[compiler-rt] support armv4t

[stuij]

Summary

The main thing that needed changing was excluding functionality that
isn't supported on armv4t. So excluding Arm specific builtin assembly files.

In the process some files were renamed and the source was annotated where
appropriate, so it's a bit easier to follow what group of files are meant for
what purpose.

[stuij]

fix renaming typo

[peter.smith]

Will take a look next week. I think you should be able to get v5t support from the same changes as the overall Arm/Thumb instruction. That could be done in a follow up patch though.

[peter.smith]

Code changes LGTM. I've made some suggestions for the comments and names.

compiler-rt/lib/builtins/CMakeLists.txt

378–380

IIUC these are the sources that can be used when either Arm state or Thumb2 is supported.

Would it be better to say:

# builtin support for Targets that have Arm state or have Thumb2 technology.
set(arm_or_thumb2_base_SOURCES
...

419–421

Suggest:
builtin support for Thumb-only targets without Thumb2 technology, such as v6-m and v8-m.baseline.

510

Suggest base functionality for Arm Targets prior to Arm v7-a and Armv6-m such as v6, v5t, v4t.

[stuij]

change wording/var as per review comments

[stuij]

compiler-rt/lib/builtins/CMakeLists.txt

419–421

I don't want to come across as too pedantic, but the Arm ARM actually states that v6-m and v8-m do include Thumb2, be it very minor. So I changed the wording slightly. I think/hope the updated wording captures that special class that v6-m and v8-m.baseline occupy.

[peter.smith]

Thanks for the updates LGTM too.

[MaskRay]

compiler-rt/lib/builtins/CMakeLists.txt

378–380

Targets => targets ?

compiler-rt/cmake/base-config-ix.cmake

elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "mips")
       else()
         test_target_arch(mips "" "-mips32r2" "-mabi=32" "-D_LARGEFILE_SOURCE" "-D_FILE_OFFSET_BITS=64")
         test_target_arch(mips64 "" "-mips64r2" "-mabi=64")
       endif()
     elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "arm")
       if(WIN32)
         test_target_arch(arm "" "" "")
       else()
+        test_target_arch(armv4t "" "-march=armv4t" "-mfloat-abi=soft")
+        test_target_arch(armv6m "" "-march=armv6m" "-mfloat-abi=soft")
         test_target_arch(arm "" "-march=armv7-a" "-mfloat-abi=soft")
         test_target_arch(armhf "" "-march=armv7-a" "-mfloat-abi=hard")
-        test_target_arch(armv6m "" "-march=armv6m" "-mfloat-abi=soft")
       endif()
     elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "avr")
       test_target_arch(avr "__AVR__" "--target=avr")
     elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "aarch32")
       test_target_arch(aarch32 "" "-march=armv8-a")
     elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "aarch64")
       test_target_arch(aarch64 "" "-march=armv8-a")
     elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "riscv32")

compiler-rt/cmake/builtin-config-ix.cmake

 
 builtin_check_c_compiler_source(COMPILER_RT_HAS_ASM_LSE
 "
 asm(\".arch armv8-a+lse\");
 asm(\"cas w0, w1, [x2]\");
 ")
 
 set(ARM64 aarch64)
-set(ARM32 arm armhf armv6m armv7m armv7em armv7 armv7s armv7k armv8m.main armv8.1m.main)
+set(ARM32 arm armhf armv4t armv6m armv7m armv7em armv7 armv7s armv7k armv8m.main armv8.1m.main)
 set(AVR avr)
 set(HEXAGON hexagon)
 set(X86 i386)
 set(X86_64 x86_64)
 set(LOONGARCH64 loongarch64)
 set(MIPS32 mips mipsel)
 set(MIPS64 mips64 mips64el)
 set(PPC32 powerpc powerpcspe)

compiler-rt/lib/builtins/CMakeLists.txt

set(x86_64_SOURCES
     ${GENERIC_SOURCES}
     ${x86_ARCH_SOURCES}
     x86_64/floatdidf.c
     x86_64/floatdisf.c
   )
   set(i386_SOURCES ${GENERIC_SOURCES} ${x86_ARCH_SOURCES})
 endif () # if (NOT MSVC)
 
-set(arm_SOURCES
+
+# builtin support for Targets that have Arm state or have Thumb2
+set(arm_or_thumb2_base_SOURCES
   arm/fp_mode.c
   arm/bswapdi2.S
   arm/bswapsi2.S
   arm/clzdi2.S
   arm/clzsi2.S
   arm/comparesf2.S
   arm/divmodsi4.S
   arm/divsi3.S
   arm/modsi3.S
+  arm/udivmodsi4.S
+  arm/udivsi3.S
+  arm/umodsi3.S
+  ${GENERIC_SOURCES}
+)
+
+set(arm_sync_SOURCES
   arm/sync_fetch_and_add_4.S
   arm/sync_fetch_and_add_8.S
   arm/sync_fetch_and_and_4.S
   arm/sync_fetch_and_and_8.S
   arm/sync_fetch_and_max_4.S
   arm/sync_fetch_and_max_8.S
   arm/sync_fetch_and_min_4.S
   arm/sync_fetch_and_min_8.S
   arm/sync_fetch_and_nand_4.S
   arm/sync_fetch_and_nand_8.S
   arm/sync_fetch_and_or_4.S
   arm/sync_fetch_and_or_8.S
   arm/sync_fetch_and_sub_4.S
   arm/sync_fetch_and_sub_8.S
   arm/sync_fetch_and_umax_4.S
   arm/sync_fetch_and_umax_8.S
   arm/sync_fetch_and_umin_4.S
   arm/sync_fetch_and_umin_8.S
   arm/sync_fetch_and_xor_4.S
   arm/sync_fetch_and_xor_8.S
-  arm/udivmodsi4.S
-  arm/udivsi3.S
-  arm/umodsi3.S
-  ${GENERIC_SOURCES}
 )
 
-set(thumb1_SOURCES
+# builtin support for Thumb-only targets with very limited Thumb2 technology,
+# such as v6-m and v8-m.baseline
+set(thumb1_base_SOURCES
   arm/divsi3.S
   arm/udivsi3.S
   arm/comparesf2.S
   arm/addsf3.S
   ${GENERIC_SOURCES}
 )
 
 set(arm_EABI_SOURCES
set(arm_Thumb1_VFPv2_SP_SOURCES
   arm/negsf2vfp.S
   arm/nesf2vfp.S
   arm/subsf3vfp.S
   arm/unordsf2vfp.S
 )
 set(arm_Thumb1_icache_SOURCES
   arm/sync_synchronize.S
 )
+
+# thumb1 calling into Arm to cover support
 set(arm_Thumb1_SOURCES
   ${arm_Thumb1_JT_SOURCES}
   ${arm_Thumb1_SjLj_EH_SOURCES}
   ${arm_Thumb1_VFPv2_DP_SOURCES}
   ${arm_Thumb1_VFPv2_SP_SOURCES}
   ${arm_Thumb1_icache_SOURCES}
 )
 
+# base functionality for Arm Targets prior to Arm v7-a and Armv6-m such as v6,
+# v5t, v4t
+set(arm_min_SOURCES
+  ${arm_or_thumb2_base_SOURCES}
+  ${arm_EABI_SOURCES}
+)
+
 if(MINGW)
   set(arm_SOURCES
     arm/aeabi_idivmod.S
     arm/aeabi_ldivmod.S
     arm/aeabi_uidivmod.S
     arm/aeabi_uldivmod.S
     arm/chkstk.S
-    ${arm_SOURCES}
+    ${arm_or_thumb2_base_SOURCES}
+    ${arm_sync_SOURCES}
+  )
+
+  set(thumb1_SOURCES
+    ${thumb1_base_SOURCES}
   )
 elseif(NOT WIN32)
   # TODO the EABI sources should only be added to EABI targets
   set(arm_SOURCES
-    ${arm_SOURCES}
+    ${arm_or_thumb2_base_SOURCES}
+    ${arm_sync_SOURCES}
     ${arm_EABI_SOURCES}
     ${arm_Thumb1_SOURCES}
   )
 
   set(thumb1_SOURCES
-    ${thumb1_SOURCES}
+    ${thumb1_base_SOURCES}
     ${arm_EABI_SOURCES}
   )
 endif()
 
 set(aarch64_SOURCES
   ${GENERIC_TF_SOURCES}
   ${GENERIC_SOURCES}
   cpu_model.c

 
 if (MINGW)
   set(aarch64_SOURCES
     ${aarch64_SOURCES}
     aarch64/chkstk.S
   )
 endif()
 
+set(armv4t_SOURCES ${arm_min_SOURCES})
 set(armhf_SOURCES ${arm_SOURCES})
 set(armv7_SOURCES ${arm_SOURCES})
 set(armv7s_SOURCES ${arm_SOURCES})
 set(armv7k_SOURCES ${arm_SOURCES})
 set(arm64_SOURCES ${aarch64_SOURCES})
 set(arm64e_SOURCES ${aarch64_SOURCES})
 set(arm64_32_SOURCES ${aarch64_SOURCES})