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add comptime eval for some uint comparisons with 0

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closes #55
This commit is contained in:
Andrew Kelley 2017-03-26 14:41:17 -04:00
parent 5bc9feb5cb
commit 3103355805
2 changed files with 52 additions and 0 deletions
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33
src/ir.cpp
View File

@ -7349,6 +7349,39 @@ static TypeTableEntry *ir_analyze_bin_op_cmp(IrAnalyze *ira, IrInstructionBinOp
return ira->codegen->builtin_types.entry_bool;
}
// some comparisons with unsigned numbers can be evaluated
if (resolved_type->id == TypeTableEntryIdInt && !resolved_type->data.integral.is_signed) {
ConstExprValue *known_left_val;
IrBinOp flipped_op_id;
if (value_is_comptime(op1_val)) {
known_left_val = op1_val;
flipped_op_id = op_id;
} else if (value_is_comptime(op2_val)) {
known_left_val = op2_val;
if (op_id == IrBinOpCmpLessThan) {
flipped_op_id = IrBinOpCmpGreaterThan;
} else if (op_id == IrBinOpCmpGreaterThan) {
flipped_op_id = IrBinOpCmpLessThan;
} else if (op_id == IrBinOpCmpLessOrEq) {
flipped_op_id = IrBinOpCmpGreaterOrEq;
} else if (op_id == IrBinOpCmpGreaterOrEq) {
flipped_op_id = IrBinOpCmpLessOrEq;
} else {
flipped_op_id = op_id;
}
} else {
known_left_val = nullptr;
}
if (known_left_val != nullptr && known_left_val->data.x_bignum.data.x_uint == 0 &&
(flipped_op_id == IrBinOpCmpLessOrEq || flipped_op_id == IrBinOpCmpGreaterThan))
{
bool answer = (flipped_op_id == IrBinOpCmpLessOrEq);
ConstExprValue *out_val = ir_build_const_from(ira, &bin_op_instruction->base);
out_val->data.x_bool = answer;
return ira->codegen->builtin_types.entry_bool;
}
}
ir_build_bin_op_from(&ira->new_irb, &bin_op_instruction->base, op_id,
casted_op1, casted_op2, bin_op_instruction->safety_check_on);

19
test/cases/eval.zig
View File

@ -265,3 +265,22 @@ fn modifySomeBytes(bytes: []u8) {
bytes[0] = 'a';
bytes[9] = 'b';
}
test "comparisons 0 <= uint and 0 > uint should be comptime" {
testCompTimeUIntComparisons(1234);
}
fn testCompTimeUIntComparisons(x: u32) {
if (!(0 <= x)) {
@compileError("this condition should be comptime known");
}
if (0 > x) {
@compileError("this condition should be comptime known");
}
if (!(x >= 0)) {
@compileError("this condition should be comptime known");
}
if (x < 0) {
@compileError("this condition should be comptime known");
}
}