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Clean up and refactor ReplaceBack optimization to allow loops #365

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Merged
totalspectrum merged 1 commit into from
Apr 5, 2023
Merged

Clean up and refactor ReplaceBack optimization to allow loops #365

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168 changes: 88 additions & 80 deletions backends/asm/optimize_ir.c
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,50 @@ int gl_fcache_size = -1;
// helper functions
//


// a kingdom for a std::vector....
struct dependency {
struct dependency *link;
Operand *reg;
};

static void DeleteDependencyList(struct dependency **list) {
for (struct dependency *tmp=*list; tmp;) {
struct dependency *tmp2 = tmp->link;
free(tmp);
tmp=tmp2;
}
*list = NULL;
}

static void PrependDependency(struct dependency **list,Operand *reg) {
struct dependency *tmp = (struct dependency *)malloc(sizeof(struct dependency));
tmp->link = *list;
tmp->reg = reg;
*list = tmp;
}

static bool CheckDependency(struct dependency **list, Operand *reg) {
for (struct dependency *tmp=*list; tmp; tmp=tmp->link) {
if (tmp->reg == reg) return true;
}
return false;
}

static void DeleteDependencies(struct dependency **list,Operand *reg) {
struct dependency **prevlink = list;
for (struct dependency *tmp=*list; tmp;) {
struct dependency *next = tmp->link;
if (tmp->reg == reg) {
*prevlink = next;
free(tmp);
} else {
prevlink = &tmp->link;
}
tmp=next;
}
}

/* IR instructions that have no effect on the generated code */
bool IsDummy(IR *op)
{
Expand Down Expand Up @@ -1210,64 +1254,84 @@ IsDeadAfter(IR *instr, Operand *op)
return doIsDeadAfter(instr, op, 1, stack);
}

static bool
static IR*
SafeToReplaceBack(IR *instr, Operand *orig, Operand *replace)
{
IR *ir;
IR *last_ir = NULL;
int usecount = 0;

if (SrcOnlyHwReg(replace) || !IsRegister(replace->kind))
return false;
return NULL;
if (replace->kind == REG_SUBREG || (orig && orig->kind == REG_SUBREG) ) {
return false;
return NULL;
}
for (ir = instr; ir; ir = ir->prev) {

struct dependency *up_labels = NULL; // Outstanding loop label list

for (IR *ir = instr; ir; ir = ir->prev) {
last_ir = ir;
if (IsDummy(ir)) {
continue;
}
if (ir->opc == OPC_LABEL) {
if (ir->flags & FLAG_LABEL_NOJUMP) {
continue;
} else if (CheckDependency(&up_labels,ir->dst)) {
DeleteDependencies(&up_labels,ir->dst);
continue;
}
return false;
goto fail;
}
if (ir->opc == OPC_LIVE) {
return false;
goto fail;
}
if (IsJump(ir)) {
return false;
if (!(curfunc->optimize_flags & OPT_EXPERIMENTAL) || IsHwReg(replace)) {
// Safety fail
goto fail;
} else if (IsForwardJump(ir)) {
// Could probably also handle down labels in separate list...
goto fail;
} else {
PrependDependency(&up_labels,JumpDest(ir));
}
}
if (IsCallThatUsesReg(ir,orig) || IsCallThatUsesReg(ir,replace)) {
return false;
goto fail;
}
if (InstrModifies(ir, orig) && !InstrReadsDst(ir)) {
if (InstrIsVolatile(ir)) return false;
// Note: InstrModifies does some weird stuff with subregisters, so check like this instead
if (ir->dst == orig && InstrSetsDst(ir) && !InstrReadsDst(ir)) {
if (InstrIsVolatile(ir)) goto fail;
if (IsHwReg(replace) && ir->src && IsHwReg(ir->src) && ir->src != replace)
{
return false;
goto fail;
}
if (usecount > 0 && IsHwReg(replace) && ir->src != replace) {
return false;
goto fail;
}
// this was perhaps overly cautious, but I can remember a lot of headaches
// around optimization, so we may need to revert to it
//return ir->cond == COND_TRUE;
if (ir->cond == COND_TRUE) return true;
if (ir->cond == COND_TRUE && !up_labels) return ir;
}
if (InstrUses(ir, replace) || ir->dst == replace) {
return false;
goto fail;
}
if ( (InstrUses(ir, orig) || InstrModifies(ir, orig)) && IsHwReg(replace)) {
if (IsHwReg(replace) && (InstrUses(ir, orig) || InstrModifies(ir, orig))) {
if (usecount > 0) {
return false;
goto fail;
}
usecount++;
}
}
// we've reached the start
// is orig dead here? if so we can replace it
// args are live, and so are globals
return IsLocal(orig);
if (!up_labels && IsLocal(orig)) return last_ir;
// Fall into fail case
fail:
DeleteDependencyList(&up_labels);
return NULL;
}

//
Expand Down Expand Up @@ -1486,25 +1550,13 @@ SafeToReplaceForward(IR *first_ir, Operand *orig, Operand *replace, IRCond sette


static void
ReplaceBack(IR *instr, Operand *orig, Operand *replace)
ReplaceBack(IR *instr, Operand *orig, Operand *replace, IR *stop_ir)
{
IR *ir;
for (ir = instr; ir; ir = ir->prev) {
if (ir->opc == OPC_LABEL) {
if (ir->flags & FLAG_LABEL_NOJUMP) {
continue;
}
break;
}
if (ir->dst == orig) {
ir->dst = replace;
if (InstrSetsDst(ir) && !InstrReadsDst(ir) && ir->cond == COND_TRUE) {
break;
}
}
if (ir->src == orig) {
ir->src = replace;
}
if (ir->dst == orig) ir->dst = replace;
if (ir == stop_ir) break;
if (ir->src == orig) ir->src = replace;
}
}

Expand Down Expand Up @@ -2317,8 +2369,8 @@ OptimizeMoves(IRList *irl)
if (ir->src == ir->dst && !InstrSetsAnyFlags(ir)) {
DeleteIR(irl, ir);
change = 1;
} else if (!InstrSetsAnyFlags(ir) && ir->cond == COND_TRUE && IsDeadAfter(ir, ir->src) && SafeToReplaceBack(ir->prev, ir->src, ir->dst)) {
ReplaceBack(ir->prev, ir->src, ir->dst);
} else if (!InstrSetsAnyFlags(ir) && ir->cond == COND_TRUE && IsDeadAfter(ir, ir->src) && (stop_ir = SafeToReplaceBack(ir->prev, ir->src, ir->dst))) {
ReplaceBack(ir->prev, ir->src, ir->dst, stop_ir);
DeleteIR(irl, ir);
change = 1;
}
Expand Down Expand Up @@ -4610,50 +4662,6 @@ struct reorder_block {
IR *top,*bottom;
};


// a kingdom for a std::vector....
struct dependency {
struct dependency *link;
Operand *reg;
};

static void DeleteDependencyList(struct dependency **list) {
for (struct dependency *tmp=*list; tmp;) {
struct dependency *tmp2 = tmp->link;
free(tmp);
tmp=tmp2;
}
*list = NULL;
}

static void PrependDependency(struct dependency **list,Operand *reg) {
struct dependency *tmp = (struct dependency *)malloc(sizeof(struct dependency));
tmp->link = *list;
tmp->reg = reg;
*list = tmp;
}

static bool CheckDependency(struct dependency **list, Operand *reg) {
for (struct dependency *tmp=*list; tmp; tmp=tmp->link) {
if (tmp->reg == reg) return true;
}
return false;
}

static void DeleteDependencies(struct dependency **list,Operand *reg) {
struct dependency **prevlink = list;
for (struct dependency *tmp=*list; tmp;) {
struct dependency *next = tmp->link;
if (tmp->reg == reg) {
*prevlink = next;
free(tmp);
} else {
prevlink = &tmp->link;
}
tmp=next;
}
}

static struct reorder_block
FindBlockForReorderingDownward(IR *after) {
IR *bottom = after;
Expand Down