https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79958
Bug ID: 79958
Summary: Missed tree DSE
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jakub at gcc dot gnu.org
Target Milestone: ---
At -O3 in bar we have various dead temporaries, they don't have address taken
and so should be DSEd, but they aren't. In foo which doesn't have the EH edges
this works well.
#include <cstddef>
#include <functional>
#include <stdint.h>
namespace
{
struct bitarray
{
bitarray(int i) : mSlice(i) {}
template<typename EXPR>
bitarray(const EXPR &expr) { mSlice = expr.slice(0); }
uint32_t
slice(ptrdiff_t index) const { if (index != 0) return 0; return mSlice; }
private:
uint32_t mSlice;
};
template<typename LEFT, typename RIGHT, template<typename T> class OP>
struct bit_binary_expr
{
bit_binary_expr(const LEFT &left, const RIGHT &right) : mLeft(left),
mRight(right) {}
uint32_t slice(ptrdiff_t index) const { OP<uint32_t> op; return
op(mLeft.slice(index), mRight.slice(index)); }
private:
const LEFT &mLeft;
const RIGHT &mRight;
};
template<typename LEFT, typename RIGHT>
bit_binary_expr<LEFT, RIGHT, ::std::bit_and>
operator &(const LEFT &left, const RIGHT &right) { return
bit_binary_expr<LEFT, RIGHT, ::std::bit_and>(left, right); }
template<typename LEFT, typename RIGHT>
bit_binary_expr<LEFT, RIGHT, ::std::bit_or> operator |(const LEFT &left,
const RIGHT &right)
{ return bit_binary_expr<LEFT, RIGHT, ::std::bit_or>(left, right); }
template<typename OPERAND>
struct bit_shift_left
{
bit_shift_left(const OPERAND &operand, size_t nBits) : mOperand(operand),
mBits(nBits) {}
uint32_t slice(ptrdiff_t index) const
{
const ptrdiff_t offset = mBits / 32;
const size_t bits = mBits % 32;
if (bits == 0)
return mOperand.slice(index - offset);
else
return (mOperand.slice(index - offset) << bits) | (mOperand.slice(index
- offset - 1) >> (32 - bits));
}
private:
const OPERAND &mOperand;
const size_t mBits;
};
template<typename OPERAND>
bit_shift_left<OPERAND> operator <<(const OPERAND &operand, size_t nBits) {
return bit_shift_left<OPERAND>(operand, nBits); }
}
struct Foo
{
void write(const bitarray &);
};
void
foo(int i)
{
Foo f;
f.write(bitarray(( ((((bitarray(i) & bitarray(0x00000001))) << 31) |
bitarray(0x40000000)))
| ((((bitarray(42) & bitarray(0x0000ffff))) << 8) |
bitarray(0x00000080))));
}
struct Bar
{
~Bar(void);
void write(const bitarray &) /* throw() */;
};
void
bar(int i)
{
Bar b;
b.write(bitarray(( ((((bitarray(i) & bitarray(0x00000001))) << 31) |
bitarray(0x40000000)))
| ((((bitarray(42) & bitarray(0x0000ffff))) << 8) |
bitarray(0x00000080))));
}
