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ir: Implement more safety checks for shl/shr

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The checks are now valid on types whose size is not a power of two.

Closes #2096
This commit is contained in:
LemonBoy
2020-03-10 20:54:05 +01:00
parent 9c4dc7b1bb
commit 300fceac6e
5 changed files with 120 additions and 27 deletions
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32
src/codegen.cpp
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@@ -974,6 +974,8 @@ static Buf *panic_msg_buf(PanicMsgId msg_id) {
return buf_create_from_str("resumed a non-suspended function");
case PanicMsgIdBadSentinel:
return buf_create_from_str("sentinel mismatch");
case PanicMsgIdShxTooBigRhs:
return buf_create_from_str("shift amount is greater than the type size");
}
zig_unreachable();
}
@@ -2841,6 +2843,26 @@ static LLVMValueRef gen_rem(CodeGen *g, bool want_runtime_safety, bool want_fast
}
static void gen_shift_rhs_check(CodeGen *g, ZigType *lhs_type, ZigType *rhs_type, LLVMValueRef value) {
// We only check if the rhs value of the shift expression is greater or
// equal to the number of bits of the lhs if it's not a power of two,
// otherwise the check is useful as the allowed values are limited by the
// operand type itself
if (!is_power_of_2(lhs_type->data.integral.bit_count)) {
LLVMValueRef bit_count_value = LLVMConstInt(get_llvm_type(g, rhs_type),
lhs_type->data.integral.bit_count, false);
LLVMValueRef less_than_bit = LLVMBuildICmp(g->builder, LLVMIntULT, value, bit_count_value, "");
LLVMBasicBlockRef fail_block = LLVMAppendBasicBlock(g->cur_fn_val, "CheckFail");
LLVMBasicBlockRef ok_block = LLVMAppendBasicBlock(g->cur_fn_val, "CheckOk");
LLVMBuildCondBr(g->builder, less_than_bit, ok_block, fail_block);
LLVMPositionBuilderAtEnd(g->builder, fail_block);
gen_safety_crash(g, PanicMsgIdShxTooBigRhs);
LLVMPositionBuilderAtEnd(g->builder, ok_block);
}
}
static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable,
IrInstGenBinOp *bin_op_instruction)
{
@@ -2949,6 +2971,11 @@ static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable,
{
assert(scalar_type->id == ZigTypeIdInt);
LLVMValueRef op2_casted = gen_widen_or_shorten(g, false, op2->value->type, scalar_type, op2_value);
if (want_runtime_safety) {
gen_shift_rhs_check(g, scalar_type, op2->value->type, op2_value);
}
bool is_sloppy = (op_id == IrBinOpBitShiftLeftLossy);
if (is_sloppy) {
return LLVMBuildShl(g->builder, op1_value, op2_casted, "");
@@ -2965,6 +2992,11 @@ static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable,
{
assert(scalar_type->id == ZigTypeIdInt);
LLVMValueRef op2_casted = gen_widen_or_shorten(g, false, op2->value->type, scalar_type, op2_value);
if (want_runtime_safety) {
gen_shift_rhs_check(g, scalar_type, op2->value->type, op2_value);
}
bool is_sloppy = (op_id == IrBinOpBitShiftRightLossy);
if (is_sloppy) {
if (scalar_type->data.integral.is_signed) {