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gm107/ir: prevent WaW hazards in instruction scheduling

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Previously, findFirstUse() only considered reads "uses". This fixes that
by making it check both an instruction's sources and definitions. It
also shortens both findFistUse() and findFirstDef() along the way.

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
This commit is contained in:
Rhys Perry 2018-05-19 22:03:39 +01:00 • committed by Ilia Mirkin
parent a29bc043ae
commit 57e721a456
1 changed files with 56 additions and 53 deletions
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109
src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gm107.cpp
View file

@ -3618,6 +3618,7 @@ private:
bool insertBarriers(BasicBlock *);
bool doesInsnWriteTo(const Instruction *insn, const Value *val) const;
Instruction *findFirstUse(const Instruction *) const;
Instruction *findFirstDef(const Instruction *) const;
@ -3948,8 +3949,48 @@ SchedDataCalculatorGM107::needWrDepBar(const Instruction *insn) const
return false;
}
// Find the next instruction inside the same basic block which uses the output
// of the given instruction in order to avoid RaW hazards.
// Helper function for findFirstUse() and findFirstDef()
bool
SchedDataCalculatorGM107::doesInsnWriteTo(const Instruction *insn,
const Value *val) const
{
if (val->reg.file != FILE_GPR &&
val->reg.file != FILE_PREDICATE &&
val->reg.file != FILE_FLAGS)
return false;
for (int d = 0; insn->defExists(d); ++d) {
const Value* def = insn->getDef(d);
int minGPR = def->reg.data.id;
int maxGPR = minGPR + def->reg.size / 4 - 1;
if (def->reg.file != val->reg.file)
continue;
if (def->reg.file == FILE_GPR) {
if (val->reg.data.id + val->reg.size / 4 - 1 < minGPR ||
val->reg.data.id > maxGPR)
continue;
return true;
} else
if (def->reg.file == FILE_PREDICATE) {
if (val->reg.data.id != minGPR)
continue;
return true;
} else
if (def->reg.file == FILE_FLAGS) {
if (val->reg.data.id != minGPR)
continue;
return true;
}
}
return false;
}
// Find the next instruction inside the same basic block which uses (reads or
// writes from) the output of the given instruction in order to avoid RaW and
// WaW hazards.
Instruction *
SchedDataCalculatorGM107::findFirstUse(const Instruction *bari) const
{
@ -3961,34 +4002,13 @@ SchedDataCalculatorGM107::findFirstUse(const Instruction *bari) const
for (insn = bari->next; insn != NULL; insn = next) {
next = insn->next;
for (int s = 0; insn->srcExists(s); ++s) {
const Value *src = insn->src(s).rep();
for (int d = 0; bari->defExists(d); ++d) {
const ValueDef &def = bari->def(d);
int minGPR = def.rep()->reg.data.id;
int maxGPR = minGPR + def.rep()->reg.size / 4 - 1;
for (int s = 0; insn->srcExists(s); ++s)
if (doesInsnWriteTo(bari, insn->getSrc(s)))
return insn;
if (def.getFile() == FILE_GPR) {
if (insn->src(s).getFile() != FILE_GPR ||
src->reg.data.id + src->reg.size / 4 - 1 < minGPR ||
src->reg.data.id > maxGPR)
continue;
return insn;
} else
if (def.getFile() == FILE_PREDICATE) {
if (insn->src(s).getFile() != FILE_PREDICATE ||
src->reg.data.id != minGPR)
continue;
return insn;
}
if (def.getFile() == FILE_FLAGS) {
if (insn->src(s).getFile() != FILE_FLAGS ||
src->reg.data.id != minGPR)
continue;
return insn;
}
}
}
for (int d = 0; insn->defExists(d); ++d)
if (doesInsnWriteTo(bari, insn->getDef(d)))
return insn;
}
return NULL;
}
@ -3999,34 +4019,16 @@ Instruction *
SchedDataCalculatorGM107::findFirstDef(const Instruction *bari) const
{
Instruction *insn, *next;
int minGPR, maxGPR;
if (!bari->srcExists(0))
return NULL;
for (insn = bari->next; insn != NULL; insn = next) {
next = insn->next;
for (int d = 0; insn->defExists(d); ++d) {
const Value *def = insn->def(d).rep();
if (insn->def(d).getFile() != FILE_GPR &&
insn->def(d).getFile() != FILE_FLAGS)
continue;
minGPR = def->reg.data.id;
maxGPR = minGPR + def->reg.size / 4 - 1;
for (int s = 0; bari->srcExists(s); ++s) {
const Value *src = bari->src(s).rep();
if (bari->src(s).getFile() == FILE_FLAGS &&
insn->def(d).getFile() == FILE_FLAGS &&
src->reg.data.id == minGPR)
return insn;
if (bari->src(s).getFile() != FILE_GPR ||
insn->def(d).getFile() != FILE_GPR ||
src->reg.data.id + src->reg.size / 4 - 1 < minGPR ||
src->reg.data.id > maxGPR)
continue;
for (int s = 0; bari->srcExists(s); ++s)
if (doesInsnWriteTo(insn, bari->getSrc(s)))
return insn;
}
}
}
return NULL;
}
@ -4084,7 +4086,8 @@ SchedDataCalculatorGM107::insertBarriers(BasicBlock *bb)
if (need_wr_bar) {
// When the instruction requires to emit a write dependency barrier
// (all which write something at a variable latency), find the next
// instruction which reads the outputs.
// instruction which reads the outputs (or writes to them, potentially
// completing before this insn.
usei = findFirstUse(insn);
// Allocate and emit a new barrier.