[Bug target/43546] [4.4/4.5 Regression] ICE: in assign_stack_local_1, at function.c:353 with -mpreferred-stack-boundary=2 -msseregparm

[rguenth at gcc dot gnu dot org]

------- Comment #8 from rguenth at gcc dot gnu dot org  2010-03-27 16:38 -------
Just to clarify, the issue is that

(insn 6 5 7 2 t.i:2 (set (reg:DF 21 xmm0)
        (float_extend:DF (mem/u/c/i:SF (symbol_ref/u:SI ("*.LC0") [flags 0x2])
[0 S4 A32]))) 99 {*extendsfdf2_i387} (expr_list:REG_EQUAL (const_double:DF
-2147483648 [0x80000000] 1.0e+0 [0x0.8p+1])
        (nil)))

with

(define_insn "*extendsfdf2_i387"
  [(set (match_operand:DF 0 "nonimmediate_operand" "=f,m")
        (float_extend:DF (match_operand:SF 1 "nonimmediate_operand" "fm,f")))]
  "TARGET_80387"
  "* return output_387_reg_move (insn, operands);"
  [(set_attr "type" "fmov")
   (set_attr "mode" "SF,XF")])

requires a reload for the x87 register to xmm0 move.  The

(define_insn "*extendsfdf2_sse"
  [(set (match_operand:DF 0 "nonimmediate_operand" "=x")
        (float_extend:DF (match_operand:SF 1 "nonimmediate_operand" "xm")))]
  "TARGET_SSE2 && TARGET_SSE_MATH"
  "%vcvtss2sd\t{%1, %d0|%d0, %1}"
  [(set_attr "type" "ssecvt")
   (set_attr "prefix" "maybe_vex")
   (set_attr "mode" "DF")])

alternative is not enabled, both because just -msse is supplied and
SSE math is not enabled.  But I fail to see why we can't go through
unaligned memory if the user asks us to - which puts the finger
at the assert that triggers (and maybe reload if it can not properly
deal with less aligned stack slots).

Testcase that doesn't need -msseregparm:

extern void __attribute__((sseregparm)) bar(double);
void foo() { bar(1.0); }

commenting the assert yields odd

foo:
        pushl   %ebp
        movl    %esp, %ebp
        subl    $8, %esp
        fld1
        fstpl   -8(%ebp)
        movlps  -8(%ebp), %xmm0
        call    bar
        leave
        ret

obviously w/o -msse2 there's no movsd, thus the odd code.

And the handed out secondary memory has correct alignment:

insn 6 5 11 2 t.i:2 (set (reg:DF 8 st)
        (float_extend:DF (mem/u/c/i:SF (symbol_ref/u:SI ("*.LC0") [flags 0x2])
[0 S4 A32]))) 99 {*extendsfdf2_i387} (expr_list:REG_EQUAL (const_double:DF
-2147483648 [0x80000000] 1.0e+0 [0x0.8p+1])
        (nil)))

(insn 11 6 12 2 t.i:2 (set (mem/c:DF (plus:SI (reg/f:SI 6 bp)
                (const_int -8 [0xfffffff8])) [0 S8 A32])
        (reg:DF 8 st)) 74 {*movdf_nointeger} (nil))

(insn 12 11 7 2 t.i:2 (set (reg:DF 21 xmm0)
        (mem/c:DF (plus:SI (reg/f:SI 6 bp)
                (const_int -8 [0xfffffff8])) [0 S8 A32])) 74 {*movdf_nointeger}
(nil))

(call_insn 7 12 10 2 t.i:2 (call (mem:QI (symbol_ref:SI ("bar") [flags 0x41] 
<function_decl 0xb77a4c80 bar>) [0 S1 A8])
        (const_int 0 [0x0])) 484 {*call_0} (nil)
    (expr_list:REG_DEP_TRUE (use (reg:DF 21 xmm0))
        (nil)))

so why are we using assign_stack_local here and not assign_stack_local_1 (...,
true)?  Here, at

#3  0x0846d729 in get_secondary_mem (x=0xb77a96f0, mode=DFmode, opnum=0, 
    type=RELOAD_FOR_OUTPUT) at /home/richard/src/trunk/gcc/reload.c:608
608             = assign_stack_local (mode, GET_MODE_SIZE (mode), 0);
(gdb) l
603         {
604     #ifdef SECONDARY_MEMORY_NEEDED_RTX
605           secondary_memlocs[(int) mode] = SECONDARY_MEMORY_NEEDED_RTX
(mode);
606     #else
607           secondary_memlocs[(int) mode]
608             = assign_stack_local (mode, GET_MODE_SIZE (mode), 0);
609     #endif
610         }


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43546