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target/microblaze: Split out MSR[C] to its own variable
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Having the MSR[C] bit separate will improve arithmetic that operates
on the carry bit.  Having mb_cpu_read_msr() populate MSR[CC] will
prevent the carry copy not matching the carry bit.

Tested-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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@rth7680
rth7680 committed Sep 1, 2020
1 parent 480d29a commit 1074c0f
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Showing 6 changed files with 82 additions and 96 deletions.
2 changes: 1 addition & 1 deletion linux-user/elfload.c
View file
Expand Up @@ -1039,7 +1039,7 @@ static void elf_core_copy_regs(target_elf_gregset_t *regs, const CPUMBState *env
}

(*regs)[pos++] = tswapreg(env->pc);
(*regs)[pos++] = tswapreg(env->msr);
(*regs)[pos++] = tswapreg(mb_cpu_read_msr(env));
(*regs)[pos++] = 0;
(*regs)[pos++] = tswapreg(env->ear);
(*regs)[pos++] = 0;
Expand Down
4 changes: 2 additions & 2 deletions target/microblaze/cpu.c
View file
Expand Up @@ -121,9 +121,9 @@ static void mb_cpu_reset(DeviceState *dev)

#if defined(CONFIG_USER_ONLY)
/* start in user mode with interrupts enabled. */
env->msr = MSR_EE | MSR_IE | MSR_VM | MSR_UM;
mb_cpu_write_msr(env, MSR_EE | MSR_IE | MSR_VM | MSR_UM);
#else
env->msr = 0;
mb_cpu_write_msr(env, 0);
mmu_init(&env->mmu);
env->mmu.c_mmu = 3;
env->mmu.c_mmu_tlb_access = 3;
Expand Down
19 changes: 18 additions & 1 deletion target/microblaze/cpu.h
View file
Expand Up @@ -236,7 +236,8 @@ struct CPUMBState {
uint32_t imm;
uint32_t regs[32];
uint32_t pc;
uint32_t msr;
uint32_t msr; /* All bits of MSR except MSR[C] and MSR[CC] */
uint32_t msr_c; /* MSR[C], in low bit; other bits must be 0 */
uint64_t ear;
uint32_t esr;
uint32_t fsr;
Expand Down Expand Up @@ -327,6 +328,22 @@ hwaddr mb_cpu_get_phys_page_debug(CPUState *cpu, vaddr addr);
int mb_cpu_gdb_read_register(CPUState *cpu, GByteArray *buf, int reg);
int mb_cpu_gdb_write_register(CPUState *cpu, uint8_t *buf, int reg);

static inline uint32_t mb_cpu_read_msr(const CPUMBState *env)
{
/* Replicate MSR[C] to MSR[CC]. */
return env->msr | (env->msr_c * (MSR_C | MSR_CC));
}

static inline void mb_cpu_write_msr(CPUMBState *env, uint32_t val)
{
env->msr_c = (val >> 2) & 1;
/*
* Clear both MSR[C] and MSR[CC] from the saved copy.
* MSR_PVR is not writable and is always clear.
*/
env->msr = val & ~(MSR_C | MSR_CC | MSR_PVR);
}

void mb_tcg_init(void);
/* you can call this signal handler from your SIGBUS and SIGSEGV
signal handlers to inform the virtual CPU of exceptions. non zero
Expand Down
4 changes: 2 additions & 2 deletions target/microblaze/gdbstub.c
View file
Expand Up @@ -62,7 +62,7 @@ int mb_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n)
val = env->pc;
break;
case GDB_MSR:
val = env->msr;
val = mb_cpu_read_msr(env);
break;
case GDB_EAR:
val = env->ear;
Expand Down Expand Up @@ -118,7 +118,7 @@ int mb_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
env->pc = tmp;
break;
case GDB_MSR:
env->msr = tmp;
mb_cpu_write_msr(env, tmp);
break;
case GDB_EAR:
env->ear = tmp;
Expand Down
58 changes: 30 additions & 28 deletions target/microblaze/helper.c
View file
Expand Up @@ -112,12 +112,11 @@ void mb_cpu_do_interrupt(CPUState *cs)
{
MicroBlazeCPU *cpu = MICROBLAZE_CPU(cs);
CPUMBState *env = &cpu->env;
uint32_t t;
uint32_t t, msr = mb_cpu_read_msr(env);

/* IMM flag cannot propagate across a branch and into the dslot. */
assert(!((env->iflags & D_FLAG) && (env->iflags & IMM_FLAG)));
assert(!(env->iflags & (DRTI_FLAG | DRTE_FLAG | DRTB_FLAG)));
/* assert(env->msr & (MSR_EE)); Only for HW exceptions. */
env->res_addr = RES_ADDR_NONE;
switch (cs->exception_index) {
case EXCP_HW_EXCP:
Expand All @@ -136,11 +135,12 @@ void mb_cpu_do_interrupt(CPUState *cs)
}

/* Disable the MMU. */
t = (env->msr & (MSR_VM | MSR_UM)) << 1;
env->msr &= ~(MSR_VMS | MSR_UMS | MSR_VM | MSR_UM);
env->msr |= t;
t = (msr & (MSR_VM | MSR_UM)) << 1;
msr &= ~(MSR_VMS | MSR_UMS | MSR_VM | MSR_UM);
msr |= t;
/* Exception in progress. */
env->msr |= MSR_EIP;
msr |= MSR_EIP;
mb_cpu_write_msr(env, msr);

qemu_log_mask(CPU_LOG_INT,
"hw exception at pc=%x ear=%" PRIx64 " "
Expand Down Expand Up @@ -178,11 +178,12 @@ void mb_cpu_do_interrupt(CPUState *cs)
}

/* Disable the MMU. */
t = (env->msr & (MSR_VM | MSR_UM)) << 1;
env->msr &= ~(MSR_VMS | MSR_UMS | MSR_VM | MSR_UM);
env->msr |= t;
t = (msr & (MSR_VM | MSR_UM)) << 1;
msr &= ~(MSR_VMS | MSR_UMS | MSR_VM | MSR_UM);
msr |= t;
/* Exception in progress. */
env->msr |= MSR_EIP;
msr |= MSR_EIP;
mb_cpu_write_msr(env, msr);

qemu_log_mask(CPU_LOG_INT,
"exception at pc=%x ear=%" PRIx64 " iflags=%x\n",
Expand All @@ -193,11 +194,11 @@ void mb_cpu_do_interrupt(CPUState *cs)
break;

case EXCP_IRQ:
assert(!(env->msr & (MSR_EIP | MSR_BIP)));
assert(env->msr & MSR_IE);
assert(!(msr & (MSR_EIP | MSR_BIP)));
assert(msr & MSR_IE);
assert(!(env->iflags & D_FLAG));

t = (env->msr & (MSR_VM | MSR_UM)) << 1;
t = (msr & (MSR_VM | MSR_UM)) << 1;

#if 0
#include "disas/disas.h"
Expand All @@ -212,21 +213,20 @@ void mb_cpu_do_interrupt(CPUState *cs)
&& (!strcmp("netif_rx", sym)
|| !strcmp("process_backlog", sym))) {

qemu_log(
"interrupt at pc=%x msr=%x %x iflags=%x sym=%s\n",
env->pc, env->msr, t, env->iflags,
sym);
qemu_log("interrupt at pc=%x msr=%x %x iflags=%x sym=%s\n",
env->pc, msr, t, env->iflags, sym);

log_cpu_state(cs, 0);
}
}
#endif
qemu_log_mask(CPU_LOG_INT,
"interrupt at pc=%x msr=%x %x iflags=%x\n",
env->pc, env->msr, t, env->iflags);
"interrupt at pc=%x msr=%x %x iflags=%x\n",
env->pc, msr, t, env->iflags);

env->msr &= ~(MSR_VMS | MSR_UMS | MSR_VM | MSR_UM | MSR_IE);
env->msr |= t;
msr &= ~(MSR_VMS | MSR_UMS | MSR_VM | MSR_UM | MSR_IE);
msr |= t;
mb_cpu_write_msr(env, msr);

env->regs[14] = env->pc;
env->pc = cpu->cfg.base_vectors + 0x10;
Expand All @@ -237,20 +237,22 @@ void mb_cpu_do_interrupt(CPUState *cs)
case EXCP_HW_BREAK:
assert(!(env->iflags & IMM_FLAG));
assert(!(env->iflags & D_FLAG));
t = (env->msr & (MSR_VM | MSR_UM)) << 1;
t = (msr & (MSR_VM | MSR_UM)) << 1;
qemu_log_mask(CPU_LOG_INT,
"break at pc=%x msr=%x %x iflags=%x\n",
env->pc, env->msr, t, env->iflags);
env->pc, msr, t, env->iflags);
log_cpu_state_mask(CPU_LOG_INT, cs, 0);
env->msr &= ~(MSR_VMS | MSR_UMS | MSR_VM | MSR_UM);
env->msr |= t;
env->msr |= MSR_BIP;
msr &= ~(MSR_VMS | MSR_UMS | MSR_VM | MSR_UM);
msr |= t;
msr |= MSR_BIP;
if (cs->exception_index == EXCP_HW_BREAK) {
env->regs[16] = env->pc;
env->msr |= MSR_BIP;
msr |= MSR_BIP;
env->pc = cpu->cfg.base_vectors + 0x18;
} else
} else {
env->pc = env->btarget;
}
mb_cpu_write_msr(env, msr);
break;
default:
cpu_abort(cs, "unhandled exception type=%d\n",
Expand Down
91 changes: 29 additions & 62 deletions target/microblaze/translate.c
View file
Expand Up @@ -56,6 +56,7 @@
static TCGv_i32 cpu_R[32];
static TCGv_i32 cpu_pc;
static TCGv_i32 cpu_msr;
static TCGv_i32 cpu_msr_c;
static TCGv_i32 cpu_imm;
static TCGv_i32 cpu_btaken;
static TCGv_i32 cpu_btarget;
Expand Down Expand Up @@ -150,30 +151,6 @@ static void gen_goto_tb(DisasContext *dc, int n, target_ulong dest)
}
}

static void read_carry(DisasContext *dc, TCGv_i32 d)
{
tcg_gen_shri_i32(d, cpu_msr, 31);
}

/*
* write_carry sets the carry bits in MSR based on bit 0 of v.
* v[31:1] are ignored.
*/
static void write_carry(DisasContext *dc, TCGv_i32 v)
{
/* Deposit bit 0 into MSR_C and the alias MSR_CC. */
tcg_gen_deposit_i32(cpu_msr, cpu_msr, v, 2, 1);
tcg_gen_deposit_i32(cpu_msr, cpu_msr, v, 31, 1);
}

static void write_carryi(DisasContext *dc, bool carry)
{
TCGv_i32 t0 = tcg_temp_new_i32();
tcg_gen_movi_i32(t0, carry);
write_carry(dc, t0);
tcg_temp_free_i32(t0);
}

/*
* Returns true if the insn an illegal operation.
* If exceptions are enabled, an exception is raised.
Expand Down Expand Up @@ -243,11 +220,7 @@ static void dec_add(DisasContext *dc)

if (c) {
/* c - Add carry into the result. */
cf = tcg_temp_new_i32();

read_carry(dc, cf);
tcg_gen_add_i32(cpu_R[dc->rd], cpu_R[dc->rd], cf);
tcg_temp_free_i32(cf);
tcg_gen_add_i32(cpu_R[dc->rd], cpu_R[dc->rd], cpu_msr_c);
}
}
return;
Expand All @@ -257,21 +230,15 @@ static void dec_add(DisasContext *dc)
/* Extract carry. */
cf = tcg_temp_new_i32();
if (c) {
read_carry(dc, cf);
tcg_gen_mov_i32(cf, cpu_msr_c);
} else {
tcg_gen_movi_i32(cf, 0);
}

gen_helper_carry(cpu_msr_c, cpu_R[dc->ra], *(dec_alu_op_b(dc)), cf);
if (dc->rd) {
TCGv_i32 ncf = tcg_temp_new_i32();
gen_helper_carry(ncf, cpu_R[dc->ra], *(dec_alu_op_b(dc)), cf);
tcg_gen_add_i32(cpu_R[dc->rd], cpu_R[dc->ra], *(dec_alu_op_b(dc)));
tcg_gen_add_i32(cpu_R[dc->rd], cpu_R[dc->rd], cf);
write_carry(dc, ncf);
tcg_temp_free_i32(ncf);
} else {
gen_helper_carry(cf, cpu_R[dc->ra], *(dec_alu_op_b(dc)), cf);
write_carry(dc, cf);
}
tcg_temp_free_i32(cf);
}
Expand Down Expand Up @@ -309,11 +276,7 @@ static void dec_sub(DisasContext *dc)

if (c) {
/* c - Add carry into the result. */
cf = tcg_temp_new_i32();

read_carry(dc, cf);
tcg_gen_add_i32(cpu_R[dc->rd], cpu_R[dc->rd], cf);
tcg_temp_free_i32(cf);
tcg_gen_add_i32(cpu_R[dc->rd], cpu_R[dc->rd], cpu_msr_c);
}
}
return;
Expand All @@ -324,24 +287,18 @@ static void dec_sub(DisasContext *dc)
cf = tcg_temp_new_i32();
na = tcg_temp_new_i32();
if (c) {
read_carry(dc, cf);
tcg_gen_mov_i32(cf, cpu_msr_c);
} else {
tcg_gen_movi_i32(cf, 1);
}

/* d = b + ~a + c. carry defaults to 1. */
tcg_gen_not_i32(na, cpu_R[dc->ra]);

gen_helper_carry(cpu_msr_c, na, *(dec_alu_op_b(dc)), cf);
if (dc->rd) {
TCGv_i32 ncf = tcg_temp_new_i32();
gen_helper_carry(ncf, na, *(dec_alu_op_b(dc)), cf);
tcg_gen_add_i32(cpu_R[dc->rd], na, *(dec_alu_op_b(dc)));
tcg_gen_add_i32(cpu_R[dc->rd], cpu_R[dc->rd], cf);
write_carry(dc, ncf);
tcg_temp_free_i32(ncf);
} else {
gen_helper_carry(cf, na, *(dec_alu_op_b(dc)), cf);
write_carry(dc, cf);
}
tcg_temp_free_i32(cf);
tcg_temp_free_i32(na);
Expand Down Expand Up @@ -429,16 +386,26 @@ static void dec_xor(DisasContext *dc)
tcg_gen_xor_i32(cpu_R[dc->rd], cpu_R[dc->ra], *(dec_alu_op_b(dc)));
}

static inline void msr_read(DisasContext *dc, TCGv_i32 d)
static void msr_read(DisasContext *dc, TCGv_i32 d)
{
tcg_gen_mov_i32(d, cpu_msr);
TCGv_i32 t;

/* Replicate the cpu_msr_c boolean into the proper bit and the copy. */
t = tcg_temp_new_i32();
tcg_gen_muli_i32(t, cpu_msr_c, MSR_C | MSR_CC);
tcg_gen_or_i32(d, cpu_msr, t);
tcg_temp_free_i32(t);
}

static inline void msr_write(DisasContext *dc, TCGv_i32 v)
static void msr_write(DisasContext *dc, TCGv_i32 v)
{
dc->cpustate_changed = 1;
/* PVR bit is not writable, and is never set. */
tcg_gen_andi_i32(cpu_msr, v, ~MSR_PVR);

/* Install MSR_C. */
tcg_gen_extract_i32(cpu_msr_c, v, 2, 1);

/* Clear MSR_C and MSR_CC; MSR_PVR is not writable, and is always clear. */
tcg_gen_andi_i32(cpu_msr, v, ~(MSR_C | MSR_CC | MSR_PVR));
}

static void dec_msr(DisasContext *dc)
Expand Down Expand Up @@ -778,8 +745,8 @@ static void dec_bit(DisasContext *dc)
t0 = tcg_temp_new_i32();

LOG_DIS("src r%d r%d\n", dc->rd, dc->ra);
tcg_gen_andi_i32(t0, cpu_msr, MSR_CC);
write_carry(dc, cpu_R[dc->ra]);
tcg_gen_shli_i32(t0, cpu_msr_c, 31);
tcg_gen_andi_i32(cpu_msr_c, cpu_R[dc->ra], 1);
if (dc->rd) {
tcg_gen_shri_i32(cpu_R[dc->rd], cpu_R[dc->ra], 1);
tcg_gen_or_i32(cpu_R[dc->rd], cpu_R[dc->rd], t0);
Expand All @@ -792,8 +759,7 @@ static void dec_bit(DisasContext *dc)
/* srl. */
LOG_DIS("srl r%d r%d\n", dc->rd, dc->ra);

/* Update carry. Note that write carry only looks at the LSB. */
write_carry(dc, cpu_R[dc->ra]);
tcg_gen_andi_i32(cpu_msr_c, cpu_R[dc->ra], 1);
if (dc->rd) {
if (op == 0x41)
tcg_gen_shri_i32(cpu_R[dc->rd], cpu_R[dc->ra], 1);
Expand Down Expand Up @@ -1042,7 +1008,7 @@ static void dec_load(DisasContext *dc)

if (ex) { /* lwx */
/* no support for AXI exclusive so always clear C */
write_carryi(dc, 0);
tcg_gen_movi_i32(cpu_msr_c, 0);
}

tcg_temp_free(addr);
Expand Down Expand Up @@ -1093,7 +1059,7 @@ static void dec_store(DisasContext *dc)
/* swx does not throw unaligned access errors, so force alignment */
tcg_gen_andi_tl(addr, addr, ~3);

write_carryi(dc, 1);
tcg_gen_movi_i32(cpu_msr_c, 1);
swx_skip = gen_new_label();
tcg_gen_brcond_tl(TCG_COND_NE, cpu_res_addr, addr, swx_skip);

Expand All @@ -1108,7 +1074,7 @@ static void dec_store(DisasContext *dc)
mop);

tcg_gen_brcond_i32(TCG_COND_NE, cpu_res_val, tval, swx_skip);
write_carryi(dc, 0);
tcg_gen_movi_i32(cpu_msr_c, 0);
tcg_temp_free_i32(tval);
}

Expand Down Expand Up @@ -1851,6 +1817,7 @@ void mb_tcg_init(void)

SP(pc),
SP(msr),
SP(msr_c),
SP(imm),
SP(iflags),
SP(btaken),
Expand Down

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