[LLVMbugs] [Bug 7880] New: llc with frame pointer elimination disabled generates incorrect epilogue code for the ARM target

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=7880

           Summary: llc with frame pointer elimination disabled generates
                    incorrect epilogue code for the ARM target
           Product: libraries
           Version: 2.7
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: release blocker
          Priority: P
         Component: Backend: ARM
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: pawel at 32bitmicro.com
                CC: llvmbugs at cs.uiuc.edu


Using stock LVVM-2.7 x86_64  release
C file fbench.c is compiled to byte code - fbench.bc

/projects/test-suite/SingleSource/Benchmarks/Misc/fbench.c

llc is then used to produce assembly with the following options:

llc -O0 -regalloc=local -relocation-model=pic -f -disable-fp-elim fbench.bc -o
fbench.bc.s

fbench.bc.s is assembled and linked for Linux armel machine. Running the
executable results in segfault at the stack adjustment code in @ BB#13 shown
below: 

There seems to be two issues: 
- r11 (fp) does not have correct value for the stack pointer
- "sub" is generated instead of "add"

        sub    sp, r11, #28
    ldr    r4, [sp]


Larger fragment:

@ BB#13:
        ... -
    bl    printf(PLT)
    mov    r0, #0
    sub    sp, r11, #28
    ldr    r4, [sp]
    ldr    r5, [sp, #+4]
    ldr    r6, [sp, #+8]
    ldr    r7, [sp, #+12]
    ldr    r8, [sp, #+16]
    ldr    r9, [sp, #+20]
    ldr    r10, [sp, #+24]
    ldr    r11, [sp, #+28]
    ldr    lr, [sp, #+32]
    add    sp, sp, #36
    bx    lr
.LBB2_14:                               @ %bb29
    ldr    r0, .LCPI2_62
    ldr    r1, .LCPI2_63

-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.