[Bug target/67317] [x86] Silly code generation for _addcarry_u32/_addcarry_u64

["ubizjak at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67317

Uroš Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |ubizjak at gmail dot com

--- Comment #6 from Uroš Bizjak <ubizjak at gmail dot com> ---
Created attachment 36258
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36258&action=edit
Proposed patch

This patch changes expanders of carry-handling builtins to use
addqi3_cconly_overflow and canonicalizes carry hanling insn to what combine can
process:

(define_insn "addcarry<mode>"
  [(set (reg:CCC FLAGS_REG)
        (compare:CCC
          (plus:SWI48
            (plus:SWI48
              (match_operator:SWI48 4 "ix86_carry_flag_operator"
               [(match_operand 3 "flags_reg_operand") (const_int 0)])
              (match_operand:SWI48 1 "nonimmediate_operand" "%0"))
            (match_operand:SWI48 2 "nonimmediate_operand" "rm"))
          (match_dup 1)))
   (set (match_operand:SWI48 0 "register_operand" "=r")
        (plus:SWI48 (plus:SWI48 (match_op_dup 4
                                 [(match_dup 3) (const_int 0)])
                                (match_dup 1))
                    (match_dup 2)))]
  "ix86_binary_operator_ok (PLUS, <MODE>mode, operands)"
  "adc{<imodesuffix>}\t{%2, %0|%0, %2}"
  [(set_attr "type" "alu")
   (set_attr "use_carry" "1")
   (set_attr "pent_pair" "pu")
   (set_attr "mode" "<MODE>")])

and

(define_insn "subborrow<mode>"
  [(set (reg:CCC FLAGS_REG)
        (compare:CCC
          (match_operand:SWI48 1 "nonimmediate_operand" "0")
          (plus:SWI48
            (match_operator:SWI48 4 "ix86_carry_flag_operator"
             [(match_operand 3 "flags_reg_operand") (const_int 0)])
            (match_operand:SWI48 2 "nonimmediate_operand" "rm"))))
   (set (match_operand:SWI48 0 "register_operand" "=r")
        (minus:SWI48 (minus:SWI48 (match_dup 1)
                                  (match_op_dup 4
                                   [(match_dup 3) (const_int 0)]))
                     (match_dup 2)))]
  "ix86_binary_operator_ok (MINUS, <MODE>mode, operands)"
  "sbb{<imodesuffix>}\t{%2, %0|%0, %2}"
  [(set_attr "type" "alu")
   (set_attr "use_carry" "1")
   (set_attr "pent_pair" "pu")
   (set_attr "mode" "<MODE>")])

The patch also rewrites expander to fix a bug, where carry-clobbering insns
were emitted inside carry-flag def-use chain.

For the testcase, patched gcc generates:

testcarry_u64:
        addq    %rdi, %rdx
        adcq    %rsi, %rcx
        movq    %rdx, %rax
        xorq    %rcx, %rax
        ret
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Subject: [Bug target/67317] [x86] Silly code generation for _addcarry_u32/_addcarry_u64
Date: Thu, 27 Aug 2015 09:03:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67317

Uroš Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|x86_64-*-*                  |x86
                 CC|uros at gcc dot gnu.org            |
   Target Milestone|---                         |5.3
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From: "rogero at howzatt dot demon.co.uk" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug lto/67357] -Wodr warnings from types in anonymous namespace
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg357

--- Comment #3 from Roger Orr <rogero at howzatt dot demon.co.uk> ---
The following code block also gives an ODR violation with the same versions of
gcc; in this case only a *single* translation unit is involved.

$ cat test.cxx
#include <memory>

template<typename T>
class D : public T {
    using mfn_t = void (D::*)();
    std::tuple<mfn_t> data{&D::foo};
public:
    void foo() {
        std::get<0>(data);
    }
};

namespace {
    struct S {};
}

int main() {
    D<S> obj;
}

$ /opt/gcc-5.2.0/bin/g++ -flto -Wodr -std=c++11 test.cxx
test.cxx:5:32: warning: type 'struct mfn_t' violates one definition rule
[-Wodr]
     using mfn_t = void (D::*)();
                                ^
/opt/gcc-5.2.0/include/c++/5.2.0/tuple:764:21: note: a different type is
defined in another translation unit
       typedef _Head type;
                     ^
test.cxx:5:32: note: the first difference of corresponding definitions is field
'__pfn'
     using mfn_t = void (D::*)();
                                ^
test.cxx:5:32: note: a field of same name but different type is defined in
another translation unit
lto1: note: type mismatch in parameter 1
test.cxx:4:20: note: type 'struct D' defined in anonymous namespace can not
match type 'struct D'
 class D : public T {
                    ^
test.cxx:4:7: note: the incompatible type defined in anonymous namespace in
another translation unit
 class D : public T {
       ^

(Giving the anonymous namespace a name removes the warnings.)