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Fixing const propagated DID_CARRY.

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This commit is contained in:
Ben Vanik
2014-05-30 20:09:00 -07:00
parent d65b5801f8
commit 0b42c72ec5
5 changed files with 74 additions and 10 deletions
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49
src/alloy/compiler/passes/constant_propagation_pass.cc
View File

@@ -43,6 +43,14 @@ int ConstantPropagationPass::Run(HIRBuilder* builder) {
// v1 = add 1000, 1000
// store_context +200, 2000
// A DCE run after this should clean up any of the values no longer needed.
//
// Special care needs to be taken with paired instructions. For example,
// DID_CARRY needs to be set as a constant:
// v1 = sub.2 20, 1
// v2 = did_carry v1
// should become:
// v1 = 19
// v2 = 0
Block* block = builder->first_block();
while (block) {
@@ -252,19 +260,41 @@ int ConstantPropagationPass::Run(HIRBuilder* builder) {
}
break;
case OPCODE_DID_CARRY:
XEASSERT(!i->src1.value->IsConstant());
break;
case OPCODE_DID_OVERFLOW:
XEASSERT(!i->src1.value->IsConstant());
break;
case OPCODE_DID_SATURATE:
XEASSERT(!i->src1.value->IsConstant());
break;
case OPCODE_ADD:
if (i->src1.value->IsConstant() && i->src2.value->IsConstant()) {
v->set_from(i->src1.value);
v->Add(i->src2.value);
bool did_carry = v->Add(i->src2.value);
bool propagate_carry = !!(i->flags & ARITHMETIC_SET_CARRY);
i->Remove();
// If carry is set find the DID_CARRY and fix it.
if (propagate_carry) {
PropagateCarry(v, did_carry);
}
}
break;
// TODO(benvanik): ADD_CARRY
// TODO(benvanik): ADD_CARRY (w/ ARITHMETIC_SET_CARRY)
case OPCODE_SUB:
if (i->src1.value->IsConstant() && i->src2.value->IsConstant()) {
v->set_from(i->src1.value);
v->Sub(i->src2.value);
bool did_carry = v->Sub(i->src2.value);
bool propagate_carry = !!(i->flags & ARITHMETIC_SET_CARRY);
i->Remove();
// If carry is set find the DID_CARRY and fix it.
if (propagate_carry) {
PropagateCarry(v, did_carry);
}
}
break;
case OPCODE_MUL:
@@ -393,3 +423,16 @@ int ConstantPropagationPass::Run(HIRBuilder* builder) {
return 0;
}
void ConstantPropagationPass::PropagateCarry(hir::Value* v, bool did_carry) {
auto next = v->use_head;
while (next) {
auto use = next;
next = use->next;
if (use->instr->opcode == &OPCODE_DID_CARRY_info) {
// Replace carry value.
use->instr->dest->set_constant(did_carry ? 1 : 0);
use->instr->Remove();
}
}
}

1
src/alloy/compiler/passes/constant_propagation_pass.h
View File

@@ -26,6 +26,7 @@ public:
virtual int Run(hir::HIRBuilder* builder);
private:
void PropagateCarry(hir::Value* v, bool did_carry);
};