[Bug regression/39836] New: [4.4 regression] unoptimal code generated

["alexvod at google dot com" <gcc-bugzilla at gcc dot gnu dot org>]

Very simple code:

int* func();
int func2(long long);
void test (int unused, int idx, char tag, long long value)
{
  int *p = func() + idx;
  switch (tag) {
    case 1:
      *p = (int) value;
    case 2:
      *p = func2(value);
    }
}

is compiled to 46 bytes by GCC 4.3.1 and to 48 bytes by GCC 4.4.0. Bisection
shows that it was changed by
http://gcc.gnu.org/viewcvs?view=rev&revision=139949:

Code generated by 139948:
test:
        push    {r3, r4, r5, r6, r7, lr}
        mov     r4, r1
        mov     r5, r2
        ldr     r6, [sp, #24]
        ldr     r7, [sp, #28]
        bl      func
        lsl     r4, r4, #2
        add     r4, r0, r4
        cmp     r5, #1
        beq     .L3
        cmp     r5, #2
        bne     .L5
        b       .L4
.L3:
        str     r6, [r4]
.L4:
        mov     r0, r6
        mov     r1, r7
        bl      func2
        str     r0, [r4]
.L5:
        @ sp needed for prologue
        pop     {r3, r4, r5, r6, r7, pc}

Code generated by 139949:
test:
        push    {r4, r5, r6, r7, lr}
        sub     sp, sp, #12
        mov     r5, r1
        ldr     r1, [sp, #36]
        mov     r6, r2
        ldr     r7, [sp, #32]
        str     r1, [sp, #4]
        bl      func
        lsl     r4, r5, #2
        add     r4, r0, r4
        ldr     r1, [sp, #4]
        cmp     r6, #1
        beq     .L3
        cmp     r6, #2
        bne     .L5
        b       .L4
.L3:
        str     r7, [r4]
.L4:
        mov     r0, r7
        bl      func2
        str     r0, [r4]
.L5:
        add     sp, sp, #12
        @ sp needed for prologue
        pop     {r4, r5, r6, r7, pc}

Temporary variable was spilled on the stack [sp+4].

BTW, this function is compiled by GCC 4.2.1 to 42 (which is event better!).


-- 
           Summary: [4.4 regression] unoptimal code generated
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: regression
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: alexvod at google dot com
 GCC build triplet: x86_64-unknown-linux-gnu
  GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: arm-eabi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39836