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Skip some instructions and PC updates #622

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Skip some instructions and PC updates #622

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c5619fe
Update PC only when needed
chfast Oct 20, 2020
0210b87
Skip block and loop instructions
chfast Oct 20, 2020
39de85b
Skip nop instructions
chfast Oct 20, 2020
d12bd37
Do not omit end instructions
chfast Oct 20, 2020
630272e
Skip end instructions
chfast Oct 20, 2020
8f311f1
Simplify end implementation
chfast Oct 20, 2020
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29 changes: 14 additions & 15 deletions lib/fizzy/execute.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -540,28 +540,27 @@ ExecutionResult execute(Instance& instance, FuncIdx func_idx, const Value* args,

while (true)
{
const auto instruction = *pc++;
const auto instruction = *pc;
switch (instruction)
{
case Instr::unreachable:
goto trap;
case Instr::nop:
case Instr::block:
case Instr::loop:
break;
case Instr::if_:
{
if (stack.pop().as<uint32_t>() != 0)
{
immediates += 2 * sizeof(uint32_t); // Skip the immediates for else instruction.
break;
}
else
{
const auto target_pc = read<uint32_t>(immediates);
const auto target_imm = read<uint32_t>(immediates);

pc = code.instructions.data() + target_pc;
immediates = code.immediates.data() + target_imm;
continue;
}
break;
}
case Instr::else_:
{
Expand All @@ -573,18 +572,16 @@ ExecutionResult execute(Instance& instance, FuncIdx func_idx, const Value* args,
pc = code.instructions.data() + target_pc;
immediates = code.immediates.data() + target_imm;

break;
continue;
}
case Instr::end:
{
// End execution if it's a final end instruction.
if (pc == &code.instructions[code.instructions.size()])
goto end;
break;
assert(pc == &code.instructions[code.instructions.size() - 1]);
goto end;
}
case Instr::br:
case Instr::br_if:
case Instr::return_:
case Instr::return_: // TODO: Replace return with br
{
const auto arity = read<uint32_t>(immediates);

Expand All @@ -596,7 +593,7 @@ ExecutionResult execute(Instance& instance, FuncIdx func_idx, const Value* args,
}

branch(code, stack, pc, immediates, arity);
break;
continue;
}
case Instr::br_table:
{
Expand All @@ -611,7 +608,7 @@ ExecutionResult execute(Instance& instance, FuncIdx func_idx, const Value* args,
immediates += label_idx_offset;

branch(code, stack, pc, immediates, arity);
break;
continue;
}
case Instr::call:
{
Expand Down Expand Up @@ -1557,10 +1554,12 @@ ExecutionResult execute(Instance& instance, FuncIdx func_idx, const Value* args,
default:
FIZZY_UNREACHABLE();
}

++pc;
}

end:
assert(pc == &code.instructions[code.instructions.size()]); // End of code must be reached.
assert(pc == &code.instructions[code.instructions.size() - 1]); // End of code must be reached.
assert(stack.size() == instance.module->get_function_type(func_idx).outputs.size());

return stack.size() != 0 ? ExecutionResult{stack.top()} : Void;
Expand Down
18 changes: 11 additions & 7 deletions lib/fizzy/parser_expr.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -333,6 +333,8 @@ parser_result<Code> parse_expr(const uint8_t* pos, const uint8_t* end, FuncIdx f
}

case Instr::nop:
continue;

case Instr::i32_eqz:
case Instr::i32_eq:
case Instr::i32_ne:
Expand Down Expand Up @@ -466,7 +468,7 @@ parser_result<Code> parse_expr(const uint8_t* pos, const uint8_t* end, FuncIdx f
// Push label with immediates offset after arity.
control_stack.emplace(Instr::block, block_type, static_cast<int>(operand_stack.size()),
code.instructions.size(), code.immediates.size());
break;
continue;
}

case Instr::loop:
Expand All @@ -476,7 +478,7 @@ parser_result<Code> parse_expr(const uint8_t* pos, const uint8_t* end, FuncIdx f

control_stack.emplace(Instr::loop, loop_type, static_cast<int>(operand_stack.size()),
code.instructions.size(), code.immediates.size());
break;
continue;
}

case Instr::if_:
Expand Down Expand Up @@ -538,9 +540,7 @@ parser_result<Code> parse_expr(const uint8_t* pos, const uint8_t* end, FuncIdx f
// In case it's an outermost implicit function block,
// we want br to jump to the final end of the function.
// Otherwise jump to the next instruction after block's end.
const auto target_pc = control_stack.size() == 1 ?
static_cast<uint32_t>(code.instructions.size()) :
static_cast<uint32_t>(code.instructions.size() + 1);
const auto target_pc = static_cast<uint32_t>(code.instructions.size());
const auto target_imm = static_cast<uint32_t>(code.immediates.size());

if (frame.instruction == Instr::if_ || frame.instruction == Instr::else_)
Expand Down Expand Up @@ -569,10 +569,14 @@ parser_result<Code> parse_expr(const uint8_t* pos, const uint8_t* end, FuncIdx f
control_stack.pop(); // Pop the current frame.

if (control_stack.empty())
{
continue_parsing = false;
else if (frame_type.has_value())
break;
}

if (frame_type.has_value())
push_operand(operand_stack, *frame_type);
break;
continue;
}

case Instr::br:
Expand Down