[PATCH] D27309: builtins: Add ARM Thumb1 implementation for uidiv and uidivmod

[Michal Meloun via Phabricator via llvm-commits]

strejda added a comment.

In https://reviews.llvm.org/D27309#698696, @weimingz wrote:

> Most of the changes are guarded by __ARM_ARCH_ISA_THUMB == 1 and I reviewed again of the "else" part and they look OK except for one suspect:
>  https://reviews.llvm.org/D30867


No, unfortunately, _ _ARM_ARCH_ISA_THUMB == n can't be used as selector for Thumb1 (or Thumb2) code. 
Value of  _ _ARM_ARCH_ISA_THUMB isn't based on actual compilation  mode (-mthumb, -marm), its based on given CPU (or arch) capabilities.
Thus, if we compile library with '-marm  -march=armv6' then _ _ARM_ARCH_ISA_THUMB is set to '1'. So we ends with Thumb1 code compiled using ARM ISA. Not a nice result, right?
So https://reviews.llvm.org/D30867 cannot help us.

I found these problems:

- Thumb[1][2] code selection is broken,   "(_ _ARM_ARCH_ISA_THUMB == n && (defined(_ _THUMBEL_ _) || defined(_ _THUMBEB_ _))" is right condition. See: https://github.com/strejda/tegra/commit/91057bb46e54e350da87e354aed3189d469da458#diff-a8e5a4d82eadfcc89b4f54d6755a46b4L97

  This one is fatal for FreeBSD.

- all Thumb1  and some Thumb2 functions are not properly decorated by DEFINE_COMPILERRT_THUMB_FUNCTION() This breaks debugging.

- usage of '.thumb' directive is inconsistent  across files

- Thumb 1 version of __udivsi3 is broken and doesn't not work at all. See:

  	cmp	r0, r1, lsl IMM shift
   	addhs	r3, r3, IMM (1 << shift)
   	subhs	r0, r0, r1, lsl IMM shift

  and

  	lsls	r2, r1, IMM shift
  	cmp	r0, r2
  	blo	1f
  	subs	r0, r0, r2
  1:
  	adcs	r3, r3



- There is no Thumb1 variant of __udivmodsi4


Repository:
  rL LLVM

https://reviews.llvm.org/D27309