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Optimise out redundant uOPs, where the output register is never read.

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This commit is contained in:
SarahW 2019-02-10 12:32:25 +00:00
commit 3f2d9ecf87
4 changed files with 200 additions and 57 deletions
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64
src/codegen_reg.h
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@ -272,7 +272,36 @@ static inline int ireg_seg_limit_high(x86seg *seg)
}
extern uint8_t reg_last_version[IREG_COUNT];
extern uint8_t reg_version_refcount[IREG_COUNT][256];
/*This version of the register must be calculated, regardless of whether it is
apparently required or not. Do not optimise out.*/
#define REG_FLAGS_REQUIRED (1 << 0)
/*This register and the parent uOP have been optimised out.*/
#define REG_FLAGS_DEAD (1 << 1)
typedef struct
{
/*Refcount of pending reads on this register version*/
uint8_t refcount;
/*Flags*/
uint8_t flags;
/*uOP that generated this register version*/
uint16_t parent_uop;
/*Pointer to next register version in dead register list*/
uint16_t next;
} reg_version_t;
extern reg_version_t reg_version[IREG_COUNT][256];
/*Head of dead register list; a list of register versions that are not used and
can be optimised out*/
extern uint16_t reg_dead_list;
static inline void add_to_dead_list(reg_version_t *regv, int reg, int version)
{
regv->next = reg_dead_list;
reg_dead_list = version | (reg << 8);
}
typedef struct
{
@ -289,37 +318,50 @@ typedef uint16_t ir_host_reg_t;
static inline ir_reg_t codegen_reg_read(int reg)
{
ir_reg_t ireg;
reg_version_t *version;
if (IREG_GET_REG(reg) == IREG_INVALID)
fatal("codegen_reg_read - IREG_INVALID\n");
ireg.reg = reg;
ireg.version = reg_last_version[IREG_GET_REG(reg)];
reg_version_refcount[IREG_GET_REG(ireg.reg)][ireg.version]++;
if (!reg_version_refcount[IREG_GET_REG(ireg.reg)][ireg.version])
version = &reg_version[IREG_GET_REG(ireg.reg)][ireg.version];
version->flags = 0;
version->refcount++;
if (!version->refcount)
fatal("codegen_reg_read - refcount overflow\n");
else if (reg_version_refcount[IREG_GET_REG(ireg.reg)][ireg.version] > REG_VERSION_MAX)
else if (version->refcount > REG_VERSION_MAX)
CPU_BLOCK_END();
// pclog("codegen_reg_read: %i %i %i\n", reg & IREG_REG_MASK, ireg.version, reg_version_refcount[IREG_GET_REG(ireg.reg)][ireg.version]);
return ireg;
}
static inline ir_reg_t codegen_reg_write(int reg)
static inline ir_reg_t codegen_reg_write(int reg, int uop_nr)
{
ir_reg_t ireg;
int last_version = reg_last_version[IREG_GET_REG(reg)];
reg_version_t *version;
if (IREG_GET_REG(reg) == IREG_INVALID)
fatal("codegen_reg_write - IREG_INVALID\n");
ireg.reg = reg;
ireg.version = reg_last_version[IREG_GET_REG(reg)] + 1;
ireg.version = last_version + 1;
if (IREG_GET_REG(reg) > IREG_EBX && last_version && !reg_version[IREG_GET_REG(reg)][last_version].refcount &&
!(reg_version[IREG_GET_REG(reg)][last_version].flags & REG_FLAGS_REQUIRED))
add_to_dead_list(&reg_version[IREG_GET_REG(reg)][last_version], IREG_GET_REG(reg), last_version);
reg_last_version[IREG_GET_REG(reg)]++;
if (!reg_last_version[IREG_GET_REG(reg)])
fatal("codegen_reg_write - version overflow\n");
else if (reg_last_version[IREG_GET_REG(reg)] > REG_VERSION_MAX)
CPU_BLOCK_END();
reg_version_refcount[IREG_GET_REG(reg)][ireg.version] = 0;
version = &reg_version[IREG_GET_REG(reg)][ireg.version];
version->refcount = 0;
version->flags = 0;
version->parent_uop = uop_nr;
// pclog("codegen_reg_write: %i\n", reg & IREG_REG_MASK);
return ireg;
}
@ -337,4 +379,6 @@ void codegen_reg_alloc_register(ir_reg_t dest_reg_a, ir_reg_t src_reg_a, ir_reg_
ir_host_reg_t codegen_reg_alloc_read_reg(codeblock_t *block, ir_reg_t ir_reg, int *host_reg_idx);
ir_host_reg_t codegen_reg_alloc_write_reg(codeblock_t *block, ir_reg_t ir_reg);
void codegen_reg_mark_as_required();
void codegen_reg_process_dead_list(struct ir_data_t *ir);
#endif