[builtins] ARM: Reland fix for assembling builtins in thumb state.

[manojgupta]

Summary

clang does not assemble files in thumb mode unless .thumb declaration
is present. Add .thumb/.arm decl to _FUNCTION macros to ensure that
files are assembled correctly.

Also add a fix to ensure that armv7k-watchos can assemble the
aeabi_c{f|d}cmp.S files.

Fixes PR 34715.

[peter.smith]

I've made one suggestion for the comment, but otherwise looks ok to me.

lib/builtins/arm/aeabi_cdcmp.S

49

I think that the comment could be a bit more specific to the issue without needing to link to the pr.

For example "On some builds __aeabi_cdcmple may be in a different section so we use an IT followed by an unconditional branch to guarantee that we have a supported relocation on all platforms."

[manojgupta]

Thanks Peter, I Updated the comment.

[manojgupta]

Ping! Is it ok to land this?

[compnerd]

Please make sure that you do a build for watchOS before committing this, but this looks like it should accommodate that too.

lib/builtins/arm/aeabi_cdcmp.S

1:
         // Z = 0, C = 1
         movs r0, #0xF
         lsls r0, r0, #31
         pop {r0-r3, pc}
 #else
         pop {r0-r3, lr}
 
         // NaN has been ruled out, so __aeabi_cdcmple can't trap
+        // Use "it ne" + unconditional branch to guarantee a supported relocation if
+        // __aeabi_cdcmple is in a different section for some builds.
+        IT(ne)
         bne __aeabi_cdcmple
 
-#if defined(__ARM_ARCH_7M__) || defined(__ARM_ARCH_7EM__)
+#if defined(USE_THUMB_2)
         mov ip, #APSR_C
         msr APSR_nzcvq, ip
 #else
         msr CPSR_f, #APSR_C
 #endif
         JMP(lr)
 #endif
 END_COMPILERRT_FUNCTION(__aeabi_cdcmpeq)

lib/builtins/arm/aeabi_cfcmp.S

1:
         // Z = 0, C = 1
         movs r0, #0xF
         lsls r0, r0, #31
         pop {r0-r3, pc}
 #else
         pop {r0-r3, lr}
 
         // NaN has been ruled out, so __aeabi_cfcmple can't trap
+        // Use "it ne" + unconditional branch to guarantee a supported relocation if
+        // __aeabi_cfcmple is in a different section for some builds.
+        IT(ne)
         bne __aeabi_cfcmple
 
-#if defined(__ARM_ARCH_7M__) || defined(__ARM_ARCH_7EM__)
+#if defined(USE_THUMB_2)
         mov ip, #APSR_C
         msr APSR_nzcvq, ip
 #else
         msr CPSR_f, #APSR_C
 #endif
         JMP(lr)
 #endif
 END_COMPILERRT_FUNCTION(__aeabi_cfcmpeq)

lib/builtins/assembly.h

 #if defined(__arm__)
 
 /*
  * Determine actual [ARM][THUMB[1][2]] ISA using compiler predefined macros:
  * - for '-mthumb -march=armv6' compiler defines '__thumb__'
  * - for '-mthumb -march=armv7' compiler defines '__thumb__' and '__thumb2__'
  */
 #if defined(__thumb2__) || defined(__thumb__)
-#define DEFINE_CODE_STATE .thumb
+#define DEFINE_CODE_STATE .thumb SEPARATOR
 #define DECLARE_FUNC_ENCODING    .thumb_func SEPARATOR
 #if defined(__thumb2__)
 #define USE_THUMB_2
 #define IT(cond)  it cond
 #define ITT(cond) itt cond
 #define ITE(cond) ite cond
 #else
 #define USE_THUMB_1
 #define IT(cond)
 #define ITT(cond)
 #define ITE(cond)
 #endif // defined(__thumb__2)
 #else // !defined(__thumb2__) && !defined(__thumb__)
-#define DEFINE_CODE_STATE .arm
+#define DEFINE_CODE_STATE .arm SEPARATOR
 #define DECLARE_FUNC_ENCODING
 #define IT(cond)
 #define ITT(cond)
 #define ITE(cond)
 #endif
 
 #if defined(USE_THUMB_1) && defined(USE_THUMB_2)
 #error "USE_THUMB_1 and USE_THUMB_2 can't be defined together."

 
 #if defined(USE_THUMB_2)
 #define WIDE(op) op.w
 #else
 #define WIDE(op) op
 #endif
 #else // !defined(__arm)
 #define DECLARE_FUNC_ENCODING
+#define DEFINE_CODE_STATE
 #endif
 
 #define GLUE2(a, b) a##b
 #define GLUE(a, b) GLUE2(a, b)
 #define SYMBOL_NAME(name) GLUE(__USER_LABEL_PREFIX__, name)
 
 #ifdef VISIBILITY_HIDDEN
 #define DECLARE_SYMBOL_VISIBILITY(name)                                        \
   HIDDEN(SYMBOL_NAME(name)) SEPARATOR
 #else
 #define DECLARE_SYMBOL_VISIBILITY(name)
 #endif
 
 #define DEFINE_COMPILERRT_FUNCTION(name)                                       \
+  DEFINE_CODE_STATE                                                            \
   FILE_LEVEL_DIRECTIVE SEPARATOR                                               \
   .globl SYMBOL_NAME(name) SEPARATOR                                           \
   SYMBOL_IS_FUNC(SYMBOL_NAME(name)) SEPARATOR                                  \
   DECLARE_SYMBOL_VISIBILITY(name)                                              \
   DECLARE_FUNC_ENCODING                                                        \
   SYMBOL_NAME(name):
 
 #define DEFINE_COMPILERRT_THUMB_FUNCTION(name)                                 \
+  DEFINE_CODE_STATE                                                            \
   FILE_LEVEL_DIRECTIVE SEPARATOR                                               \
   .globl SYMBOL_NAME(name) SEPARATOR                                           \
   SYMBOL_IS_FUNC(SYMBOL_NAME(name)) SEPARATOR                                  \
   DECLARE_SYMBOL_VISIBILITY(name) SEPARATOR                                    \
   .thumb_func SEPARATOR                                                        \
   SYMBOL_NAME(name):
 
 #define DEFINE_COMPILERRT_PRIVATE_FUNCTION(name)                               \
+  DEFINE_CODE_STATE                                                            \
   FILE_LEVEL_DIRECTIVE SEPARATOR                                               \
   .globl SYMBOL_NAME(name) SEPARATOR                                           \
   SYMBOL_IS_FUNC(SYMBOL_NAME(name)) SEPARATOR                                  \
   HIDDEN(SYMBOL_NAME(name)) SEPARATOR                                          \
   DECLARE_FUNC_ENCODING                                                        \
   SYMBOL_NAME(name):
 
 #define DEFINE_COMPILERRT_PRIVATE_FUNCTION_UNMANGLED(name)                     \
+  DEFINE_CODE_STATE                                                            \
   .globl name SEPARATOR                                                        \
   SYMBOL_IS_FUNC(name) SEPARATOR                                               \
   HIDDEN(name) SEPARATOR                                                       \
   DECLARE_FUNC_ENCODING                                                        \
   name:
 
 #define DEFINE_COMPILERRT_FUNCTION_ALIAS(name, target)                         \
   .globl SYMBOL_NAME(name) SEPARATOR                                           \