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if statements can be const expr evaluated

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also introduce error for unnecessary if statement
but if the condition depends on a compile variable, then
the if statement is OK
This commit is contained in:
Andrew Kelley
2016-02-09 18:50:53 -07:00
parent f45c374664
commit d8f6388b63
7 changed files with 387 additions and 379 deletions
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119
src/codegen.cpp
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@@ -1737,81 +1737,60 @@ static LLVMValueRef gen_return_expr(CodeGen *g, AstNode *node) {
zig_unreachable();
}
static LLVMValueRef gen_defer(CodeGen *g, AstNode *node) {
assert(node->type == NodeTypeDefer);
return nullptr;
}
static LLVMValueRef gen_if_bool_expr_raw(CodeGen *g, AstNode *source_node, LLVMValueRef cond_value,
AstNode *then_node, AstNode *else_node)
{
assert(then_node);
assert(else_node);
TypeTableEntry *then_type = get_expr_type(then_node);
bool use_expr_value = (then_type->id != TypeTableEntryIdUnreachable &&
then_type->id != TypeTableEntryIdVoid);
TypeTableEntry *else_type = get_expr_type(else_node);
if (else_node) {
LLVMBasicBlockRef then_block = LLVMAppendBasicBlock(g->cur_fn->fn_value, "Then");
LLVMBasicBlockRef else_block = LLVMAppendBasicBlock(g->cur_fn->fn_value, "Else");
LLVMBasicBlockRef endif_block;
bool then_endif_reachable = get_expr_type(then_node)->id != TypeTableEntryIdUnreachable;
bool else_endif_reachable = get_expr_type(else_node)->id != TypeTableEntryIdUnreachable;
if (then_endif_reachable || else_endif_reachable) {
endif_block = LLVMAppendBasicBlock(g->cur_fn->fn_value, "EndIf");
}
LLVMBuildCondBr(g->builder, cond_value, then_block, else_block);
LLVMPositionBuilderAtEnd(g->builder, then_block);
LLVMValueRef then_expr_result = gen_expr(g, then_node);
if (then_endif_reachable) {
LLVMBuildBr(g->builder, endif_block);
}
LLVMBasicBlockRef after_then_block = LLVMGetInsertBlock(g->builder);
LLVMPositionBuilderAtEnd(g->builder, else_block);
LLVMValueRef else_expr_result = gen_expr(g, else_node);
if (else_endif_reachable) {
LLVMBuildBr(g->builder, endif_block);
}
LLVMBasicBlockRef after_else_block = LLVMGetInsertBlock(g->builder);
if (then_endif_reachable || else_endif_reachable) {
LLVMPositionBuilderAtEnd(g->builder, endif_block);
if (use_expr_value) {
LLVMValueRef phi = LLVMBuildPhi(g->builder, LLVMTypeOf(then_expr_result), "");
LLVMValueRef incoming_values[2] = {then_expr_result, else_expr_result};
LLVMBasicBlockRef incoming_blocks[2] = {after_then_block, after_else_block};
LLVMAddIncoming(phi, incoming_values, incoming_blocks, 2);
return phi;
}
}
return nullptr;
}
assert(!use_expr_value || then_type->id == TypeTableEntryIdErrorUnion);
bool use_then_value = type_has_bits(then_type);
bool use_else_value = type_has_bits(else_type);
LLVMBasicBlockRef then_block = LLVMAppendBasicBlock(g->cur_fn->fn_value, "Then");
LLVMBasicBlockRef endif_block = LLVMAppendBasicBlock(g->cur_fn->fn_value, "EndIf");
LLVMBasicBlockRef else_block = LLVMAppendBasicBlock(g->cur_fn->fn_value, "Else");
LLVMBuildCondBr(g->builder, cond_value, then_block, endif_block);
LLVMBasicBlockRef endif_block;
bool then_endif_reachable = then_type->id != TypeTableEntryIdUnreachable;
bool else_endif_reachable = else_type->id != TypeTableEntryIdUnreachable;
if (then_endif_reachable || else_endif_reachable) {
endif_block = LLVMAppendBasicBlock(g->cur_fn->fn_value, "EndIf");
}
LLVMBuildCondBr(g->builder, cond_value, then_block, else_block);
LLVMPositionBuilderAtEnd(g->builder, then_block);
gen_expr(g, then_node);
if (get_expr_type(then_node)->id != TypeTableEntryIdUnreachable)
LLVMValueRef then_expr_result = gen_expr(g, then_node);
if (then_endif_reachable) {
LLVMBuildBr(g->builder, endif_block);
LLVMPositionBuilderAtEnd(g->builder, endif_block);
if (use_expr_value) {
return LLVMConstNull(g->err_tag_type->type_ref);
} else {
return nullptr;
}
LLVMBasicBlockRef after_then_block = LLVMGetInsertBlock(g->builder);
LLVMPositionBuilderAtEnd(g->builder, else_block);
LLVMValueRef else_expr_result = gen_expr(g, else_node);
if (else_endif_reachable) {
LLVMBuildBr(g->builder, endif_block);
}
LLVMBasicBlockRef after_else_block = LLVMGetInsertBlock(g->builder);
if (then_endif_reachable || else_endif_reachable) {
LLVMPositionBuilderAtEnd(g->builder, endif_block);
if (use_then_value && use_else_value) {
LLVMValueRef phi = LLVMBuildPhi(g->builder, LLVMTypeOf(then_expr_result), "");
LLVMValueRef incoming_values[2] = {then_expr_result, else_expr_result};
LLVMBasicBlockRef incoming_blocks[2] = {after_then_block, after_else_block};
LLVMAddIncoming(phi, incoming_values, incoming_blocks, 2);
return phi;
} else if (use_then_value) {
return then_expr_result;
} else if (use_else_value) {
return else_expr_result;
}
}
return nullptr;
}
static LLVMValueRef gen_if_bool_expr(CodeGen *g, AstNode *node) {
@@ -1866,14 +1845,6 @@ static LLVMValueRef gen_if_var_expr(CodeGen *g, AstNode *node) {
return return_value;
}
//static int block_exit_path_count(BlockContext *block_context) {
// int sum = 0;
// for (int i = 0; i < BlockExitPathCount; i += 1) {
// sum += block_context->block_exit_paths[i] ? 1 : 0;
// }
// return sum;
//}
static LLVMValueRef gen_block(CodeGen *g, AstNode *block_node, TypeTableEntry *implicit_return_type) {
assert(block_node->type == NodeTypeBlock);
@@ -2553,7 +2524,8 @@ static LLVMValueRef gen_expr(CodeGen *g, AstNode *node) {
case NodeTypeReturnExpr:
return gen_return_expr(g, node);
case NodeTypeDefer:
return gen_defer(g, node);
// nothing to do
return nullptr;
case NodeTypeVariableDeclaration:
return gen_var_decl_expr(g, node);
case NodeTypePrefixOpExpr:
@@ -3191,6 +3163,7 @@ static const CIntTypeInfo c_int_type_infos[] = {
static int get_c_type_size_in_bits(CodeGen *g, CIntType id) {
// TODO other architectures besides x86_64
// other operating systems besides linux
switch (id) {
case CIntTypeShort:
case CIntTypeUShort:
@@ -3203,6 +3176,8 @@ static int get_c_type_size_in_bits(CodeGen *g, CIntType id) {
case CIntTypeLongLong:
case CIntTypeULongLong:
return 64;
case CIntTypeCount:
zig_unreachable();
}
zig_unreachable();
}