[Bug c/17201] New: Incorrect code generated for logical shift

[Nigel dot Hathaway at arm dot com]

static int
ins_will_execute(unsigned long ins)
{
    unsigned long psr = get_register(PS);  // condition codes
    int res = 0;
    switch ((ins & 0xF0000000) >> 28) {

generates the following (as reported by gdb):

0x0000b1b8 <ins_will_execute>:     mov    r12, sp
0x0000b1bc <ins_will_execute+4>:   stmdb  sp!, {r11, r12, lr, pc}
0x0000b1c0 <ins_will_execute+8>:   sub    r11, r12, #4	; 0x4
0x0000b1c4 <ins_will_execute+12>:  sub    sp, sp, #20	; 0x14
0x0000b1c8 <ins_will_execute+16>:  str    r0, [r11, #-16]
    unsigned long psr = get_register(PS);  // condition codes
0x0000b1cc <ins_will_execute+20>:  ldr    r3, [pc, #808]	; 0xb4fc <$d>
0x0000b1d0 <ins_will_execute+24>:  ldr    r3, [r3]
0x0000b1d4 <ins_will_execute+28>:  ldr    r3, [r3, #64]
0x0000b1d8 <ins_will_execute+32>:  str    r3, [r11, #-20]
    int res = 0;
0x0000b1dc <ins_will_execute+36>:  mov    r3, #0	; 0x0
0x0000b1e0 <ins_will_execute+40>:  str    r3, [r11, #-24]
    switch ((ins & 0xF0000000) >> 28) {
0x0000b1e4 <ins_will_execute+44>:  ldr    r3, [r11, #-16]
0x0000b1e8 <ins_will_execute+48>:  and    r3, r3, #-268435456	; 0xf0000000
0x0000b1ec <ins_will_execute+52>:  mov    r3, r3, lsl #28
0x0000b1f0 <ins_will_execute+56>:  cmp    r3, #15	; 0xf
0x0000b1f4 <ins_will_execute+60>:  ldrls  pc, [pc, r3, lsl #2]
0x0000b1f8 <ins_will_execute+64>:  b      0xb4ec <$a+688>

Note <ins_will_execute+52>: the generated code is a shift left, whereas the 
source code is a shift right. [The code snippet is from eCos debug single step  
support.]

-- 
           Summary: Incorrect code generated for logical shift
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: Nigel dot Hathaway at arm dot com
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-cygwin
GCC target triplet: arm-elf-gcc


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17201