[compiler-rt] support armv4t

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.

Reviewed By: peter.smith, nickdesaulniers

Differential Revision: https://reviews.llvm.org/D138725

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

@@ -236,9 +236,10 @@ macro(test_targets)
       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")

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

@@ -45,7 +45,7 @@ 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)

compiler-rt/lib/builtins/CMakeLists.txt

@@ -375,7 +375,9 @@ else () # MSVC
   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
@@ -385,6 +387,13 @@ set(arm_SOURCES
   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
@@ -405,13 +414,11 @@ set(arm_SOURCES
   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
@@ -490,6 +497,8 @@ set(arm_Thumb1_VFPv2_SP_SOURCES
 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}
@@ -498,6 +507,13 @@ set(arm_Thumb1_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
@@ -505,18 +521,24 @@ if(MINGW)
     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()
@@ -563,6 +585,7 @@ if (MINGW)
   )
 endif()
 
+set(armv4t_SOURCES ${arm_min_SOURCES})
 set(armhf_SOURCES ${arm_SOURCES})
 set(armv7_SOURCES ${arm_SOURCES})
 set(armv7s_SOURCES ${arm_SOURCES})