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qemu/hw/misc/milkymist-pfpu.c
Radim Krčmář c6dc3dd72b milkymist-pfpu: fix GCC 5.0.0 aggressive-loop-optimizations warning 
man gcc:
  Warn if in a loop with constant number of iterations the compiler
  detects undefined behavior in some statement during one or more of
  the iterations.

Milkymist pfpu has no jump instructions, so checking for MICROCODE_WORDS
instructions should have kept us in bounds of s->microcode, but i++
allowed one loop too many,

  hw/misc/milkymist-pfpu.c: In function ‘pfpu_write’:
  hw/misc/milkymist-pfpu.c:365:20: error: loop exit may only be reached after undefined behavior [-Werror=aggressive-loop-optimizations]
                   if (i++ >= MICROCODE_WORDS) {
                      ^
  hw/misc/milkymist-pfpu.c:167:14: note: possible undefined statement is here
       uint32_t insn = s->microcode[pc];
                ^

The code can still access out of bounds, because it presumes that PC register
always begins at 0, and we allow writing to it.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Acked-by: Michael Walle <michael@walle.cc>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
2015-03-10 08:15:34 +03:00

549 lines
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/*
* QEMU model of the Milkymist programmable FPU.
*
* Copyright (c) 2010 Michael Walle <michael@walle.cc>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
*
* Specification available at:
* http://www.milkymist.org/socdoc/pfpu.pdf
*
*/
#include "hw/hw.h"
#include "hw/sysbus.h"
#include "trace.h"
#include "qemu/log.h"
#include "qemu/error-report.h"
#include <math.h>
/* #define TRACE_EXEC */
#ifdef TRACE_EXEC
# define D_EXEC(x) x
#else
# define D_EXEC(x)
#endif
enum {
R_CTL = 0,
R_MESHBASE,
R_HMESHLAST,
R_VMESHLAST,
R_CODEPAGE,
R_VERTICES,
R_COLLISIONS,
R_STRAYWRITES,
R_LASTDMA,
R_PC,
R_DREGBASE,
R_CODEBASE,
R_MAX
};
enum {
CTL_START_BUSY = (1<<0),
};
enum {
OP_NOP = 0,
OP_FADD,
OP_FSUB,
OP_FMUL,
OP_FABS,
OP_F2I,
OP_I2F,
OP_VECTOUT,
OP_SIN,
OP_COS,
OP_ABOVE,
OP_EQUAL,
OP_COPY,
OP_IF,
OP_TSIGN,
OP_QUAKE,
};
enum {
GPR_X = 0,
GPR_Y = 1,
GPR_FLAGS = 2,
};
enum {
LATENCY_FADD = 5,
LATENCY_FSUB = 5,
LATENCY_FMUL = 7,
LATENCY_FABS = 2,
LATENCY_F2I = 2,
LATENCY_I2F = 3,
LATENCY_VECTOUT = 0,
LATENCY_SIN = 4,
LATENCY_COS = 4,
LATENCY_ABOVE = 2,
LATENCY_EQUAL = 2,
LATENCY_COPY = 2,
LATENCY_IF = 2,
LATENCY_TSIGN = 2,
LATENCY_QUAKE = 2,
MAX_LATENCY = 7
};
#define GPR_BEGIN 0x100
#define GPR_END 0x17f
#define MICROCODE_BEGIN 0x200
#define MICROCODE_END 0x3ff
#define MICROCODE_WORDS 2048
#define REINTERPRET_CAST(type, val) (*((type *)&(val)))
#ifdef TRACE_EXEC
static const char *opcode_to_str[] = {
"NOP", "FADD", "FSUB", "FMUL", "FABS", "F2I", "I2F", "VECTOUT",
"SIN", "COS", "ABOVE", "EQUAL", "COPY", "IF", "TSIGN", "QUAKE",
};
#endif
#define TYPE_MILKYMIST_PFPU "milkymist-pfpu"
#define MILKYMIST_PFPU(obj) \
OBJECT_CHECK(MilkymistPFPUState, (obj), TYPE_MILKYMIST_PFPU)
struct MilkymistPFPUState {
SysBusDevice parent_obj;
MemoryRegion regs_region;
CharDriverState *chr;
qemu_irq irq;
uint32_t regs[R_MAX];
uint32_t gp_regs[128];
uint32_t microcode[MICROCODE_WORDS];
int output_queue_pos;
uint32_t output_queue[MAX_LATENCY];
};
typedef struct MilkymistPFPUState MilkymistPFPUState;
static inline hwaddr
get_dma_address(uint32_t base, uint32_t x, uint32_t y)
{
return base + 8 * (128 * y + x);
}
static inline void
output_queue_insert(MilkymistPFPUState *s, uint32_t val, int pos)
{
s->output_queue[(s->output_queue_pos + pos) % MAX_LATENCY] = val;
}
static inline uint32_t
output_queue_remove(MilkymistPFPUState *s)
{
return s->output_queue[s->output_queue_pos];
}
static inline void
output_queue_advance(MilkymistPFPUState *s)
{
s->output_queue[s->output_queue_pos] = 0;
s->output_queue_pos = (s->output_queue_pos + 1) % MAX_LATENCY;
}
static int pfpu_decode_insn(MilkymistPFPUState *s)
{
uint32_t pc = s->regs[R_PC];
uint32_t insn = s->microcode[pc];
uint32_t reg_a = (insn >> 18) & 0x7f;
uint32_t reg_b = (insn >> 11) & 0x7f;
uint32_t op = (insn >> 7) & 0xf;
uint32_t reg_d = insn & 0x7f;
uint32_t r = 0;
int latency = 0;
switch (op) {
case OP_NOP:
break;
case OP_FADD:
{
float a = REINTERPRET_CAST(float, s->gp_regs[reg_a]);
float b = REINTERPRET_CAST(float, s->gp_regs[reg_b]);
float t = a + b;
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_FADD;
D_EXEC(qemu_log("ADD a=%f b=%f t=%f, r=%08x\n", a, b, t, r));
} break;
case OP_FSUB:
{
float a = REINTERPRET_CAST(float, s->gp_regs[reg_a]);
float b = REINTERPRET_CAST(float, s->gp_regs[reg_b]);
float t = a - b;
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_FSUB;
D_EXEC(qemu_log("SUB a=%f b=%f t=%f, r=%08x\n", a, b, t, r));
} break;
case OP_FMUL:
{
float a = REINTERPRET_CAST(float, s->gp_regs[reg_a]);
float b = REINTERPRET_CAST(float, s->gp_regs[reg_b]);
float t = a * b;
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_FMUL;
D_EXEC(qemu_log("MUL a=%f b=%f t=%f, r=%08x\n", a, b, t, r));
} break;
case OP_FABS:
{
float a = REINTERPRET_CAST(float, s->gp_regs[reg_a]);
float t = fabsf(a);
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_FABS;
D_EXEC(qemu_log("ABS a=%f t=%f, r=%08x\n", a, t, r));
} break;
case OP_F2I:
{
float a = REINTERPRET_CAST(float, s->gp_regs[reg_a]);
int32_t t = a;
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_F2I;
D_EXEC(qemu_log("F2I a=%f t=%d, r=%08x\n", a, t, r));
} break;
case OP_I2F:
{
int32_t a = REINTERPRET_CAST(int32_t, s->gp_regs[reg_a]);
float t = a;
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_I2F;
D_EXEC(qemu_log("I2F a=%08x t=%f, r=%08x\n", a, t, r));
} break;
case OP_VECTOUT:
{
uint32_t a = cpu_to_be32(s->gp_regs[reg_a]);
uint32_t b = cpu_to_be32(s->gp_regs[reg_b]);
hwaddr dma_ptr =
get_dma_address(s->regs[R_MESHBASE],
s->gp_regs[GPR_X], s->gp_regs[GPR_Y]);
cpu_physical_memory_write(dma_ptr, &a, 4);
cpu_physical_memory_write(dma_ptr + 4, &b, 4);
s->regs[R_LASTDMA] = dma_ptr + 4;
D_EXEC(qemu_log("VECTOUT a=%08x b=%08x dma=%08x\n", a, b, dma_ptr));
trace_milkymist_pfpu_vectout(a, b, dma_ptr);
} break;
case OP_SIN:
{
int32_t a = REINTERPRET_CAST(int32_t, s->gp_regs[reg_a]);
float t = sinf(a * (1.0f / (M_PI * 4096.0f)));
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_SIN;
D_EXEC(qemu_log("SIN a=%d t=%f, r=%08x\n", a, t, r));
} break;
case OP_COS:
{
int32_t a = REINTERPRET_CAST(int32_t, s->gp_regs[reg_a]);
float t = cosf(a * (1.0f / (M_PI * 4096.0f)));
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_COS;
D_EXEC(qemu_log("COS a=%d t=%f, r=%08x\n", a, t, r));
} break;
case OP_ABOVE:
{
float a = REINTERPRET_CAST(float, s->gp_regs[reg_a]);
float b = REINTERPRET_CAST(float, s->gp_regs[reg_b]);
float t = (a > b) ? 1.0f : 0.0f;
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_ABOVE;
D_EXEC(qemu_log("ABOVE a=%f b=%f t=%f, r=%08x\n", a, b, t, r));
} break;
case OP_EQUAL:
{
float a = REINTERPRET_CAST(float, s->gp_regs[reg_a]);
float b = REINTERPRET_CAST(float, s->gp_regs[reg_b]);
float t = (a == b) ? 1.0f : 0.0f;
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_EQUAL;
D_EXEC(qemu_log("EQUAL a=%f b=%f t=%f, r=%08x\n", a, b, t, r));
} break;
case OP_COPY:
{
r = s->gp_regs[reg_a];
latency = LATENCY_COPY;
D_EXEC(qemu_log("COPY"));
} break;
case OP_IF:
{
float a = REINTERPRET_CAST(float, s->gp_regs[reg_a]);
float b = REINTERPRET_CAST(float, s->gp_regs[reg_b]);
uint32_t f = s->gp_regs[GPR_FLAGS];
float t = (f != 0) ? a : b;
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_IF;
D_EXEC(qemu_log("IF f=%u a=%f b=%f t=%f, r=%08x\n", f, a, b, t, r));
} break;
case OP_TSIGN:
{
float a = REINTERPRET_CAST(float, s->gp_regs[reg_a]);
float b = REINTERPRET_CAST(float, s->gp_regs[reg_b]);
float t = (b < 0) ? -a : a;
r = REINTERPRET_CAST(uint32_t, t);
latency = LATENCY_TSIGN;
D_EXEC(qemu_log("TSIGN a=%f b=%f t=%f, r=%08x\n", a, b, t, r));
} break;
case OP_QUAKE:
{
uint32_t a = s->gp_regs[reg_a];
r = 0x5f3759df - (a >> 1);
latency = LATENCY_QUAKE;
D_EXEC(qemu_log("QUAKE a=%d r=%08x\n", a, r));
} break;
default:
error_report("milkymist_pfpu: unknown opcode %d", op);
break;
}
if (!reg_d) {
D_EXEC(qemu_log("%04d %8s R%03d, R%03d <L=%d, E=%04d>\n",
s->regs[R_PC], opcode_to_str[op], reg_a, reg_b, latency,
s->regs[R_PC] + latency));
} else {
D_EXEC(qemu_log("%04d %8s R%03d, R%03d <L=%d, E=%04d> -> R%03d\n",
s->regs[R_PC], opcode_to_str[op], reg_a, reg_b, latency,
s->regs[R_PC] + latency, reg_d));
}
if (op == OP_VECTOUT) {
return 0;
}
/* store output for this cycle */
if (reg_d) {
uint32_t val = output_queue_remove(s);
D_EXEC(qemu_log("R%03d <- 0x%08x\n", reg_d, val));
s->gp_regs[reg_d] = val;
}
output_queue_advance(s);
/* store op output */
if (op != OP_NOP) {
output_queue_insert(s, r, latency-1);
}
/* advance PC */
s->regs[R_PC]++;
return 1;
};
static void pfpu_start(MilkymistPFPUState *s)
{
int x, y;
int i;
for (y = 0; y <= s->regs[R_VMESHLAST]; y++) {
for (x = 0; x <= s->regs[R_HMESHLAST]; x++) {
D_EXEC(qemu_log("\nprocessing x=%d y=%d\n", x, y));
/* set current position */
s->gp_regs[GPR_X] = x;
s->gp_regs[GPR_Y] = y;
/* run microcode on this position */
i = 0;
while (pfpu_decode_insn(s)) {
/* decode at most MICROCODE_WORDS instructions */
if (++i >= MICROCODE_WORDS) {
error_report("milkymist_pfpu: too many instructions "
"executed in microcode. No VECTOUT?");
break;
}
}
/* reset pc for next run */
s->regs[R_PC] = 0;
}
}
s->regs[R_VERTICES] = x * y;
trace_milkymist_pfpu_pulse_irq();
qemu_irq_pulse(s->irq);
}
static inline int get_microcode_address(MilkymistPFPUState *s, uint32_t addr)
{
return (512 * s->regs[R_CODEPAGE]) + addr - MICROCODE_BEGIN;
}
static uint64_t pfpu_read(void *opaque, hwaddr addr,
unsigned size)
{
MilkymistPFPUState *s = opaque;
uint32_t r = 0;
addr >>= 2;
switch (addr) {
case R_CTL:
case R_MESHBASE:
case R_HMESHLAST:
case R_VMESHLAST:
case R_CODEPAGE:
case R_VERTICES:
case R_COLLISIONS:
case R_STRAYWRITES:
case R_LASTDMA:
case R_PC:
case R_DREGBASE:
case R_CODEBASE:
r = s->regs[addr];
break;
case GPR_BEGIN ... GPR_END:
r = s->gp_regs[addr - GPR_BEGIN];
break;
case MICROCODE_BEGIN ... MICROCODE_END:
r = s->microcode[get_microcode_address(s, addr)];
break;
default:
error_report("milkymist_pfpu: read access to unknown register 0x"
TARGET_FMT_plx, addr << 2);
break;
}
trace_milkymist_pfpu_memory_read(addr << 2, r);
return r;
}
static void pfpu_write(void *opaque, hwaddr addr, uint64_t value,
unsigned size)
{
MilkymistPFPUState *s = opaque;
trace_milkymist_pfpu_memory_write(addr, value);
addr >>= 2;
switch (addr) {
case R_CTL:
if (value & CTL_START_BUSY) {
pfpu_start(s);
}
break;
case R_MESHBASE:
case R_HMESHLAST:
case R_VMESHLAST:
case R_CODEPAGE:
case R_VERTICES:
case R_COLLISIONS:
case R_STRAYWRITES:
case R_LASTDMA:
case R_PC:
case R_DREGBASE:
case R_CODEBASE:
s->regs[addr] = value;
break;
case GPR_BEGIN ... GPR_END:
s->gp_regs[addr - GPR_BEGIN] = value;
break;
case MICROCODE_BEGIN ... MICROCODE_END:
s->microcode[get_microcode_address(s, addr)] = value;
break;
default:
error_report("milkymist_pfpu: write access to unknown register 0x"
TARGET_FMT_plx, addr << 2);
break;
}
}
static const MemoryRegionOps pfpu_mmio_ops = {
.read = pfpu_read,
.write = pfpu_write,
.valid = {
.min_access_size = 4,
.max_access_size = 4,
},
.endianness = DEVICE_NATIVE_ENDIAN,
};
static void milkymist_pfpu_reset(DeviceState *d)
{
MilkymistPFPUState *s = MILKYMIST_PFPU(d);
int i;
for (i = 0; i < R_MAX; i++) {
s->regs[i] = 0;
}
for (i = 0; i < 128; i++) {
s->gp_regs[i] = 0;
}
for (i = 0; i < MICROCODE_WORDS; i++) {
s->microcode[i] = 0;
}
s->output_queue_pos = 0;
for (i = 0; i < MAX_LATENCY; i++) {
s->output_queue[i] = 0;
}
}
static int milkymist_pfpu_init(SysBusDevice *dev)
{
MilkymistPFPUState *s = MILKYMIST_PFPU(dev);
sysbus_init_irq(dev, &s->irq);
memory_region_init_io(&s->regs_region, OBJECT(dev), &pfpu_mmio_ops, s,
"milkymist-pfpu", MICROCODE_END * 4);
sysbus_init_mmio(dev, &s->regs_region);
return 0;
}
static const VMStateDescription vmstate_milkymist_pfpu = {
.name = "milkymist-pfpu",
.version_id = 1,
.minimum_version_id = 1,
.fields = (VMStateField[]) {
VMSTATE_UINT32_ARRAY(regs, MilkymistPFPUState, R_MAX),
VMSTATE_UINT32_ARRAY(gp_regs, MilkymistPFPUState, 128),
VMSTATE_UINT32_ARRAY(microcode, MilkymistPFPUState, MICROCODE_WORDS),
VMSTATE_INT32(output_queue_pos, MilkymistPFPUState),
VMSTATE_UINT32_ARRAY(output_queue, MilkymistPFPUState, MAX_LATENCY),
VMSTATE_END_OF_LIST()
}
};
static void milkymist_pfpu_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
k->init = milkymist_pfpu_init;
dc->reset = milkymist_pfpu_reset;
dc->vmsd = &vmstate_milkymist_pfpu;
}
static const TypeInfo milkymist_pfpu_info = {
.name = TYPE_MILKYMIST_PFPU,
.parent = TYPE_SYS_BUS_DEVICE,
.instance_size = sizeof(MilkymistPFPUState),
.class_init = milkymist_pfpu_class_init,
};
static void milkymist_pfpu_register_types(void)
{
type_register_static(&milkymist_pfpu_info);
}
type_init(milkymist_pfpu_register_types)
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