buf, int n)
>           return gdb_get_regl(mem_buf, env->gpr[n]);
>       }
>   
> +    n -= TOTAL_PER_THREAD_REGS;
> +
> +    if (n < NUM_PREGS) {
> +        return gdb_get_reg8(mem_buf, env->pred[n]);
> +    }
> +
> +    n -= NUM_PREGS;
> +
>       g_assert_not_reached();
>   }
>   
> @@ -56,6 +64,15 @@ int hexagon_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
>           return sizeof(target_ulong);
>       }
>   
> +    n -= TOTAL_PER_THREAD_REGS;
> +
> +    if (n < NUM_PREGS) {
> +        env->pred[n] = ldtul_p(mem_buf);
> +        return sizeof(uint8_t);
> +    }
> +
> +    n -= NUM_PREGS;
> +
>       g_assert_not_reached();
>   }
>   
> diff --git a/gdb-xml/hexagon-core.xml b/gdb-xml/hexagon-core.xml
> index e181163cff..b94378112a 100644
> --- a/gdb-xml/hexagon-core.xml
> +++ b/gdb-xml/hexagon-core.xml
> @@ -1,6 +1,6 @@
>   <?xml version="1.0"?>
>   <!--
> -  Copyright(c) 2023 Qualcomm Innovation Center, Inc. All Rights Reserved.
> +  Copyright(c) 2023-2024 Qualcomm Innovation Center, Inc. All Rights Reserved.
>   
>     This work is licensed under the terms of the GNU GPL, version 2 or
>     (at your option) any later version. See the COPYING file in the
> @@ -80,5 +80,9 @@
>     <reg name="c29"              bitsize="32" offset="244" encoding="uint" format="hex" 
> group="Thread Registers" dwarf_regnum="61"/>
>     <reg name="utimerlo"         bitsize="32" offset="248" encoding="uint" format="hex" 
> group="Thread Registers" dwarf_regnum="62"/>
>     <reg name="utimerhi"         bitsize="32" offset="252" encoding="uint" format="hex" 
> group="Thread Registers" dwarf_regnum="63"/>
> +  <reg name="p0"               bitsize="8"  offset="256" encoding="uint" format="hex" 
> group="Predicate Registers" dwarf_regnum="64"/>
> +  <reg name="p1"               bitsize="8"  offset="257" encoding="uint" format="hex" 
> group="Predicate Registers" dwarf_regnum="65"/>
> +  <reg name="p2"               bitsize="8"  offset="258" encoding="uint" format="hex" 
> group="Predicate Registers" dwarf_regnum="66"/>
> +  <reg name="p3"               bitsize="8"  offset="259" encoding="uint" format="hex" 
> group="Predicate Registers" dwarf_regnum="67"/>
>   
>   </feature>