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Avoid recording computed data references that are the same as the last constant value. #335

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Aug 5, 2023
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Avoid recording computed data references that are the same as the last constant value. #335

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64 changes: 49 additions & 15 deletions pyvex_c/analysis.c
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Original file line number Diff line number Diff line change
Expand Up @@ -326,7 +326,7 @@ void record_data_reference(
lift_r->data_ref_count++;
}

void record_const(
Addr record_const(
VEXLiftResult *lift_r,
IRExpr *const_expr,
Int size,
Expand All @@ -338,14 +338,15 @@ void record_const(
if (const_expr->tag != Iex_Const) {
// Why are you calling me?
assert (const_expr->tag == Iex_Const);
return;
return -1;
}

Addr addr = get_value_from_const_expr(const_expr->Iex.Const.con);
if (addr != next_inst_addr) {
record_data_reference(lift_r, addr, size, data_type, stmt_idx, inst_addr);
return addr;
}

return -1;
}


Expand Down Expand Up @@ -541,6 +542,10 @@ void collect_data_references(
HashHW* env = newHHW();
TmpValue *tmps = NULL;
TmpValue tmp_backingstore[1024];
// Record the last legitimate constant value. We do not record RdTmp or BinOp results
// if they are the same as the last constant.
UInt last_const_value = 0;

if (irsb->tyenv->types_used > 1024) {
tmps = malloc(irsb->tyenv->types_used * sizeof(TmpValue));
} else {
Expand Down Expand Up @@ -593,7 +598,10 @@ void collect_data_references(
if (data->Iex.Load.addr->tag == Iex_Const) {
Int size;
size = sizeofIRType(typeOfIRTemp(irsb->tyenv, stmt->Ist.WrTmp.tmp));
record_const(lift_r, data->Iex.Load.addr, size, Dt_Integer, i, inst_addr, next_inst_addr);
Addr v = record_const(lift_r, data->Iex.Load.addr, size, Dt_Integer, i, inst_addr, next_inst_addr);
if (v != -1 && v != next_inst_addr) {
last_const_value = v;
}
// Load the value if it might be a constant pointer...
if (load_from_ro_regions && guest == VexArchARM && size == 4) {
UInt value;
Expand All @@ -608,7 +616,9 @@ void collect_data_references(
// The source tmp exists
Int size;
size = sizeofIRType(typeOfIRTemp(irsb->tyenv, stmt->Ist.WrTmp.tmp));
record_data_reference(lift_r, tmps[rdtmp].value, size, Dt_Integer, i, inst_addr);
if (tmps[rdtmp].value != last_const_value) {
record_data_reference(lift_r, tmps[rdtmp].value, size, Dt_Integer, i, inst_addr);
}
if (load_from_ro_regions)
if (guest == VexArchARM && size == 4 ||
guest == VexArchMIPS32 && size == 4 ||
Expand All @@ -633,7 +643,9 @@ void collect_data_references(
addr &= 0xffffffff;
}
if (addr != next_inst_addr) {
record_data_reference(lift_r, addr, 0, Dt_Unknown, i, inst_addr);
if (addr != last_const_value) {
record_data_reference(lift_r, addr, 0, Dt_Unknown, i, inst_addr);
}
}
} else {
// Do the calculation
Expand All @@ -646,7 +658,9 @@ void collect_data_references(
if (data->Iex.Binop.op == Iop_Add32) {
value &= 0xffffffff;
}
record_data_reference(lift_r, value, 0, Dt_Unknown, i, inst_addr);
if (value != last_const_value) {
record_data_reference(lift_r, value, 0, Dt_Unknown, i, inst_addr);
}
tmps[stmt->Ist.WrTmp.tmp].used = 1;
tmps[stmt->Ist.WrTmp.tmp].value = value;
}
Expand All @@ -659,7 +673,9 @@ void collect_data_references(
if (data->Iex.Binop.op == Iop_Add32) {
value &= 0xffffffff;
}
record_data_reference(lift_r, value, 0, Dt_Unknown, i, inst_addr);
if (value != last_const_value) {
record_data_reference(lift_r, value, 0, Dt_Unknown, i, inst_addr);
}
tmps[stmt->Ist.WrTmp.tmp].used = 1;
tmps[stmt->Ist.WrTmp.tmp].value = value;
}
Expand All @@ -672,13 +688,17 @@ void collect_data_references(
if (data->Iex.Binop.op == Iop_Add32) {
value &= 0xffffffff;
}
record_data_reference(lift_r, value, 0, Dt_Unknown, i, inst_addr);
if (value != last_const_value) {
record_data_reference(lift_r, value, 0, Dt_Unknown, i, inst_addr);
}
tmps[stmt->Ist.WrTmp.tmp].used = 1;
tmps[stmt->Ist.WrTmp.tmp].value = value;
}
if (arg2->tag == Iex_Const) {
ULong arg2_value = get_value_from_const_expr(arg2->Iex.Const.con);
record_data_reference(lift_r, arg2_value, 0, Dt_Unknown, i, inst_addr);
if (arg2_value != last_const_value) {
record_data_reference(lift_r, arg2_value, 0, Dt_Unknown, i, inst_addr);
}
}
if (arg1->tag == Iex_RdTmp
&& tmps[arg1->Iex.RdTmp.tmp].used
Expand All @@ -698,16 +718,25 @@ void collect_data_references(
else {
// Normal binary operations
if (data->Iex.Binop.arg1->tag == Iex_Const) {
record_const(lift_r, data->Iex.Binop.arg1, 0, Dt_Unknown, i, inst_addr, next_inst_addr);
Addr v = record_const(lift_r, data->Iex.Binop.arg1, 0, Dt_Unknown, i, inst_addr, next_inst_addr);
if (v != -1 && v != next_inst_addr) {
last_const_value = v;
}
}
if (data->Iex.Binop.arg2->tag == Iex_Const) {
record_const(lift_r, data->Iex.Binop.arg2, 0, Dt_Unknown, i, inst_addr, next_inst_addr);
Addr v = record_const(lift_r, data->Iex.Binop.arg2, 0, Dt_Unknown, i, inst_addr, next_inst_addr);
if (v != -1 && v != next_inst_addr) {
last_const_value = v;
}
}
}
break;
case Iex_Const:
{
record_const(lift_r, data, 0, Dt_Unknown, i, inst_addr, next_inst_addr);
Addr v = record_const(lift_r, data, 0, Dt_Unknown, i, inst_addr, next_inst_addr);
if (v != -1 && v != next_inst_addr) {
last_const_value = v;
}
tmps[stmt->Ist.WrTmp.tmp].used = 1;
tmps[stmt->Ist.WrTmp.tmp].value = get_value_from_const_expr(data->Iex.Const.con);
}
Expand Down Expand Up @@ -749,7 +778,10 @@ void collect_data_references(

IRExpr *data = stmt->Ist.Put.data;
if (data->tag == Iex_Const) {
record_const(lift_r, data, 0, Dt_Unknown, i, inst_addr, next_inst_addr);
Addr v = record_const(lift_r, data, 0, Dt_Unknown, i, inst_addr, next_inst_addr);
if (v != -1 && v != next_inst_addr) {
last_const_value = v;
}
UInt key = mk_key_GetPut(stmt->Ist.Put.offset, typeOfIRExpr(irsb->tyenv, data));
addToHHW(env, key, get_value_from_const_expr(data->Iex.Const.con));
} else if (data->tag == Iex_RdTmp) {
Expand All @@ -759,7 +791,9 @@ void collect_data_references(
UInt key = mk_key_GetPut(stmt->Ist.Put.offset, data_type);
ULong value = tmps[data->Iex.RdTmp.tmp].value;
addToHHW(env, key, value);
record_data_reference(lift_r, value, 0, Dt_Integer, i, inst_addr);
if (value != last_const_value) {
record_data_reference(lift_r, value, 0, Dt_Integer, i, inst_addr);
}
}
}
}
Expand Down
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