target/mips/tcg/translate.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
JR opcode (Jump Register) only takes 1 argument, $rs.
JALR (Jump And Link Register) takes 3: $rs, $rd and $hint.
Commit 6af0bf9c7c3 added their processing into decode_opc() as:
case 0x08 ... 0x09: /* Jumps */
gen_compute_branch(ctx, op1 | EXT_SPECIAL, rs, rd, sa);
having both opcodes handled in the same function: gen_compute_branch.
Per JR encoding, both $rd and $hint ('sa') are decoded as zero.
Later this code got extracted to decode_opc_special(),
commit 7a387fffce5 used definitions instead of magic values:
case OPC_JR ... OPC_JALR:
gen_compute_branch(ctx, op1, rs, rd, sa);
Finally commit 0aefa33318b moved OPC_JR out of decode_opc_special,
to a new 'decode_opc_special_legacy' function:
@@ -15851,6 +15851,9 @@ static void decode_opc_special_legacy(CPUMIPSState *env, DisasContext *ctx)
+ case OPC_JR:
+ gen_compute_branch(ctx, op1, 4, rs, rd, sa);
+ break;
@@ -15933,7 +15936,7 @@ static void decode_opc_special(CPUMIPSState *env, DisasContext *ctx)
- case OPC_JR ... OPC_JALR:
+ case OPC_JALR:
gen_compute_branch(ctx, op1, 4, rs, rd, sa);
break;
Since JR is now handled individually, it is pointless to decode
and pass it unused arguments. Replace them by simple zero value
to avoid confusion with this opcode.
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
target/mips/tcg/translate.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/target/mips/tcg/translate.c b/target/mips/tcg/translate.c
index 5b03545f099..bf71724f3f0 100644
--- a/target/mips/tcg/translate.c
+++ b/target/mips/tcg/translate.c
@@ -14203,7 +14203,7 @@ static void decode_opc_special_legacy(CPUMIPSState *env, DisasContext *ctx)
break;
#endif
case OPC_JR:
- gen_compute_branch(ctx, op1, 4, rs, rd, sa, 4);
+ gen_compute_branch(ctx, op1, 4, rs, 0, 0, 4);
break;
case OPC_SPIM:
#ifdef MIPS_STRICT_STANDARD
--
2.31.1
On 7/30/21 12:55 PM, Philippe Mathieu-Daudé wrote: > case OPC_JR: > - gen_compute_branch(ctx, op1, 4, rs, rd, sa, 4); > + gen_compute_branch(ctx, op1, 4, rs, 0, 0, 4); Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~
On 7/31/21 12:55 AM, Philippe Mathieu-Daudé wrote: > JR opcode (Jump Register) only takes 1 argument, $rs. > JALR (Jump And Link Register) takes 3: $rs, $rd and $hint. > > Commit 6af0bf9c7c3 added their processing into decode_opc() as: > > case 0x08 ... 0x09: /* Jumps */ > gen_compute_branch(ctx, op1 | EXT_SPECIAL, rs, rd, sa); > > having both opcodes handled in the same function: gen_compute_branch. > > Per JR encoding, both $rd and $hint ('sa') are decoded as zero. > > Later this code got extracted to decode_opc_special(), > commit 7a387fffce5 used definitions instead of magic values: > > case OPC_JR ... OPC_JALR: > gen_compute_branch(ctx, op1, rs, rd, sa); > > Finally commit 0aefa33318b moved OPC_JR out of decode_opc_special, > to a new 'decode_opc_special_legacy' function: > > @@ -15851,6 +15851,9 @@ static void decode_opc_special_legacy(CPUMIPSState *env, DisasContext *ctx) > + case OPC_JR: > + gen_compute_branch(ctx, op1, 4, rs, rd, sa); > + break; > > @@ -15933,7 +15936,7 @@ static void decode_opc_special(CPUMIPSState *env, DisasContext *ctx) > - case OPC_JR ... OPC_JALR: > + case OPC_JALR: > gen_compute_branch(ctx, op1, 4, rs, rd, sa); > break; > > Since JR is now handled individually, it is pointless to decode > and pass it unused arguments. Replace them by simple zero value > to avoid confusion with this opcode. > > Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org> > --- > target/mips/tcg/translate.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Thanks, applied to mips-next.
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