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trans: report as many errors as possible for constants.
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@eddyb
eddyb committed Jun 5, 2016
1 parent d735f6b commit e71f6d8
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Showing 4 changed files with 107 additions and 41 deletions.
73 changes: 46 additions & 27 deletions src/librustc_trans/mir/block.rs
View file
Expand Up @@ -9,6 +9,7 @@
// except according to those terms.

use llvm::{self, ValueRef};
use rustc_const_eval::ErrKind;
use rustc::middle::lang_items;
use rustc::ty;
use rustc::mir::repr as mir;
Expand Down Expand Up @@ -222,41 +223,47 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
let const_cond = common::const_to_opt_uint(cond).map(|c| c == 1);

// Don't translate the panic block if success if known.
let lltarget = self.llblock(target);
if const_cond == Some(expected) {
funclet_br(bcx, lltarget);
funclet_br(self, bcx, target);
return;
}

if const_cond == Some(!expected) {
// Do nothing to end up with an unconditional panic.
// Pass the condition through llvm.expect for branch hinting.
let expect = bcx.ccx().get_intrinsic(&"llvm.expect.i1");
let cond = bcx.call(expect, &[cond, C_bool(bcx.ccx(), expected)], None);

// Create the failure block and the conditional branch to it.
let lltarget = llblock(self, target);
let panic_block = self.fcx.new_block("panic", None);
if expected {
bcx.cond_br(cond, lltarget, panic_block.llbb);
} else {
// Pass the condition through llvm.expect for branch hinting.
let expect = bcx.ccx().get_intrinsic(&"llvm.expect.i1");
let cond = bcx.call(expect, &[cond, C_bool(bcx.ccx(), expected)], None);

// Create the failure block and the conditional branch to it.
// After this point, bcx is the block for the call to panic.
let panic_block = self.fcx.new_block("panic", None);
if expected {
bcx.cond_br(cond, lltarget, panic_block.llbb);
} else {
bcx.cond_br(cond, panic_block.llbb, lltarget);
}
bcx = panic_block.build();
bcx.cond_br(cond, panic_block.llbb, lltarget);
}

// After this point, bcx is the block for the call to panic.
bcx = panic_block.build();

// Get the location information.
let loc = bcx.sess().codemap().lookup_char_pos(terminator.span.lo);
let filename = token::intern_and_get_ident(&loc.file.name);
let filename = C_str_slice(bcx.ccx(), filename);
let line = C_u32(bcx.ccx(), loc.line as u32);

// Put together the arguments to the panic entry point.
let (lang_item, args) = match *msg {
let (lang_item, args, const_err) = match *msg {
mir::AssertMessage::BoundsCheck { ref len, ref index } => {
let len = self.trans_operand(&mut bcx, len);
let index = self.trans_operand(&mut bcx, index);
let len = self.trans_operand(&mut bcx, len).immediate();
let index = self.trans_operand(&mut bcx, index).immediate();

let const_err = common::const_to_opt_uint(len).and_then(|len| {
common::const_to_opt_uint(index).map(|index| {
ErrKind::IndexOutOfBounds {
len: len,
index: index
}
})
});

let file_line = C_struct(bcx.ccx(), &[filename, line], false);
let align = llalign_of_min(bcx.ccx(), common::val_ty(file_line));
Expand All @@ -265,7 +272,8 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
align,
"panic_bounds_check_loc");
(lang_items::PanicBoundsCheckFnLangItem,
vec![file_line, index.immediate(), len.immediate()])
vec![file_line, index, len],
const_err)
}
mir::AssertMessage::Math(ref err) => {
let msg_str = token::intern_and_get_ident(err.description());
Expand All @@ -278,10 +286,23 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
msg_file_line,
align,
"panic_loc");
(lang_items::PanicFnLangItem, vec![msg_file_line])
(lang_items::PanicFnLangItem,
vec![msg_file_line],
Some(ErrKind::Math(err.clone())))
}
};

// If we know we always panic, and the error message
// is also constant, then we can produce a warning.
if const_cond == Some(!expected) {
if let Some(err) = const_err {
let _ = consts::const_err(bcx.ccx(),
terminator.span,
Err::<(), _>(err),
consts::TrueConst::No);
}
}

// Obtain the panic entry point.
let def_id = common::langcall(bcx.tcx(), Some(terminator.span), "", lang_item);
let callee = Callee::def(bcx.ccx(), def_id,
Expand All @@ -290,15 +311,13 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {

// Translate the actual panic invoke/call.
if let Some(unwind) = cleanup {
let uwbcx = self.bcx(unwind);
let unwind = self.make_landing_pad(uwbcx);
bcx.invoke(llfn,
&args,
self.unreachable_block().llbb,
unwind.llbb(),
cleanup_bundle.as_ref());
llblock(self, unwind),
cleanup_bundle);
} else {
bcx.call(llfn, &args, cleanup_bundle.as_ref());
bcx.call(llfn, &args, cleanup_bundle);
bcx.unreachable();
}
}
Expand Down
61 changes: 47 additions & 14 deletions src/librustc_trans/mir/constant.rs
View file
Expand Up @@ -270,15 +270,22 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
fn trans(&mut self) -> Result<Const<'tcx>, ConstEvalFailure> {
let tcx = self.ccx.tcx();
let mut bb = mir::START_BLOCK;

// Make sure to evaluate all statemenets to
// report as many errors as we possibly can.
let mut failure = Ok(());

loop {
let data = self.mir.basic_block_data(bb);
for statement in &data.statements {
match statement.kind {
mir::StatementKind::Assign(ref dest, ref rvalue) => {
let ty = self.mir.lvalue_ty(tcx, dest);
let ty = self.monomorphize(&ty).to_ty(tcx);
let value = self.const_rvalue(rvalue, ty, statement.span)?;
self.store(dest, value, statement.span);
match self.const_rvalue(rvalue, ty, statement.span) {
Ok(value) => self.store(dest, value, statement.span),
Err(err) => if failure.is_ok() { failure = Err(err); }
}
}
}
}
Expand All @@ -289,6 +296,7 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
mir::TerminatorKind::Drop { target, .. } | // No dropping.
mir::TerminatorKind::Goto { target } => target,
mir::TerminatorKind::Return => {
failure?;
return Ok(self.return_value.unwrap_or_else(|| {
span_bug!(span, "no returned value in constant");
}))
Expand All @@ -311,7 +319,10 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
ErrKind::Math(err.clone())
}
};
consts::const_err(self.ccx, span, Err(err), TrueConst::Yes)?;
match consts::const_err(self.ccx, span, Err(err), TrueConst::Yes) {
Ok(()) => {}
Err(err) => if failure.is_ok() { failure = Err(err); }
}
}
target
}
Expand All @@ -327,15 +338,21 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
func, fn_ty)
};

let args = args.iter().map(|arg| {
self.const_operand(arg, span)
}).collect::<Result<Vec<_>, _>>()?;
let value = MirConstContext::trans_def(self.ccx, instance, args)?;
let mut const_args = Vec::with_capacity(args.len());
for arg in args {
match self.const_operand(arg, span) {
Ok(arg) => const_args.push(arg),
Err(err) => if failure.is_ok() { failure = Err(err); }
}
}
if let Some((ref dest, target)) = *destination {
self.store(dest, value, span);
match MirConstContext::trans_def(self.ccx, instance, const_args) {
Ok(value) => self.store(dest, value, span),
Err(err) => if failure.is_ok() { failure = Err(err); }
}
target
} else {
span_bug!(span, "diverging {:?} in constant", terminator.kind)
span_bug!(span, "diverging {:?} in constant", terminator.kind);
}
}
_ => span_bug!(span, "{:?} in constant", terminator.kind)
Expand Down Expand Up @@ -425,8 +442,16 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
} else {
span_bug!(span, "index is not an integer-constant expression")
};
(Base::Value(const_get_elt(base.llval, &[iv as u32])),
ptr::null_mut())

// Produce an undef instead of a LLVM assertion on OOB.
let len = common::const_to_uint(tr_base.len(self.ccx));
let llelem = if iv < len {
const_get_elt(base.llval, &[iv as u32])
} else {
C_undef(type_of::type_of(self.ccx, projected_ty))
};

(Base::Value(llelem), ptr::null_mut())
}
_ => span_bug!(span, "{:?} in constant", projection.elem)
};
Expand Down Expand Up @@ -497,9 +522,17 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
}

mir::Rvalue::Aggregate(ref kind, ref operands) => {
let fields = operands.iter().map(|operand| {
Ok(self.const_operand(operand, span)?.llval)
}).collect::<Result<Vec<_>, _>>()?;
// Make sure to evaluate all operands to
// report as many errors as we possibly can.
let mut fields = Vec::with_capacity(operands.len());
let mut failure = Ok(());
for operand in operands {
match self.const_operand(operand, span) {
Ok(val) => fields.push(val.llval),
Err(err) => if failure.is_ok() { failure = Err(err); }
}
}
failure?;

// FIXME Shouldn't need to manually trigger closure instantiations.
if let mir::AggregateKind::Closure(def_id, substs) = *kind {
Expand Down
12 changes: 12 additions & 0 deletions src/librustc_trans/mir/rvalue.rs
View file
Expand Up @@ -27,6 +27,7 @@ use value::Value;
use Disr;

use super::MirContext;
use super::constant::const_scalar_checked_binop;
use super::operand::{OperandRef, OperandValue};
use super::lvalue::{LvalueRef, get_dataptr, get_meta};

Expand Down Expand Up @@ -588,6 +589,17 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
return OperandValue::Pair(val, C_bool(bcx.ccx(), false));
}

// First try performing the operation on constants, which
// will only succeed if both operands are constant.
// This is necessary to determine when an overflow Assert
// will always panic at runtime, and produce a warning.
match const_scalar_checked_binop(bcx.tcx(), op, lhs, rhs, input_ty) {
Some((val, of)) => {
return OperandValue::Pair(val, C_bool(bcx.ccx(), of));
}
None => {}
}

let (val, of) = match op {
// These are checked using intrinsics
mir::BinOp::Add | mir::BinOp::Sub | mir::BinOp::Mul => {
Expand Down
2 changes: 2 additions & 0 deletions src/test/compile-fail/const-err.rs
View file
Expand Up @@ -8,6 +8,8 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// compile-flags: -Zforce-overflow-checks=on

// these errors are not actually "const_err", they occur in trans/consts
// and are unconditional warnings that can't be denied or allowed

Expand Down

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