[Bug middle-end/27226] Compiler looses track of alignment for emit_block_move

[amylaar at gcc dot gnu dot org]

------- Comment #3 from amylaar at gcc dot gnu dot org  2006-04-20 18:05 -------
(In reply to comment #2)
> You might want to dive into builtins.c:get_pointer_alignment.
> 

Hmm, indeed, I see that in 3.5.0 20040512, expand_builtin_memcpy
has found a dest_align of 32 and proceeded to go the store_by_pieces route.
The tree passed to get_poiter_alignment for the destination was:

 <nop_expr 0xb57cd794
    type <pointer_type 0xb58411b0
        type <integer_type 0xb58562f4 char QI
            size <integer_cst 0xb5854104 constant 8>
            unit size <integer_cst 0xb5854118 constant 1>
            align 8 symtab 0 alias set -1 precision 8 min <integer_cst
0xb58541a
4 -128> max <integer_cst 0xb58541b8 127>
            pointer_to_this <pointer_type 0xb58411b0>>
        unsigned SI
        size <integer_cst 0xb58547a8 constant 32>
        unit size <integer_cst 0xb58547d0 constant 4>
        align 32 symtab 0 alias set -1>

    arg 0 <plus_expr 0xb583e150
        type <pointer_type 0xb57ce438 type <array_type 0xb57ce0d8>
            unsigned SI size <integer_cst 0xb58547a8 32> unit size <integer_cst 
0xb58547d0 4>
            align 32 symtab 0 alias set -1>

        arg 0 <nop_expr 0xb57cd780 type <pointer_type 0xb57ce438>

            arg 0 <addr_expr 0xb57cd730 type <pointer_type 0xb57ce4a4>
                arg 0 <var_decl 0xb57ce288 s>>>
        arg 1 <integer_cst 0xb57cd76c constant 4>>>

In mainline, the calculated dest_align is 8.  The tree passed to
get_pointer_alignment is:

 <addr_expr 0xb58b13e0
    type <pointer_type 0xb58c6170
        type <integer_type 0xb58bd170 char sizes-gimplified public string-flag
QI
            size <integer_cst 0xb58ac1c8 constant invariant 8>
            unit size <integer_cst 0xb58ac1e0 constant invariant 1>
            align 8 symtab 0 alias set -1 precision 8 min <integer_cst
0xb58ac228 -128> max <integer_cst 0xb58ac288 127>
            pointer_to_this <pointer_type 0xb58c6170>>
        unsigned SI
        size <integer_cst 0xb58ac3c0 constant invariant 32>
        unit size <integer_cst 0xb58ac150 constant invariant 4>
        align 32 symtab 0 alias set -1>
    invariant
    arg 0 <array_ref 0xb593a820 type <integer_type 0xb58bd170 char>

        arg 0 <component_ref 0xb58bb078 type <array_type 0xb5938730>
            arg 0 <var_decl 0xb58ba108 s> arg 1 <field_decl 0xb593878c str>>
        arg 1 <integer_cst 0xb58ac168 constant invariant 0> arg 2 <integer_cst
0xb58ac168 0> arg 3 <integer_cst 0xb58ac1e0 1>>>


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27226