[llvm-bugs] [Bug 50986] New: some ARM routines do not align sp to 8-byte boundaries

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https://bugs.llvm.org/show_bug.cgi?id=50986

            Bug ID: 50986
           Summary: some ARM routines do not align sp to 8-byte boundaries
           Product: compiler-rt
           Version: unspecified
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: compiler-rt
          Assignee: unassignedbugs at nondot.org
          Reporter: rin at NetBSD.org
                CC: llvm-bugs at lists.llvm.org

Created attachment 25001
  --> https://bugs.llvm.org/attachment.cgi?id=25001&action=edit
Fix stack alignment for ARM

For ARM EABI, stack pointer is required to be aligned to 8-byte boundaries.
However, unfortunately, some assembler routines in compiler-rt do not align sp
properly.

This is problematic especially for ARMv5TE; GCC emits {ld,st}rd for [sp, 8*x],
assuming that sp is properly aligned. If not, these instructions cause
alignment faults (operands for {ld,st}rd should be aligned to 8-byte boundaries
for pre-ARMv6 processors).

Please find the attached patch for fix against today's source at GitHub (by
Nick Hudson (skrll at NetBSD dot org) and myself):

(1) For aeabi_cfcmp.S, save ip additionally to ensure number of pushed
registers is even.

(2) For divmodsi4.S, divsi3.S, and modsi3.S, stop saving r7, which is not used
at the moment.

Thanks,
rin

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