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@floatToInt now has safety-checked undefined behavior

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when the integer part does not fit in the destination integer type

 * Also fix incorrect safety triggered for integer casting an
   `i32` to a `u7`. closes #1138
 * adds compiler-rt function: `__floatuntidf`
This commit is contained in:
Andrew Kelley
2018-06-19 16:06:10 -04:00
parent 0b92d689d0
commit c7804277bf
12 changed files with 291 additions and 9 deletions
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36
src/codegen.cpp
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@@ -865,6 +865,8 @@ static Buf *panic_msg_buf(PanicMsgId msg_id) {
return buf_create_from_str("access of inactive union field");
case PanicMsgIdBadEnumValue:
return buf_create_from_str("invalid enum value");
case PanicMsgIdFloatToInt:
return buf_create_from_str("integer part of floating point value out of bounds");
}
zig_unreachable();
}
@@ -1671,7 +1673,7 @@ static LLVMValueRef gen_widen_or_shorten(CodeGen *g, bool want_runtime_safety, T
return trunc_val;
}
LLVMValueRef orig_val;
if (actual_type->data.integral.is_signed) {
if (wanted_type->data.integral.is_signed) {
orig_val = LLVMBuildSExt(g->builder, trunc_val, actual_type->type_ref, "");
} else {
orig_val = LLVMBuildZExt(g->builder, trunc_val, actual_type->type_ref, "");
@@ -2546,15 +2548,41 @@ static LLVMValueRef ir_render_cast(CodeGen *g, IrExecutable *executable,
} else {
return LLVMBuildUIToFP(g->builder, expr_val, wanted_type->type_ref, "");
}
case CastOpFloatToInt:
case CastOpFloatToInt: {
assert(wanted_type->id == TypeTableEntryIdInt);
ZigLLVMSetFastMath(g->builder, ir_want_fast_math(g, &cast_instruction->base));
bool want_safety = ir_want_runtime_safety(g, &cast_instruction->base);
LLVMValueRef result;
if (wanted_type->data.integral.is_signed) {
return LLVMBuildFPToSI(g->builder, expr_val, wanted_type->type_ref, "");
result = LLVMBuildFPToSI(g->builder, expr_val, wanted_type->type_ref, "");
} else {
return LLVMBuildFPToUI(g->builder, expr_val, wanted_type->type_ref, "");
result = LLVMBuildFPToUI(g->builder, expr_val, wanted_type->type_ref, "");
}
if (want_safety) {
LLVMValueRef back_to_float;
if (wanted_type->data.integral.is_signed) {
back_to_float = LLVMBuildSIToFP(g->builder, result, LLVMTypeOf(expr_val), "");
} else {
back_to_float = LLVMBuildUIToFP(g->builder, result, LLVMTypeOf(expr_val), "");
}
LLVMValueRef difference = LLVMBuildFSub(g->builder, expr_val, back_to_float, "");
LLVMValueRef one_pos = LLVMConstReal(LLVMTypeOf(expr_val), 1.0f);
LLVMValueRef one_neg = LLVMConstReal(LLVMTypeOf(expr_val), -1.0f);
LLVMValueRef ok_bit_pos = LLVMBuildFCmp(g->builder, LLVMRealOLT, difference, one_pos, "");
LLVMValueRef ok_bit_neg = LLVMBuildFCmp(g->builder, LLVMRealOGT, difference, one_neg, "");
LLVMValueRef ok_bit = LLVMBuildAnd(g->builder, ok_bit_pos, ok_bit_neg, "");
LLVMBasicBlockRef ok_block = LLVMAppendBasicBlock(g->cur_fn_val, "FloatCheckOk");
LLVMBasicBlockRef bad_block = LLVMAppendBasicBlock(g->cur_fn_val, "FloatCheckFail");
LLVMBuildCondBr(g->builder, ok_bit, ok_block, bad_block);
LLVMPositionBuilderAtEnd(g->builder, bad_block);
gen_safety_crash(g, PanicMsgIdFloatToInt);
LLVMPositionBuilderAtEnd(g->builder, ok_block);
}
return result;
}
case CastOpBoolToInt:
assert(wanted_type->id == TypeTableEntryIdInt);
assert(actual_type->id == TypeTableEntryIdBool);