[PATCH] gdb: LoongArch: Emulate floating-point branch instructions

[PATCH] gdb: LoongArch: Emulate floating-point branch instructions

[Tiezhu Yang]

Add bceqz and bcnez cases in loongarch_insn_is_cond_branch() and
loongarch_next_pc() to emulate floating-point branch instructions.

Here are the references:

https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#_bceqz_bcnez
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#table-table-of-instruction-encoding

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 gdb/loongarch-tdep.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/gdb/loongarch-tdep.c b/gdb/loongarch-tdep.c
index 092127dd810..d79ec686e6a 100644
--- a/gdb/loongarch-tdep.c
+++ b/gdb/loongarch-tdep.c
@@ -74,7 +74,9 @@ loongarch_insn_is_cond_branch (insn_t insn)
       || (insn & 0xfc000000) == 0x68000000	/* bltu  */
       || (insn & 0xfc000000) == 0x6c000000	/* bgeu  */
       || (insn & 0xfc000000) == 0x40000000	/* beqz  */
-      || (insn & 0xfc000000) == 0x44000000)	/* bnez  */
+      || (insn & 0xfc000000) == 0x44000000	/* bnez  */
+      || (insn & 0xfc000300) == 0x48000000	/* bceqz  */
+      || (insn & 0xfc000300) == 0x48000100)	/* bcnez  */
     return true;
   return false;
 }
@@ -314,6 +316,20 @@ loongarch_next_pc (struct regcache *regcache, CORE_ADDR cur_pc)
       if (rj != 0)
 	next_pc = cur_pc + loongarch_decode_imm ("0:5|10:16<<2", insn, 1);
     }
+  else if ((insn & 0xfc000300) == 0x48000000)		/* bceqz cj, offs21  */
+    {
+      LONGEST cj = regcache_raw_get_signed (regcache,
+		     loongarch_decode_imm ("5:3", insn, 0) + LOONGARCH_FIRST_FCC_REGNUM);
+      if (cj == 0)
+	next_pc = cur_pc + loongarch_decode_imm ("0:5|10:16<<2", insn, 1);
+    }
+  else if ((insn & 0xfc000300) == 0x48000100)		/* bcnez cj, offs21  */
+    {
+      LONGEST cj = regcache_raw_get_signed (regcache,
+		     loongarch_decode_imm ("5:3", insn, 0) + LOONGARCH_FIRST_FCC_REGNUM);
+      if (cj != 0)
+	next_pc = cur_pc + loongarch_decode_imm ("0:5|10:16<<2", insn, 1);
+    }
   else if ((insn & 0xffff8000) == 0x002b0000)		/* syscall  */
     {
       if (tdep->syscall_next_pc != nullptr)
-- 
2.42.0

Re: [PATCH] gdb: LoongArch: Emulate floating-point branch instructions

[Kevin Buettner]

On Wed, 30 Apr 2025 15:10:15 +0800
Tiezhu Yang <yangtiezhu@loongson.cn> wrote:

> Add bceqz and bcnez cases in loongarch_insn_is_cond_branch() and
> loongarch_next_pc() to emulate floating-point branch instructions.
> 
> Here are the references:
> 
> https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#_bceqz_bcnez
> https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#table-table-of-instruction-encoding

Thanks for including the references, above.

The encodings for the instructions that you're handling look correct
to me.

Approved-by: Kevin Buettner <kevinb@redhat.com>

Re: [PATCH] gdb: LoongArch: Emulate floating-point branch instructions

[Tiezhu Yang]

On 5/7/25 12:30, Kevin Buettner wrote:
> On Wed, 30 Apr 2025 15:10:15 +0800
> Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
> 
>> Add bceqz and bcnez cases in loongarch_insn_is_cond_branch() and
>> loongarch_next_pc() to emulate floating-point branch instructions.
>>
>> Here are the references:
>>
>> https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#_bceqz_bcnez
>> https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#table-table-of-instruction-encoding
> 
> Thanks for including the references, above.
> 
> The encodings for the instructions that you're handling look correct
> to me.
> 
> Approved-by: Kevin Buettner <kevinb@redhat.com>

Thanks, pushed.