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digitalmars.D.bugs - [Issue 8796] New: Optimizer bug on 64bit

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8796

           Summary: Optimizer bug on 64bit
           Product: D
           Version: unspecified
          Platform: x86_64
        OS/Version: All
            Status: NEW
          Severity: critical
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: dmitry.olsh gmail.com



14:13:18 PDT ---
Uncovered while doing a re-write for std.array.insertInPlace.
It got caught by pull auto-tester.

Sample:

import std.conv, std.utf;

void insertInPlace(T, U...)(ref T[] array, size_t pos, U stuff)
{
    {// mutable, can do in place
        //helper function: re-encode dchar to Ts and store at *ptr
        static T* putDChar(T* ptr, dchar ch)
        {
            static if(is(T == dchar))
            {
                *ptr++ = ch;
                return ptr;
            }
            else
            {
                T[dchar.sizeof/T.sizeof] buf;
                size_t len = encode(buf, ch);
                final switch(len)
                {
                static if(T.sizeof == char.sizeof)
                {
                case 4:
                    ptr[3] = buf[3];
                    goto case;
                case 3:
                    ptr[2] = buf[2];
                    goto case;
                }
                case 2:
                    ptr[1] = buf[1];
                    goto case;
                case 1:
                    ptr[0] = buf[0];
                }
                ptr += len;
                return ptr;
            }
        }

        immutable oldLen = array.length;
        size_t to_insert = 0;

        foreach (i, E; U)
            to_insert += codeLength!T(stuff[i]);
        array.length += to_insert;

        auto ptr = array.ptr + pos;
        foreach (i, E; U)
        {
            static if(is(E : dchar))
            {                
                ptr = putDChar(ptr, stuff[i]);
            }
            else
            {
                foreach (dchar ch; stuff[i])
                    ptr = putDChar(ptr, ch);
            }
        }
        assert(ptr == array.ptr + pos + to_insert, text(ptr - array.ptr, " vs
",pos+ to_insert ));
    }
}

void main()
{
    auto l = "hello"d.dup;
    auto r = " વિશ્વ".dup;
    l.insertInPlace(0, r);                
}


Compiled as 
dmd -O atest.d

It fails with:
core.exception.AssertError atest.d(75): 0 vs 6

Compiled without -O it doesn't fail. It also works fine in 32 bits.
Tested with dmd 2.061 from github. Commit
a1287bd0b1931917f4e43b5e2d7b997f0d60adf6.

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next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8796


Don <clugdbug yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Optimizer bug on 64bit      |Optimizer bug on 64bit:
                   |                            |*p++=1 where p is a
                   |                            |parameter



Reduced test case (applies to postfix ++ and --):

int* wrong8796(int* p)
{
    *p++ = 1;
    return p;
}

// The wrong code is generated in the function above, main() is just to
demonstrate

void main()
{
    int [3] arr;
    int * q = arr.ptr;
    q = wrong8796(q);
    assert(q != arr.ptr);
}

Without -O, wrong8796() compiles to:

        push    RBP
        mov    RBP,RSP
        sub    RSP,8
        mov    -8[RBP],RDI
        mov    RAX,-8[RBP]
        add    qword ptr -8[RBP],4
        mov    dword ptr [RAX],1
        mov    RAX,-8[RBP]
        leave
        ret

With -O:

        push    RBP
        mov    RBP,RSP
        mov    RAX,RDI
        mov    qword ptr [RAX],1
        add    RAX,4
        mov    RAX,RDI                <---- wrong
        pop    RBP
        ret

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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Commit pushed to dmd-1.x at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/5b7620ea1c664ac7686070a8493edcd34d9929fc
fix Issue 8796 - Optimizer bug on 64bit: *p++=1 where p is a parameter

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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Commit pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/de67647952432b11e61d7f79129a4f9d7f00e37a
fix Issue 8796 - Optimizer bug on 64bit: *p++=1 where p is a parameter

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prev sibling parent d-bugmail puremagic.com writes:
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Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla digitalmars.com
           Platform|x86_64                      |All
            Version|D2                          |D1 & D2
         Resolution|                            |FIXED



23:58:07 PST ---
This bug has lurked for a very long time, and was on all platforms.

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