Re: [Qemu-devel] [7042] target-mips: optimize decode_opc()

[Aurelien Jarno]

On Sun, Apr 12, 2009 at 10:14:56PM +0200, Stefan Weil wrote:
> Aurelien Jarno schrieb:
> > Revision: 7042
> > http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=7042
> > Author: aurel32
> > Date: 2009-04-08 21:47:55 +0000 (Wed, 08 Apr 2009)
> > Log Message:
> > -----------
> > target-mips: optimize decode_opc()
> >
> > Signed-off-by: Aurelien Jarno <address@hidden>
> >
> > Modified Paths:
> > --------------
> > trunk/target-mips/translate.c
> >
> > Modified: trunk/target-mips/translate.c
> > ===================================================================
> > --- trunk/target-mips/translate.c 2009-04-08 21:47:44 UTC (rev 7041)
> > +++ trunk/target-mips/translate.c 2009-04-08 21:47:55 UTC (rev 7042)
> > @@ -7527,7 +7527,6 @@
> > case OPC_MOVCI:
> > check_insn(env, ctx, ISA_MIPS4 | ISA_MIPS32);
> > if (env->CP0_Config1 & (1 << CP0C1_FP)) {
> > - save_cpu_state(ctx, 1);
> > check_cp1_enabled(ctx);
> > gen_movci(ctx, rd, rs, (ctx->opcode >> 18) & 0x7,
> > (ctx->opcode >> 16) & 1);
> > @@ -7623,28 +7622,33 @@
> > case OPC_RDHWR:
> > check_insn(env, ctx, ISA_MIPS32R2);
> > {
> > - TCGv t0 = tcg_temp_local_new();
> > + TCGv t0 = tcg_temp_new();
> >
> > switch (rd) {
> > case 0:
> > save_cpu_state(ctx, 1);
> > gen_helper_rdhwr_cpunum(t0);
> > + gen_store_gpr(t0, rt);
> > break;
> > case 1:
> > save_cpu_state(ctx, 1);
> > gen_helper_rdhwr_synci_step(t0);
> > + gen_store_gpr(t0, rt);
> > break;
> > case 2:
> > save_cpu_state(ctx, 1);
> > gen_helper_rdhwr_cc(t0);
> > + gen_store_gpr(t0, rt);
> > break;
> > case 3:
> > save_cpu_state(ctx, 1);
> > gen_helper_rdhwr_ccres(t0);
> > + gen_store_gpr(t0, rt);
> > break;
> > case 29:
> > #if defined(CONFIG_USER_ONLY)
> > tcg_gen_ld_tl(t0, cpu_env, offsetof(CPUState, tls_value));
> > + gen_store_gpr(t0, rt);
> > break;
> > #else
> > /* XXX: Some CPUs implement this in hardware.
> > @@ -7655,15 +7659,14 @@
> > generate_exception(ctx, EXCP_RI);
> > break;
> > }
> > - gen_store_gpr(t0, rt);
> > tcg_temp_free(t0);
> > }
> > break;
> > case OPC_FORK:
> > check_insn(env, ctx, ASE_MT);
> > {
> > - TCGv t0 = tcg_temp_local_new();
> > - TCGv t1 = tcg_temp_local_new();
> > + TCGv t0 = tcg_temp_new();
> > + TCGv t1 = tcg_temp_new();
> >
> > gen_load_gpr(t0, rt);
> > gen_load_gpr(t1, rs);
> > @@ -7675,8 +7678,9 @@
> > case OPC_YIELD:
> > check_insn(env, ctx, ASE_MT);
> > {
> > - TCGv t0 = tcg_temp_local_new();
> > + TCGv t0 = tcg_temp_new();
> >
> > + save_cpu_state(ctx, 1);
> > gen_load_gpr(t0, rs);
> > gen_helper_yield(t0, t0);
> > gen_store_gpr(t0, rd);
> > @@ -7748,37 +7752,41 @@
> > case OPC_MFMC0:
> > #ifndef CONFIG_USER_ONLY
> > {
> > - TCGv t0 = tcg_temp_local_new();
> > + TCGv t0 = tcg_temp_new();
> >
> > op2 = MASK_MFMC0(ctx->opcode);
> > switch (op2) {
> > case OPC_DMT:
> > check_insn(env, ctx, ASE_MT);
> > gen_helper_dmt(t0, t0);
> > + gen_store_gpr(t0, rt);
> > break;
> > case OPC_EMT:
> > check_insn(env, ctx, ASE_MT);
> > gen_helper_emt(t0, t0);
> > + gen_store_gpr(t0, rt);
> > break;
> > case OPC_DVPE:
> > check_insn(env, ctx, ASE_MT);
> > gen_helper_dvpe(t0, t0);
> > + gen_store_gpr(t0, rt);
> > break;
> > case OPC_EVPE:
> > check_insn(env, ctx, ASE_MT);
> > gen_helper_evpe(t0, t0);
> > + gen_store_gpr(t0, rt);
> > break;
> > case OPC_DI:
> > check_insn(env, ctx, ISA_MIPS32R2);
> > - save_cpu_state(ctx, 1);
> save_cpu_state needed?
> > gen_helper_di(t0);
> > + gen_store_gpr(t0, rt);
> > /* Stop translation as we may have switched the execution mode */
> > ctx->bstate = BS_STOP;
> > break;
> > case OPC_EI:
> > check_insn(env, ctx, ISA_MIPS32R2);
> > - save_cpu_state(ctx, 1);
> save_cpu_state needed?
> > gen_helper_ei(t0);
> > + gen_store_gpr(t0, rt);
> > /* Stop translation as we may have switched the execution mode */
> > ctx->bstate = BS_STOP;
> > break;
> > @@ -7787,7 +7795,6 @@
> > generate_exception(ctx, EXCP_RI);
> > break;
> > }
> > - gen_store_gpr(t0, rt);
> > tcg_temp_free(t0);
> > }
> > #endif /* !CONFIG_USER_ONLY */
> > @@ -7839,7 +7846,6 @@
> > case OPC_SWC1:
> > case OPC_SDC1:
> > if (env->CP0_Config1 & (1 << CP0C1_FP)) {
> > - save_cpu_state(ctx, 1);
> > check_cp1_enabled(ctx);
> > gen_flt_ldst(ctx, op, rt, rs, imm);
> > } else {
> > @@ -7849,7 +7855,6 @@
> >
> > case OPC_CP1:
> > if (env->CP0_Config1 & (1 << CP0C1_FP)) {
> > - save_cpu_state(ctx, 1);
> > check_cp1_enabled(ctx);
> > op1 = MASK_CP1(ctx->opcode);
> > switch (op1) {
> > @@ -7908,7 +7913,6 @@
> >
> > case OPC_CP3:
> > if (env->CP0_Config1 & (1 << CP0C1_FP)) {
> > - save_cpu_state(ctx, 1);
> > check_cp1_enabled(ctx);
> > op1 = MASK_CP3(ctx->opcode);
> > switch (op1) {
> >
> 
> This patch breaks Linux boot (fatal kernel error during boot,
> wrong kernel mode?). I'm sorry that I cannot give more
> details at the moment because I have trouble with
> my test hardware.
> 
> Tested with QEMU trunk, mips little endian, malta machine.
> 
> Re-adding the two removed calls of save_cpu_state (for
> OPC_DI, OPC_EI) lets the kernel boot again.
> Maybe there is a better fix.
> 

Reverting those parts is actually the correct fix. I have remove the
calls to save_cpu_states() for helpers that can't trigger an exception,
but I forget to consider the case where those helpers are rising an
interrupt, calling in fine cpu_unlink_tb().

Strangely my test image was still working here, probably because I only
tried with a kernel without R2 support.

That should be fixed in the SVN now.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net