[Bug target/56102] New: Wrong rtx cost calculated for Thumb1

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56102

             Bug #: 56102
           Summary: Wrong rtx cost calculated for Thumb1
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: amker.cheng@gmail.com


For below program:

double g = 1.0;
double func(int a, double d)
{
    if (a > 0)
    return 0.0 + g;
    else
    return 2.0 + d;
}

compiling with:
./arm-none-eabi-gcc -mthumb -mcpu=cortex-m0 -Os test.c -S -o test.S

The assembly code is:
    .cpu cortex-m0
    .fpu softvfp
    .eabi_attribute 20, 1
    .eabi_attribute 21, 1
    .eabi_attribute 23, 3
    .eabi_attribute 24, 1
    .eabi_attribute 25, 1
    .eabi_attribute 26, 1
    .eabi_attribute 30, 4
    .eabi_attribute 34, 0
    .eabi_attribute 18, 4
    .code    16
    .file    "main.c"
    .global    __aeabi_dadd
    .text
    .align    1
    .global    func
    .code    16
    .thumb_func
    .type    func, %function
func:
    push    {r3, lr}
    cmp    r0, #0
    ble    .L2
    ldr    r3, .L6+16
    ldr    r0, [r3]
    ldr    r1, [r3, #4]
    ldr    r3, .L6+4
    ldr    r2, .L6
    b    .L4
.L2:
    mov    r0, r2
    mov    r1, r3
    ldr    r2, .L6+8
    ldr    r3, .L6+12
.L4:
    bl    __aeabi_dadd
    @ sp needed
    pop    {r3, pc}
.L7:
    .align    3
.L6:
    .word    0
    .word    0
    .word    0
    .word    1073741824
    .word    .LANCHOR0
    .size    func, .-func
    .global    g
    .data
    .align    3
    .set    .LANCHOR0,. + 0
    .type    g, %object
    .size    g, 8
g:
    .word    0
    .word    1072693248
    .ident    "GCC: (GNU) 4.8.0 20130122 (experimental)"

The problem is double word constant isn't split by GCC, causing bigger code
size.