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add support for $mul, $div, $divfloor, $mod, $modfloor, $pow in functional backend

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This commit is contained in:
Emily Schmidt 2024-07-04 16:58:07 +01:00
parent 50f487e08c
commit 1b2986f7fb
5 changed files with 177 additions and 11 deletions
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73
kernel/functionalir.cc
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@ -37,6 +37,15 @@ class CellSimplifier {
return factory.mux(lower_b, factory.constant(RTLIL::Const(y_width, new_width)), overflow, new_width);
}
}
T sign(T a, int a_width) {
return factory.slice(a, a_width, a_width - 1, 1);
}
T neg_if(T a, int a_width, T s) {
return factory.mux(a, factory.unary_minus(a, a_width), s, a_width);
}
T abs(T a, int a_width) {
return neg_if(a, a_width, sign(a, a_width));
}
public:
T reduce_or(T a, int width) {
if (width == 1)
@ -71,6 +80,23 @@ public:
return factory.bitwise_or(aa, bb, width);
}
CellSimplifier(Factory &f) : factory(f) {}
private:
T handle_pow(T a0, int a_width, T b, int b_width, int y_width, bool is_signed) {
T a = extend(a0, a_width, y_width, is_signed);
T r = factory.constant(Const(1, y_width));
for(int i = 0; i < b_width; i++) {
T b_bit = factory.slice(b, b_width, i, 1);
r = factory.mux(r, factory.mul(r, a, y_width), b_bit, y_width);
a = factory.mul(a, a, y_width);
}
if (is_signed) {
T a_ge_1 = factory.unsigned_greater_than(abs(a0, a_width), factory.constant(Const(1, a_width)), a_width);
T zero_result = factory.bitwise_and(a_ge_1, sign(b, b_width), 1);
r = factory.mux(r, factory.constant(Const(0, y_width)), zero_result, y_width);
}
return r;
}
public:
T handle(IdString cellType, dict<IdString, Const> parameters, dict<IdString, T> inputs)
{
int a_width = parameters.at(ID(A_WIDTH), Const(-1)).as_int();
@ -78,7 +104,7 @@ public:
int y_width = parameters.at(ID(Y_WIDTH), Const(-1)).as_int();
bool a_signed = parameters.at(ID(A_SIGNED), Const(0)).as_bool();
bool b_signed = parameters.at(ID(B_SIGNED), Const(0)).as_bool();
if(cellType.in({ID($add), ID($sub), ID($and), ID($or), ID($xor), ID($xnor)})){
if(cellType.in({ID($add), ID($sub), ID($and), ID($or), ID($xor), ID($xnor), ID($mul)})){
bool is_signed = a_signed && b_signed;
T a = extend(inputs.at(ID(A)), a_width, y_width, is_signed);
T b = extend(inputs.at(ID(B)), b_width, y_width, is_signed);
@ -86,6 +112,8 @@ public:
return factory.add(a, b, y_width);
else if(cellType == ID($sub))
return factory.sub(a, b, y_width);
else if(cellType == ID($mul))
return factory.mul(a, b, y_width);
else if(cellType == ID($and))
return factory.bitwise_and(a, b, y_width);
else if(cellType == ID($or))
@ -160,7 +188,7 @@ public:
T b = inputs.at(ID(B));
T shr = logical_shift_right(a, b, width, b_width);
if(b_signed) {
T sign_b = factory.slice(b, b_width, b_width - 1, 1);
T sign_b = sign(b, b_width);
T shl = logical_shift_left(a, factory.unary_minus(b, b_width), width, b_width);
T y = factory.mux(shr, shl, sign_b, width);
return extend(y, width, y_width, false);
@ -182,7 +210,46 @@ public:
int offset = parameters.at(ID(OFFSET)).as_int();
T a = inputs.at(ID(A));
return factory.slice(a, a_width, offset, y_width);
}else{
}else if(cellType.in({ID($div), ID($mod), ID($divfloor), ID($modfloor)})) {
int width = max(a_width, b_width);
bool is_signed = a_signed && b_signed;
T a = extend(inputs.at(ID(A)), a_width, width, is_signed);
T b = extend(inputs.at(ID(B)), b_width, width, is_signed);
if(is_signed) {
if(cellType == ID($div)) {
T abs_y = factory.unsigned_div(abs(a, width), abs(b, width), width);
T out_sign = factory.not_equal(sign(a, width), sign(b, width), 1);
return neg_if(extend(abs_y, width, y_width, true), y_width, out_sign);
} else if(cellType == ID($mod)) {
T abs_y = factory.unsigned_mod(abs(a, width), abs(b, width), width);
return neg_if(extend(abs_y, width, y_width, true), y_width, sign(a, width));
} else if(cellType == ID($divfloor)) {
T b_sign = sign(b, width);
T a1 = neg_if(a, width, b_sign);
T b1 = neg_if(b, width, b_sign);
T a1_sign = sign(a1, width);
T a2 = factory.mux(a1, factory.bitwise_not(a1, width), a1_sign, width);
T y1 = factory.unsigned_div(a2, b1, width);
T y2 = factory.mux(y1, factory.bitwise_not(y1, width), a1_sign, width);
return extend(y2, width, y_width, true);
} else if(cellType == ID($modfloor)) {
T abs_b = abs(b, width);
T abs_y = factory.unsigned_mod(abs(a, width), abs_b, width);
T flip_y = factory.bitwise_and(factory.bitwise_xor(sign(a, width), sign(b, width), 1), factory.reduce_or(abs_y, width), 1);
T y_flipped = factory.mux(abs_y, factory.sub(abs_b, abs_y, width), flip_y, width);
T y = neg_if(y_flipped, width, sign(b, b_width));
return extend(y, width, y_width, true);
} else
log_error("unhandled cell in CellSimplifier %s\n", cellType.c_str());
} else {
if(cellType.in({ID($mod), ID($modfloor)}))
return extend(factory.unsigned_mod(a, b, width), width, y_width, false);
else
return extend(factory.unsigned_div(a, b, width), width, y_width, false);
}
} else if(cellType == ID($pow)) {
return handle_pow(inputs.at(ID(A)), a_width, inputs.at(ID(B)), b_width, y_width, a_signed && b_signed);
} else{
log_error("unhandled cell in CellSimplifier %s\n", cellType.c_str());
}
}