Re: [Qemu-devel] [PATCH] PPC: Introduce 32bit only cmp ops

[Alexander Graf <agraf@suse.de>]

On 08.05.2013, at 12:29, Aurelien Jarno wrote:

> On Wed, May 08, 2013 at 12:06:52PM +0200, Alexander Graf wrote:
>> When running a 32bit target CPU with qemu-(system-)-ppc, NARROW_MODE
>> is not set, so we never get to leverage the "32bit only" code path in
>> the compare op handlers.
>> 
>> Introduce new handlers based on the 32bit only flag. That way we can
>> have 2 separate functions for 32bit mode and 64bit mode, which can
>> handle NARROW_MODE.
>> 
>> Reported-by: Torbjorn Granlund <tg@gmplib.org>
>> Signed-off-by: Alexander Graf <agraf@suse.de>
>> ---
>> target-ppc/translate.c |   48 ++++++++++++++++++++++++++++++++++++++++--------
>> 1 files changed, 40 insertions(+), 8 deletions(-)
>> 
>> diff --git a/target-ppc/translate.c b/target-ppc/translate.c
>> index a018616..002f9ae 100644
>> --- a/target-ppc/translate.c
>> +++ b/target-ppc/translate.c
>> @@ -675,7 +675,7 @@ static inline void gen_set_Rc0(DisasContext *ctx, TCGv reg)
>> /* cmp */
>> static void gen_cmp(DisasContext *ctx)
>> {
>> -    if (NARROW_MODE(ctx) || !(ctx->opcode & 0x00200000)) {
>> +    if (!(ctx->opcode & 0x00200000)) {
>>         gen_op_cmp32(cpu_gpr[rA(ctx->opcode)], cpu_gpr[rB(ctx->opcode)],
>>                      1, crfD(ctx->opcode));
>>     } else {
>> @@ -684,10 +684,17 @@ static void gen_cmp(DisasContext *ctx)
>>     }
>> }
>> 
>> +/* cmp 32bit only */
>> +static void gen_cmp32(DisasContext *ctx)
>> +{
>> +    gen_op_cmp32(cpu_gpr[rA(ctx->opcode)], cpu_gpr[rB(ctx->opcode)],
>> +                 1, crfD(ctx->opcode));
>> +}
>> +
>> /* cmpi */
>> static void gen_cmpi(DisasContext *ctx)
>> {
>> -    if (NARROW_MODE(ctx) || !(ctx->opcode & 0x00200000)) {
>> +    if (!(ctx->opcode & 0x00200000)) {
>>         gen_op_cmpi32(cpu_gpr[rA(ctx->opcode)], SIMM(ctx->opcode),
>>                       1, crfD(ctx->opcode));
>>     } else {
>> @@ -696,10 +703,17 @@ static void gen_cmpi(DisasContext *ctx)
>>     }
>> }
>> 
>> +/* cmpi 32bit only */
>> +static void gen_cmpi32(DisasContext *ctx)
>> +{
>> +    gen_op_cmpi32(cpu_gpr[rA(ctx->opcode)], SIMM(ctx->opcode),
>> +                  1, crfD(ctx->opcode));
>> +}
>> +
>> /* cmpl */
>> static void gen_cmpl(DisasContext *ctx)
>> {
>> -    if (NARROW_MODE(ctx) || !(ctx->opcode & 0x00200000)) {
>> +    if (!(ctx->opcode & 0x00200000)) {
>>         gen_op_cmp32(cpu_gpr[rA(ctx->opcode)], cpu_gpr[rB(ctx->opcode)],
>>                      0, crfD(ctx->opcode));
>>     } else {
>> @@ -708,10 +722,17 @@ static void gen_cmpl(DisasContext *ctx)
>>     }
>> }
>> 
>> +/* cmpl 32bit only */
>> +static void gen_cmpl32(DisasContext *ctx)
>> +{
>> +    gen_op_cmp32(cpu_gpr[rA(ctx->opcode)], cpu_gpr[rB(ctx->opcode)],
>> +                 0, crfD(ctx->opcode));
>> +}
>> +
>> /* cmpli */
>> static void gen_cmpli(DisasContext *ctx)
>> {
>> -    if (NARROW_MODE(ctx) || !(ctx->opcode & 0x00200000)) {
>> +    if (!(ctx->opcode & 0x00200000)) {
>>         gen_op_cmpi32(cpu_gpr[rA(ctx->opcode)], UIMM(ctx->opcode),
>>                       0, crfD(ctx->opcode));
>>     } else {
>> @@ -720,6 +741,13 @@ static void gen_cmpli(DisasContext *ctx)
>>     }
>> }
>> 
>> +/* cmpli 32bit only */
>> +static void gen_cmpli32(DisasContext *ctx)
>> +{
>> +    gen_op_cmpi32(cpu_gpr[rA(ctx->opcode)], UIMM(ctx->opcode),
>> +                  0, crfD(ctx->opcode));
>> +}
>> +
>> /* isel (PowerPC 2.03 specification) */
>> static void gen_isel(DisasContext *ctx)
>> {
>> @@ -8638,10 +8666,14 @@ GEN_SPE(efdtsteq,  speundef,  0x1F, 0x0B, 0x00600000, 0xFFFFFFFF, PPC_SPE_DOUBLE
>> 
>> static opcode_t opcodes[] = {
>> GEN_HANDLER(invalid, 0x00, 0x00, 0x00, 0xFFFFFFFF, PPC_NONE),
>> -GEN_HANDLER(cmp, 0x1F, 0x00, 0x00, 0x00400000, PPC_INTEGER),
>> -GEN_HANDLER(cmpi, 0x0B, 0xFF, 0xFF, 0x00400000, PPC_INTEGER),
>> -GEN_HANDLER(cmpl, 0x1F, 0x00, 0x01, 0x00400000, PPC_INTEGER),
>> -GEN_HANDLER(cmpli, 0x0A, 0xFF, 0xFF, 0x00400000, PPC_INTEGER),
>> +GEN_HANDLER(cmp, 0x1F, 0x00, 0x00, 0x00400000, PPC_64B),
>> +GEN_HANDLER_E(cmp32, 0x1F, 0x00, 0x00, 0x00400000, PPC_NONE, PPC2_32B),
> 
> You have to declare the L bit as invalid, so that trying to execute a
> 64-bit cmp* instruction on a 32-bit CPU causes an invalid instruction
> exception.

You're right. I wanted to verify it against a real 32bit system first. It does indeed treat the L bit as reserved. Then we can simply remove the 32bit only variant handlers and only use the opcode table for the reserved bits.


Alex