Added code comments for clarification

Author: vhscampos

compiler-rt/test/builtins/Unit/arm/aeabi_idivmod_test.c

@@ -14,6 +14,12 @@ int test__aeabi_idivmod(si_int a, si_int b,
 {
 	  si_int rem;
     du_int ret = __aeabi_idivmod(a, b);
+    // __aeabi_idivmod actually returns a struct { quotient; remainder; } using
+    // value_in_regs calling convention. Due to the ABI rules, struct fields
+    // come in the same order regardless of endianness. However since the
+    // result is received here as a 64-bit integer, in which endianness does
+    // matter, the position of each component (quotient and remainder) varies
+    // depending on endianness.
 #  if _YUGA_BIG_ENDIAN
     rem = ret & 0xFFFFFFFF;
     si_int result = ret >> 32;

compiler-rt/test/builtins/Unit/arm/aeabi_uidivmod_test.c

@@ -13,6 +13,12 @@ int test__aeabi_uidivmod(su_int a, su_int b,
 						su_int expected_result, su_int expected_rem)
 {
     du_int ret = __aeabi_uidivmod(a, b);
+    // __aeabi_uidivmod actually returns a struct { quotient; remainder; }
+    // using value_in_regs calling convention. Due to the ABI rules, struct
+    // fields come in the same order regardless of endianness. However since
+    // the result is received here as a 64-bit integer, in which endianness
+    // does matter, the position of each component (quotient and remainder)
+    // varies depending on endianness.
 #  if _YUGA_BIG_ENDIAN
     su_int rem = ret & 0xFFFFFFFF;
     si_int result = ret >> 32;

compiler-rt/test/builtins/Unit/arm/aeabi_uldivmod_test.c

@@ -12,6 +12,10 @@ COMPILER_RT_ABI void /* __value_in_regs */ __aeabi_uldivmod(du_int a, du_int b);
 int test_aeabi_uldivmod(du_int a, du_int b, du_int expected_q, du_int expected_r)
 {
     du_int q, r;
+    // __aeabi_uldivmod returns a struct { quotient; remainder; } using
+    // value_in_regs calling convention. Each field is a 64-bit integer, so the
+    // quotient resides in r0 and r1, while the remainder in r2 and r3. The
+    // byte order however depends on the endianness.
     __asm__(
 #  if _YUGA_BIG_ENDIAN
         "movs r1, %Q[a] \n"