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Codegen tweaks #103511

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merged 5 commits into from
Oct 25, 2022
Merged

Codegen tweaks #103511

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4e4092f
rustc_codegen_ssa: use more consistent naming.
nnethercote Oct 18, 2022
a5bd5da
Rename two `TerminatorCodegenHelper` methods.
nnethercote Oct 18, 2022
03f350f
Clarify some cleanup stuff.
nnethercote Oct 18, 2022
8c02f4d
Inline and remove `cast_shift_rhs`.
nnethercote Oct 25, 2022
6cd35ac
Simplify `cast_shift_expr_rhs`.
nnethercote Oct 25, 2022
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46 changes: 16 additions & 30 deletions compiler/rustc_codegen_ssa/src/base.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -337,40 +337,26 @@ pub fn coerce_unsized_into<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(

pub fn cast_shift_expr_rhs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
bx: &mut Bx,
op: hir::BinOpKind,
lhs: Bx::Value,
rhs: Bx::Value,
) -> Bx::Value {
cast_shift_rhs(bx, op, lhs, rhs)
}

fn cast_shift_rhs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
bx: &mut Bx,
op: hir::BinOpKind,
lhs: Bx::Value,
rhs: Bx::Value,
) -> Bx::Value {
// Shifts may have any size int on the rhs
if op.is_shift() {
let mut rhs_llty = bx.cx().val_ty(rhs);
let mut lhs_llty = bx.cx().val_ty(lhs);
if bx.cx().type_kind(rhs_llty) == TypeKind::Vector {
rhs_llty = bx.cx().element_type(rhs_llty)
}
if bx.cx().type_kind(lhs_llty) == TypeKind::Vector {
lhs_llty = bx.cx().element_type(lhs_llty)
}
let rhs_sz = bx.cx().int_width(rhs_llty);
let lhs_sz = bx.cx().int_width(lhs_llty);
if lhs_sz < rhs_sz {
bx.trunc(rhs, lhs_llty)
} else if lhs_sz > rhs_sz {
// FIXME (#1877: If in the future shifting by negative
// values is no longer undefined then this is wrong.
bx.zext(rhs, lhs_llty)
} else {
rhs
}
let mut rhs_llty = bx.cx().val_ty(rhs);
let mut lhs_llty = bx.cx().val_ty(lhs);
if bx.cx().type_kind(rhs_llty) == TypeKind::Vector {
rhs_llty = bx.cx().element_type(rhs_llty)
}
if bx.cx().type_kind(lhs_llty) == TypeKind::Vector {
lhs_llty = bx.cx().element_type(lhs_llty)
}
let rhs_sz = bx.cx().int_width(rhs_llty);
let lhs_sz = bx.cx().int_width(lhs_llty);
if lhs_sz < rhs_sz {
bx.trunc(rhs, lhs_llty)
} else if lhs_sz > rhs_sz {
// FIXME (#1877: If in the future shifting by negative
// values is no longer undefined then this is wrong.
bx.zext(rhs, lhs_llty)
} else {
rhs
}
Expand Down
5 changes: 2 additions & 3 deletions compiler/rustc_codegen_ssa/src/common.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
#![allow(non_camel_case_types)]

use rustc_errors::struct_span_err;
use rustc_hir as hir;
use rustc_hir::LangItem;
use rustc_middle::mir::interpret::ConstValue;
use rustc_middle::ty::{self, layout::TyAndLayout, Ty, TyCtxt};
Expand Down Expand Up @@ -140,7 +139,7 @@ pub fn build_unchecked_lshift<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
lhs: Bx::Value,
rhs: Bx::Value,
) -> Bx::Value {
let rhs = base::cast_shift_expr_rhs(bx, hir::BinOpKind::Shl, lhs, rhs);
let rhs = base::cast_shift_expr_rhs(bx, lhs, rhs);
// #1877, #10183: Ensure that input is always valid
let rhs = shift_mask_rhs(bx, rhs);
bx.shl(lhs, rhs)
Expand All @@ -152,7 +151,7 @@ pub fn build_unchecked_rshift<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
lhs: Bx::Value,
rhs: Bx::Value,
) -> Bx::Value {
let rhs = base::cast_shift_expr_rhs(bx, hir::BinOpKind::Shr, lhs, rhs);
let rhs = base::cast_shift_expr_rhs(bx, lhs, rhs);
// #1877, #10183: Ensure that input is always valid
let rhs = shift_mask_rhs(bx, rhs);
let is_signed = lhs_t.is_signed();
Expand Down
86 changes: 47 additions & 39 deletions compiler/rustc_codegen_ssa/src/mir/block.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,9 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
}
}

fn lltarget<Bx: BuilderMethods<'a, 'tcx>>(
/// Get a basic block (creating it if necessary), possibly with a landing
/// pad next to it.
fn llbb_with_landing_pad<Bx: BuilderMethods<'a, 'tcx>>(
&self,
fx: &mut FunctionCx<'a, 'tcx, Bx>,
target: mir::BasicBlock,
Expand All @@ -73,32 +75,36 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
let target_funclet = fx.cleanup_kinds[target].funclet_bb(target);
match (self.funclet_bb, target_funclet) {
(None, None) => (lltarget, false),
(Some(f), Some(t_f)) if f == t_f || !base::wants_msvc_seh(fx.cx.tcx().sess) => {
(lltarget, false)
}
// jump *into* cleanup - need a landing pad if GNU, cleanup pad if MSVC
(None, Some(_)) => (fx.landing_pad_for(target), false),
(Some(_), None) => span_bug!(span, "{:?} - jump out of cleanup?", self.terminator),
(Some(_), Some(_)) => (fx.landing_pad_for(target), true),
(Some(f), Some(t_f)) => {
if f == t_f || !base::wants_msvc_seh(fx.cx.tcx().sess) {
(lltarget, false)
} else {
(fx.landing_pad_for(target), true)
}
}
}
}

/// Create a basic block.
fn llblock<Bx: BuilderMethods<'a, 'tcx>>(
/// Get a basic block (creating it if necessary), possibly with cleanup
/// stuff in it or next to it.
fn llbb_with_cleanup<Bx: BuilderMethods<'a, 'tcx>>(
&self,
fx: &mut FunctionCx<'a, 'tcx, Bx>,
target: mir::BasicBlock,
) -> Bx::BasicBlock {
let (lltarget, is_cleanupret) = self.lltarget(fx, target);
let (lltarget, is_cleanupret) = self.llbb_with_landing_pad(fx, target);
if is_cleanupret {
// MSVC cross-funclet jump - need a trampoline

debug!("llblock: creating cleanup trampoline for {:?}", target);
debug_assert!(base::wants_msvc_seh(fx.cx.tcx().sess));
debug!("llbb_with_cleanup: creating cleanup trampoline for {:?}", target);
let name = &format!("{:?}_cleanup_trampoline_{:?}", self.bb, target);
let trampoline = Bx::append_block(fx.cx, fx.llfn, name);
let mut trampoline_bx = Bx::build(fx.cx, trampoline);
let trampoline_llbb = Bx::append_block(fx.cx, fx.llfn, name);
let mut trampoline_bx = Bx::build(fx.cx, trampoline_llbb);
trampoline_bx.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
trampoline
trampoline_llbb
} else {
lltarget
}
Expand All @@ -110,10 +116,11 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
bx: &mut Bx,
target: mir::BasicBlock,
) {
let (lltarget, is_cleanupret) = self.lltarget(fx, target);
let (lltarget, is_cleanupret) = self.llbb_with_landing_pad(fx, target);
if is_cleanupret {
// micro-optimization: generate a `ret` rather than a jump
// MSVC micro-optimization: generate a `ret` rather than a jump
// to a trampoline.
debug_assert!(base::wants_msvc_seh(fx.cx.tcx().sess));
bx.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
} else {
bx.br(lltarget);
Expand All @@ -138,7 +145,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
let fn_ty = bx.fn_decl_backend_type(&fn_abi);

let unwind_block = if let Some(cleanup) = cleanup.filter(|_| fn_abi.can_unwind) {
Some(self.llblock(fx, cleanup))
Some(self.llbb_with_cleanup(fx, cleanup))
} else if fx.mir[self.bb].is_cleanup
&& fn_abi.can_unwind
&& !base::wants_msvc_seh(fx.cx.tcx().sess)
Expand Down Expand Up @@ -231,7 +238,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
options,
line_spans,
instance,
Some((ret_llbb, self.llblock(fx, cleanup), self.funclet(fx))),
Some((ret_llbb, self.llbb_with_cleanup(fx, cleanup), self.funclet(fx))),
);
} else {
bx.codegen_inline_asm(template, &operands, options, line_spans, instance, None);
Expand Down Expand Up @@ -281,8 +288,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
if target_iter.len() == 1 {
// If there are two targets (one conditional, one fallback), emit br instead of switch
let (test_value, target) = target_iter.next().unwrap();
let lltrue = helper.llblock(self, target);
let llfalse = helper.llblock(self, targets.otherwise());
let lltrue = helper.llbb_with_cleanup(self, target);
let llfalse = helper.llbb_with_cleanup(self, targets.otherwise());
if switch_ty == bx.tcx().types.bool {
// Don't generate trivial icmps when switching on bool
match test_value {
Expand All @@ -299,8 +306,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
} else {
bx.switch(
discr.immediate(),
helper.llblock(self, targets.otherwise()),
target_iter.map(|(value, target)| (value, helper.llblock(self, target))),
helper.llbb_with_cleanup(self, targets.otherwise()),
target_iter.map(|(value, target)| (value, helper.llbb_with_cleanup(self, target))),
);
}
}
Expand Down Expand Up @@ -530,7 +537,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
let cond = bx.expect(cond, expected);

// Create the failure block and the conditional branch to it.
let lltarget = helper.llblock(self, target);
let lltarget = helper.llbb_with_cleanup(self, target);
let panic_block = bx.append_sibling_block("panic");
if expected {
bx.cond_br(cond, lltarget, panic_block);
Expand Down Expand Up @@ -1459,20 +1466,20 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
// bar();
// }
Some(&mir::TerminatorKind::Abort) => {
let cs_bb =
let cs_llbb =
Bx::append_block(self.cx, self.llfn, &format!("cs_funclet{:?}", bb));
let cp_bb =
let cp_llbb =
Bx::append_block(self.cx, self.llfn, &format!("cp_funclet{:?}", bb));
ret_llbb = cs_bb;
ret_llbb = cs_llbb;

let mut cs_bx = Bx::build(self.cx, cs_bb);
let cs = cs_bx.catch_switch(None, None, &[cp_bb]);
let mut cs_bx = Bx::build(self.cx, cs_llbb);
let cs = cs_bx.catch_switch(None, None, &[cp_llbb]);

// The "null" here is actually a RTTI type descriptor for the
// C++ personality function, but `catch (...)` has no type so
// it's null. The 64 here is actually a bitfield which
// represents that this is a catch-all block.
let mut cp_bx = Bx::build(self.cx, cp_bb);
let mut cp_bx = Bx::build(self.cx, cp_llbb);
let null = cp_bx.const_null(
cp_bx.type_i8p_ext(cp_bx.cx().data_layout().instruction_address_space),
);
Expand All @@ -1481,30 +1488,31 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
cp_bx.br(llbb);
}
_ => {
let cleanup_bb =
let cleanup_llbb =
Bx::append_block(self.cx, self.llfn, &format!("funclet_{:?}", bb));
ret_llbb = cleanup_bb;
let mut cleanup_bx = Bx::build(self.cx, cleanup_bb);
ret_llbb = cleanup_llbb;
let mut cleanup_bx = Bx::build(self.cx, cleanup_llbb);
funclet = cleanup_bx.cleanup_pad(None, &[]);
cleanup_bx.br(llbb);
}
}
self.funclets[bb] = Some(funclet);
ret_llbb
} else {
let bb = Bx::append_block(self.cx, self.llfn, "cleanup");
let mut bx = Bx::build(self.cx, bb);
let cleanup_llbb = Bx::append_block(self.cx, self.llfn, "cleanup");
let mut cleanup_bx = Bx::build(self.cx, cleanup_llbb);

let llpersonality = self.cx.eh_personality();
let llretty = self.landing_pad_type();
let lp = bx.cleanup_landing_pad(llretty, llpersonality);
let lp = cleanup_bx.cleanup_landing_pad(llretty, llpersonality);

let slot = self.get_personality_slot(&mut bx);
slot.storage_live(&mut bx);
Pair(bx.extract_value(lp, 0), bx.extract_value(lp, 1)).store(&mut bx, slot);
let slot = self.get_personality_slot(&mut cleanup_bx);
slot.storage_live(&mut cleanup_bx);
Pair(cleanup_bx.extract_value(lp, 0), cleanup_bx.extract_value(lp, 1))
.store(&mut cleanup_bx, slot);

bx.br(llbb);
bx.llbb()
cleanup_bx.br(llbb);
cleanup_llbb
}
}

Expand Down
20 changes: 10 additions & 10 deletions compiler/rustc_codegen_ssa/src/mir/mod.rs
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Expand Up @@ -148,10 +148,10 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
let debug_context = cx.create_function_debug_context(instance, &fn_abi, llfn, &mir);

let start_llbb = Bx::append_block(cx, llfn, "start");
let mut bx = Bx::build(cx, start_llbb);
let mut start_bx = Bx::build(cx, start_llbb);

if mir.basic_blocks.iter().any(|bb| bb.is_cleanup) {
bx.set_personality_fn(cx.eh_personality());
start_bx.set_personality_fn(cx.eh_personality());
}

let cleanup_kinds = analyze::cleanup_kinds(&mir);
Expand Down Expand Up @@ -180,7 +180,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
caller_location: None,
};

fx.per_local_var_debug_info = fx.compute_per_local_var_debug_info(&mut bx);
fx.per_local_var_debug_info = fx.compute_per_local_var_debug_info(&mut start_bx);

// Evaluate all required consts; codegen later assumes that CTFE will never fail.
let mut all_consts_ok = true;
Expand All @@ -206,29 +206,29 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(

// Allocate variable and temp allocas
fx.locals = {
let args = arg_local_refs(&mut bx, &mut fx, &memory_locals);
let args = arg_local_refs(&mut start_bx, &mut fx, &memory_locals);

let mut allocate_local = |local| {
let decl = &mir.local_decls[local];
let layout = bx.layout_of(fx.monomorphize(decl.ty));
let layout = start_bx.layout_of(fx.monomorphize(decl.ty));
assert!(!layout.ty.has_erasable_regions());

if local == mir::RETURN_PLACE && fx.fn_abi.ret.is_indirect() {
debug!("alloc: {:?} (return place) -> place", local);
let llretptr = bx.get_param(0);
let llretptr = start_bx.get_param(0);
return LocalRef::Place(PlaceRef::new_sized(llretptr, layout));
}

if memory_locals.contains(local) {
debug!("alloc: {:?} -> place", local);
if layout.is_unsized() {
LocalRef::UnsizedPlace(PlaceRef::alloca_unsized_indirect(&mut bx, layout))
LocalRef::UnsizedPlace(PlaceRef::alloca_unsized_indirect(&mut start_bx, layout))
} else {
LocalRef::Place(PlaceRef::alloca(&mut bx, layout))
LocalRef::Place(PlaceRef::alloca(&mut start_bx, layout))
}
} else {
debug!("alloc: {:?} -> operand", local);
LocalRef::new_operand(&mut bx, layout)
LocalRef::new_operand(&mut start_bx, layout)
}
};

Expand All @@ -240,7 +240,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
};

// Apply debuginfo to the newly allocated locals.
fx.debug_introduce_locals(&mut bx);
fx.debug_introduce_locals(&mut start_bx);

// Codegen the body of each block using reverse postorder
for (bb, _) in traversal::reverse_postorder(&mir) {
Expand Down