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Auto merge of #94123 - bjorn3:cg_ssa_singleton_builder, r=tmiasko
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Partially move cg_ssa towards using a single builder

Not all codegen backends can handle hopping between blocks well. For example Cranelift requires blocks to be terminated before switching to building a new block. Rust-gpu requires a `RefCell` to allow hopping between blocks and cg_gcc currently has a buggy implementation of hopping between blocks. This PR reduces the amount of cases where cg_ssa switches between blocks before they are finished and mostly fixes the block hopping in cg_gcc. (~~only `scalar_to_backend` doesn't handle it correctly yet in cg_gcc~~ fixed that one.)

`@antoyo` please review the cg_gcc changes.
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@bors
bors committed Feb 24, 2022
2 parents 7ccfe2f + 96cf799 commit 3d127e2
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Showing 6 changed files with 158 additions and 150 deletions.
35 changes: 19 additions & 16 deletions compiler/rustc_codegen_gcc/src/builder.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -390,11 +390,6 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
bx
}

fn build_sibling_block(&mut self, name: &str) -> Self {
let block = self.append_sibling_block(name);
Self::build(self.cx, block)
}

fn llbb(&self) -> Block<'gcc> {
self.block.expect("block")
}
Expand All @@ -409,6 +404,11 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
func.new_block(name)
}

fn switch_to_block(&mut self, block: Self::BasicBlock) {
*self.cx.current_block.borrow_mut() = Some(block);
self.block = Some(block);
}

fn ret_void(&mut self) {
self.llbb().end_with_void_return(None)
}
Expand Down Expand Up @@ -880,28 +880,31 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
let start = dest.project_index(&mut self, zero).llval;
let end = dest.project_index(&mut self, count).llval;

let mut header_bx = self.build_sibling_block("repeat_loop_header");
let mut body_bx = self.build_sibling_block("repeat_loop_body");
let next_bx = self.build_sibling_block("repeat_loop_next");
let header_bb = self.append_sibling_block("repeat_loop_header");
let body_bb = self.append_sibling_block("repeat_loop_body");
let next_bb = self.append_sibling_block("repeat_loop_next");

let ptr_type = start.get_type();
let current = self.llbb().get_function().new_local(None, ptr_type, "loop_var");
let current_val = current.to_rvalue();
self.assign(current, start);

self.br(header_bx.llbb());
self.br(header_bb);

let keep_going = header_bx.icmp(IntPredicate::IntNE, current_val, end);
header_bx.cond_br(keep_going, body_bx.llbb(), next_bx.llbb());
self.switch_to_block(header_bb);
let keep_going = self.icmp(IntPredicate::IntNE, current_val, end);
self.cond_br(keep_going, body_bb, next_bb);

self.switch_to_block(body_bb);
let align = dest.align.restrict_for_offset(dest.layout.field(self.cx(), 0).size);
cg_elem.val.store(&mut body_bx, PlaceRef::new_sized_aligned(current_val, cg_elem.layout, align));
cg_elem.val.store(&mut self, PlaceRef::new_sized_aligned(current_val, cg_elem.layout, align));

let next = body_bx.inbounds_gep(self.backend_type(cg_elem.layout), current.to_rvalue(), &[self.const_usize(1)]);
body_bx.llbb().add_assignment(None, current, next);
body_bx.br(header_bx.llbb());
let next = self.inbounds_gep(self.backend_type(cg_elem.layout), current.to_rvalue(), &[self.const_usize(1)]);
self.llbb().add_assignment(None, current, next);
self.br(header_bb);

next_bx
self.switch_to_block(next_bb);
self
}

fn range_metadata(&mut self, _load: RValue<'gcc>, _range: WrappingRange) {
Expand Down
24 changes: 13 additions & 11 deletions compiler/rustc_codegen_llvm/src/builder.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -166,9 +166,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
Self::append_block(self.cx, self.llfn(), name)
}

fn build_sibling_block(&mut self, name: &str) -> Self {
let llbb = self.append_sibling_block(name);
Self::build(self.cx, llbb)
fn switch_to_block(&mut self, llbb: Self::BasicBlock) {
*self = Self::build(self.cx, llbb)
}

fn ret_void(&mut self) {
Expand Down Expand Up @@ -544,16 +543,19 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
let start = dest.project_index(&mut self, zero).llval;
let end = dest.project_index(&mut self, count).llval;

let mut header_bx = self.build_sibling_block("repeat_loop_header");
let mut body_bx = self.build_sibling_block("repeat_loop_body");
let next_bx = self.build_sibling_block("repeat_loop_next");
let header_bb = self.append_sibling_block("repeat_loop_header");
let body_bb = self.append_sibling_block("repeat_loop_body");
let next_bb = self.append_sibling_block("repeat_loop_next");

self.br(header_bx.llbb());
self.br(header_bb);

let mut header_bx = Self::build(self.cx, header_bb);
let current = header_bx.phi(self.val_ty(start), &[start], &[self.llbb()]);

let keep_going = header_bx.icmp(IntPredicate::IntNE, current, end);
header_bx.cond_br(keep_going, body_bx.llbb(), next_bx.llbb());
header_bx.cond_br(keep_going, body_bb, next_bb);

let mut body_bx = Self::build(self.cx, body_bb);
let align = dest.align.restrict_for_offset(dest.layout.field(self.cx(), 0).size);
cg_elem
.val
Expand All @@ -564,10 +566,10 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
current,
&[self.const_usize(1)],
);
body_bx.br(header_bx.llbb());
header_bx.add_incoming_to_phi(current, next, body_bx.llbb());
body_bx.br(header_bb);
header_bx.add_incoming_to_phi(current, next, body_bb);

next_bx
Self::build(self.cx, next_bb)
}

fn range_metadata(&mut self, load: &'ll Value, range: WrappingRange) {
Expand Down
112 changes: 58 additions & 54 deletions compiler/rustc_codegen_llvm/src/intrinsic.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -452,11 +452,11 @@ fn codegen_msvc_try<'ll>(
let (llty, llfn) = get_rust_try_fn(bx, &mut |mut bx| {
bx.set_personality_fn(bx.eh_personality());

let mut normal = bx.build_sibling_block("normal");
let mut catchswitch = bx.build_sibling_block("catchswitch");
let mut catchpad_rust = bx.build_sibling_block("catchpad_rust");
let mut catchpad_foreign = bx.build_sibling_block("catchpad_foreign");
let mut caught = bx.build_sibling_block("caught");
let normal = bx.append_sibling_block("normal");
let catchswitch = bx.append_sibling_block("catchswitch");
let catchpad_rust = bx.append_sibling_block("catchpad_rust");
let catchpad_foreign = bx.append_sibling_block("catchpad_foreign");
let caught = bx.append_sibling_block("caught");

let try_func = llvm::get_param(bx.llfn(), 0);
let data = llvm::get_param(bx.llfn(), 1);
Expand Down Expand Up @@ -520,12 +520,13 @@ fn codegen_msvc_try<'ll>(
let ptr_align = bx.tcx().data_layout.pointer_align.abi;
let slot = bx.alloca(bx.type_i8p(), ptr_align);
let try_func_ty = bx.type_func(&[bx.type_i8p()], bx.type_void());
bx.invoke(try_func_ty, try_func, &[data], normal.llbb(), catchswitch.llbb(), None);
bx.invoke(try_func_ty, try_func, &[data], normal, catchswitch, None);

normal.ret(bx.const_i32(0));
bx.switch_to_block(normal);
bx.ret(bx.const_i32(0));

let cs =
catchswitch.catch_switch(None, None, &[catchpad_rust.llbb(), catchpad_foreign.llbb()]);
bx.switch_to_block(catchswitch);
let cs = bx.catch_switch(None, None, &[catchpad_rust, catchpad_foreign]);

// We can't use the TypeDescriptor defined in libpanic_unwind because it
// might be in another DLL and the SEH encoding only supports specifying
Expand Down Expand Up @@ -558,21 +559,24 @@ fn codegen_msvc_try<'ll>(
// since our exception object effectively contains a Box.
//
// Source: MicrosoftCXXABI::getAddrOfCXXCatchHandlerType in clang
bx.switch_to_block(catchpad_rust);
let flags = bx.const_i32(8);
let funclet = catchpad_rust.catch_pad(cs, &[tydesc, flags, slot]);
let ptr = catchpad_rust.load(bx.type_i8p(), slot, ptr_align);
let funclet = bx.catch_pad(cs, &[tydesc, flags, slot]);
let ptr = bx.load(bx.type_i8p(), slot, ptr_align);
let catch_ty = bx.type_func(&[bx.type_i8p(), bx.type_i8p()], bx.type_void());
catchpad_rust.call(catch_ty, catch_func, &[data, ptr], Some(&funclet));
catchpad_rust.catch_ret(&funclet, caught.llbb());
bx.call(catch_ty, catch_func, &[data, ptr], Some(&funclet));
bx.catch_ret(&funclet, caught);

// The flag value of 64 indicates a "catch-all".
bx.switch_to_block(catchpad_foreign);
let flags = bx.const_i32(64);
let null = bx.const_null(bx.type_i8p());
let funclet = catchpad_foreign.catch_pad(cs, &[null, flags, null]);
catchpad_foreign.call(catch_ty, catch_func, &[data, null], Some(&funclet));
catchpad_foreign.catch_ret(&funclet, caught.llbb());
let funclet = bx.catch_pad(cs, &[null, flags, null]);
bx.call(catch_ty, catch_func, &[data, null], Some(&funclet));
bx.catch_ret(&funclet, caught);

caught.ret(bx.const_i32(1));
bx.switch_to_block(caught);
bx.ret(bx.const_i32(1));
});

// Note that no invoke is used here because by definition this function
Expand Down Expand Up @@ -613,30 +617,33 @@ fn codegen_gnu_try<'ll>(
// (%ptr, _) = landingpad
// call %catch_func(%data, %ptr)
// ret 1
let mut then = bx.build_sibling_block("then");
let mut catch = bx.build_sibling_block("catch");
let then = bx.append_sibling_block("then");
let catch = bx.append_sibling_block("catch");

let try_func = llvm::get_param(bx.llfn(), 0);
let data = llvm::get_param(bx.llfn(), 1);
let catch_func = llvm::get_param(bx.llfn(), 2);
let try_func_ty = bx.type_func(&[bx.type_i8p()], bx.type_void());
bx.invoke(try_func_ty, try_func, &[data], then.llbb(), catch.llbb(), None);
then.ret(bx.const_i32(0));
bx.invoke(try_func_ty, try_func, &[data], then, catch, None);

bx.switch_to_block(then);
bx.ret(bx.const_i32(0));

// Type indicator for the exception being thrown.
//
// The first value in this tuple is a pointer to the exception object
// being thrown. The second value is a "selector" indicating which of
// the landing pad clauses the exception's type had been matched to.
// rust_try ignores the selector.
bx.switch_to_block(catch);
let lpad_ty = bx.type_struct(&[bx.type_i8p(), bx.type_i32()], false);
let vals = catch.landing_pad(lpad_ty, bx.eh_personality(), 1);
let vals = bx.landing_pad(lpad_ty, bx.eh_personality(), 1);
let tydesc = bx.const_null(bx.type_i8p());
catch.add_clause(vals, tydesc);
let ptr = catch.extract_value(vals, 0);
bx.add_clause(vals, tydesc);
let ptr = bx.extract_value(vals, 0);
let catch_ty = bx.type_func(&[bx.type_i8p(), bx.type_i8p()], bx.type_void());
catch.call(catch_ty, catch_func, &[data, ptr], None);
catch.ret(bx.const_i32(1));
bx.call(catch_ty, catch_func, &[data, ptr], None);
bx.ret(bx.const_i32(1));
});

// Note that no invoke is used here because by definition this function
Expand Down Expand Up @@ -674,57 +681,54 @@ fn codegen_emcc_try<'ll>(
// %catch_data[1] = %is_rust_panic
// call %catch_func(%data, %catch_data)
// ret 1
let mut then = bx.build_sibling_block("then");
let mut catch = bx.build_sibling_block("catch");
let then = bx.append_sibling_block("then");
let catch = bx.append_sibling_block("catch");

let try_func = llvm::get_param(bx.llfn(), 0);
let data = llvm::get_param(bx.llfn(), 1);
let catch_func = llvm::get_param(bx.llfn(), 2);
let try_func_ty = bx.type_func(&[bx.type_i8p()], bx.type_void());
bx.invoke(try_func_ty, try_func, &[data], then.llbb(), catch.llbb(), None);
then.ret(bx.const_i32(0));
bx.invoke(try_func_ty, try_func, &[data], then, catch, None);

bx.switch_to_block(then);
bx.ret(bx.const_i32(0));

// Type indicator for the exception being thrown.
//
// The first value in this tuple is a pointer to the exception object
// being thrown. The second value is a "selector" indicating which of
// the landing pad clauses the exception's type had been matched to.
bx.switch_to_block(catch);
let tydesc = bx.eh_catch_typeinfo();
let lpad_ty = bx.type_struct(&[bx.type_i8p(), bx.type_i32()], false);
let vals = catch.landing_pad(lpad_ty, bx.eh_personality(), 2);
catch.add_clause(vals, tydesc);
catch.add_clause(vals, bx.const_null(bx.type_i8p()));
let ptr = catch.extract_value(vals, 0);
let selector = catch.extract_value(vals, 1);
let vals = bx.landing_pad(lpad_ty, bx.eh_personality(), 2);
bx.add_clause(vals, tydesc);
bx.add_clause(vals, bx.const_null(bx.type_i8p()));
let ptr = bx.extract_value(vals, 0);
let selector = bx.extract_value(vals, 1);

// Check if the typeid we got is the one for a Rust panic.
let rust_typeid = catch.call_intrinsic("llvm.eh.typeid.for", &[tydesc]);
let is_rust_panic = catch.icmp(IntPredicate::IntEQ, selector, rust_typeid);
let is_rust_panic = catch.zext(is_rust_panic, bx.type_bool());
let rust_typeid = bx.call_intrinsic("llvm.eh.typeid.for", &[tydesc]);
let is_rust_panic = bx.icmp(IntPredicate::IntEQ, selector, rust_typeid);
let is_rust_panic = bx.zext(is_rust_panic, bx.type_bool());

// We need to pass two values to catch_func (ptr and is_rust_panic), so
// create an alloca and pass a pointer to that.
let ptr_align = bx.tcx().data_layout.pointer_align.abi;
let i8_align = bx.tcx().data_layout.i8_align.abi;
let catch_data_type = bx.type_struct(&[bx.type_i8p(), bx.type_bool()], false);
let catch_data = catch.alloca(catch_data_type, ptr_align);
let catch_data_0 = catch.inbounds_gep(
catch_data_type,
catch_data,
&[bx.const_usize(0), bx.const_usize(0)],
);
catch.store(ptr, catch_data_0, ptr_align);
let catch_data_1 = catch.inbounds_gep(
catch_data_type,
catch_data,
&[bx.const_usize(0), bx.const_usize(1)],
);
catch.store(is_rust_panic, catch_data_1, i8_align);
let catch_data = catch.bitcast(catch_data, bx.type_i8p());
let catch_data = bx.alloca(catch_data_type, ptr_align);
let catch_data_0 =
bx.inbounds_gep(catch_data_type, catch_data, &[bx.const_usize(0), bx.const_usize(0)]);
bx.store(ptr, catch_data_0, ptr_align);
let catch_data_1 =
bx.inbounds_gep(catch_data_type, catch_data, &[bx.const_usize(0), bx.const_usize(1)]);
bx.store(is_rust_panic, catch_data_1, i8_align);
let catch_data = bx.bitcast(catch_data, bx.type_i8p());

let catch_ty = bx.type_func(&[bx.type_i8p(), bx.type_i8p()], bx.type_void());
catch.call(catch_ty, catch_func, &[data, catch_data], None);
catch.ret(bx.const_i32(1));
bx.call(catch_ty, catch_func, &[data, catch_data], None);
bx.ret(bx.const_i32(1));
});

// Note that no invoke is used here because by definition this function
Expand Down
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