[LLVMbugs] [Bug 9970] New: A way to prevent the function-entry-time saving of registers

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Fri May 20 09:56:38 PDT 2011


           Summary: A way to prevent the function-entry-time saving of
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: ARM
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: xocotl at gmail.com
                CC: llvmbugs at cs.uiuc.edu

I have a function labelled __attribute__((noreturn)), essentially my main(), on
an ARM Thumb 2 where I have 256 bytes of stack. It doesn't generate a return,
but it would be nice if there were an attribute to also disable the
function-entry-time callee-saving of registers for noreturn functions.

Right now I get
   0:   e92d 48f0       stmdb   sp!, {r4, r5, r6, r7, fp, lr}
at the start, which is 24 bytes of stack down the drain, and when I put more
into the function it sometimes ends up 40 bytes.

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