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add debug safety for left shifting

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See #46
This commit is contained in:
Andrew Kelley
2016-05-06 15:46:38 -07:00
parent 0c96920172
commit 100802cdc0
4 changed files with 79 additions and 5 deletions
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43
src/codegen.cpp
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@@ -440,7 +440,7 @@ static LLVMValueRef gen_cmp_exchange(CodeGen *g, AstNode *node) {
LLVMAtomicOrdering failure_order = to_LLVMAtomicOrdering((AtomicOrder)failure_order_val->data.x_enum.tag);
LLVMValueRef result_val = ZigLLVMBuildCmpXchg(g->builder, ptr_val, cmp_val, new_val,
success_order, failure_order, "");
success_order, failure_order);
return LLVMBuildExtractValue(g->builder, result_val, 1, "");
}
@@ -1309,6 +1309,36 @@ static LLVMValueRef gen_overflow_op(CodeGen *g, TypeTableEntry *type_entry, AddS
return result;
}
static LLVMValueRef gen_overflow_shl_op(CodeGen *g, TypeTableEntry *type_entry,
LLVMValueRef val1, LLVMValueRef val2)
{
// for unsigned left shifting, we do the wrapping shift, then logically shift
// right the same number of bits
// if the values don't match, we have an overflow
// for signed left shifting we do the same except arithmetic shift right
assert(type_entry->id == TypeTableEntryIdInt);
LLVMValueRef result = LLVMBuildShl(g->builder, val1, val2, "");
LLVMValueRef orig_val;
if (type_entry->data.integral.is_signed) {
orig_val = LLVMBuildAShr(g->builder, result, val2, "");
} else {
orig_val = LLVMBuildLShr(g->builder, result, val2, "");
}
LLVMValueRef ok_bit = LLVMBuildICmp(g->builder, LLVMIntEQ, val1, orig_val, "");
LLVMBasicBlockRef ok_block = LLVMAppendBasicBlock(g->cur_fn->fn_value, "OverflowOk");
LLVMBasicBlockRef fail_block = LLVMAppendBasicBlock(g->cur_fn->fn_value, "OverflowFail");
LLVMBuildCondBr(g->builder, ok_bit, ok_block, fail_block);
LLVMPositionBuilderAtEnd(g->builder, fail_block);
gen_debug_safety_crash(g);
LLVMPositionBuilderAtEnd(g->builder, ok_block);
return result;
}
static LLVMValueRef gen_prefix_op_expr(CodeGen *g, AstNode *node) {
assert(node->type == NodeTypePrefixOpExpr);
assert(node->data.prefix_op_expr.primary_expr);
@@ -1484,7 +1514,16 @@ static LLVMValueRef gen_arithmetic_bin_op(CodeGen *g, AstNode *source_node,
case BinOpTypeBitShiftLeft:
case BinOpTypeAssignBitShiftLeft:
set_debug_source_node(g, source_node);
return LLVMBuildShl(g->builder, val1, val2, "");
assert(op1_type->id == TypeTableEntryIdInt);
if (op1_type->data.integral.is_wrapping) {
return LLVMBuildShl(g->builder, val1, val2, "");
} else if (want_debug_safety(g, source_node)) {
return gen_overflow_shl_op(g, op1_type, val1, val2);
} else if (op1_type->data.integral.is_signed) {
return ZigLLVMBuildNSWShl(g->builder, val1, val2, "");
} else {
return ZigLLVMBuildNUWShl(g->builder, val1, val2, "");
}
case BinOpTypeBitShiftRight:
case BinOpTypeAssignBitShiftRight:
assert(op1_type->id == TypeTableEntryIdInt);