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optimize branching in debug builds

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This commit is contained in:
Folkert 2021-01-26 23:45:41 +01:00
parent aaa103005a
commit e87d8f6449
2 changed files with 88 additions and 56 deletions
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137
compiler/gen/src/llvm/build.rs
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@ -1471,11 +1471,8 @@ pub fn build_exp_expr<'a, 'ctx, 'env>(
let result = builder.build_alloca(ctx.i64_type(), "result");
env.builder.build_switch(
is_null,
else_block,
&[(ctx.bool_type().const_int(1, false), then_block)],
);
env.builder
.build_conditional_branch(is_null, then_block, else_block);
{
env.builder.position_at_end(then_block);
@ -2431,59 +2428,97 @@ fn build_switch_ir<'a, 'ctx, 'env>(
// Build the cases
let mut incoming = Vec::with_capacity_in(branches.len(), arena);
let mut cases = Vec::with_capacity_in(branches.len(), arena);
for (int, _) in branches.iter() {
// Switch constants must all be same type as switch value!
// e.g. this is incorrect, and will trigger a LLVM warning:
//
// switch i8 %apple1, label %default [
// i64 2, label %branch2
// i64 0, label %branch0
// i64 1, label %branch1
// ]
//
// they either need to all be i8, or i64
let int_val = match cond_layout {
Layout::Builtin(Builtin::Usize) => {
ptr_int(env.context, env.ptr_bytes).const_int(*int as u64, false)
if let Layout::Builtin(Builtin::Int1) = cond_layout {
match (branches, default_branch) {
([(0, false_branch)], true_branch) | ([(1, true_branch)], false_branch) => {
let then_block = context.append_basic_block(parent, "then_block");
let else_block = context.append_basic_block(parent, "else_block");
builder.build_conditional_branch(cond, then_block, else_block);
{
builder.position_at_end(then_block);
let branch_val = build_exp_stmt(env, layout_ids, scope, parent, true_branch);
if then_block.get_terminator().is_none() {
builder.build_unconditional_branch(cont_block);
incoming.push((branch_val, then_block));
}
}
{
builder.position_at_end(else_block);
let branch_val = build_exp_stmt(env, layout_ids, scope, parent, false_branch);
if else_block.get_terminator().is_none() {
builder.build_unconditional_branch(cont_block);
incoming.push((branch_val, else_block));
}
}
}
Layout::Builtin(Builtin::Int64) => context.i64_type().const_int(*int as u64, false),
Layout::Builtin(Builtin::Int128) => const_i128(env, *int as i128),
Layout::Builtin(Builtin::Int32) => context.i32_type().const_int(*int as u64, false),
Layout::Builtin(Builtin::Int16) => context.i16_type().const_int(*int as u64, false),
Layout::Builtin(Builtin::Int8) => context.i8_type().const_int(*int as u64, false),
Layout::Builtin(Builtin::Int1) => context.bool_type().const_int(*int as u64, false),
_ => panic!("Can't cast to cond_layout = {:?}", cond_layout),
};
let block = context.append_basic_block(parent, format!("branch{}", int).as_str());
cases.push((int_val, block));
}
let default_block = context.append_basic_block(parent, "default");
builder.build_switch(cond, default_block, &cases);
for ((_, branch_expr), (_, block)) in branches.iter().zip(cases) {
builder.position_at_end(block);
let branch_val = build_exp_stmt(env, layout_ids, scope, parent, branch_expr);
if block.get_terminator().is_none() {
builder.build_unconditional_branch(cont_block);
incoming.push((branch_val, block));
_ => {
dbg!(branches);
unreachable!()
}
}
}
} else {
let default_block = context.append_basic_block(parent, "default");
let mut cases = Vec::with_capacity_in(branches.len(), arena);
// The block for the conditional's default branch.
builder.position_at_end(default_block);
for (int, _) in branches.iter() {
// Switch constants must all be same type as switch value!
// e.g. this is incorrect, and will trigger a LLVM warning:
//
// switch i8 %apple1, label %default [
// i64 2, label %branch2
// i64 0, label %branch0
// i64 1, label %branch1
// ]
//
// they either need to all be i8, or i64
let int_val = match cond_layout {
Layout::Builtin(Builtin::Usize) => {
ptr_int(env.context, env.ptr_bytes).const_int(*int as u64, false)
}
Layout::Builtin(Builtin::Int64) => context.i64_type().const_int(*int as u64, false),
Layout::Builtin(Builtin::Int128) => const_i128(env, *int as i128),
Layout::Builtin(Builtin::Int32) => context.i32_type().const_int(*int as u64, false),
Layout::Builtin(Builtin::Int16) => context.i16_type().const_int(*int as u64, false),
Layout::Builtin(Builtin::Int8) => context.i8_type().const_int(*int as u64, false),
Layout::Builtin(Builtin::Int1) => context.bool_type().const_int(*int as u64, false),
_ => panic!("Can't cast to cond_layout = {:?}", cond_layout),
};
let block = context.append_basic_block(parent, format!("branch{}", int).as_str());
let default_val = build_exp_stmt(env, layout_ids, scope, parent, default_branch);
cases.push((int_val, block));
}
if default_block.get_terminator().is_none() {
builder.build_unconditional_branch(cont_block);
incoming.push((default_val, default_block));
builder.build_switch(cond, default_block, &cases);
for ((_, branch_expr), (_, block)) in branches.iter().zip(cases) {
builder.position_at_end(block);
let branch_val = build_exp_stmt(env, layout_ids, scope, parent, branch_expr);
if block.get_terminator().is_none() {
builder.build_unconditional_branch(cont_block);
incoming.push((branch_val, block));
}
}
// The block for the conditional's default branch.
builder.position_at_end(default_block);
let default_val = build_exp_stmt(env, layout_ids, scope, parent, default_branch);
if default_block.get_terminator().is_none() {
builder.build_unconditional_branch(cont_block);
incoming.push((default_val, default_block));
}
}
// emit merge block