[builtins] Generate __multc3 for z/OS (#77554)

#68132 ended up removing
__multc3 & __divtc3 from compiler-rt library builds that have
QUAD_PRECISION but not TF_MODE due to missing int128 support. I added support for QUAD_PRECISION to
use the native hex float long double representation.

---------

Co-authored-by: Alexander Richardson <mail@alexrichardson.me>

Author: perry-ca

compiler-rt/lib/builtins/divtc3.c

@@ -13,7 +13,7 @@
 #define QUAD_PRECISION
 #include "fp_lib.h"
 
-#if defined(CRT_HAS_TF_MODE)
+#if defined(CRT_HAS_F128)
 
 // Returns: the quotient of (a + ib) / (c + id)
 

compiler-rt/lib/builtins/fp_lib.h

@@ -188,6 +188,8 @@ static __inline void wideMultiply(rep_t a, rep_t b, rep_t *hi, rep_t *lo) {
 #undef Word_HiMask
 #undef Word_LoMask
 #undef Word_FullMask
+#else
+typedef long double fp_t;
 #endif // defined(CRT_HAS_TF_MODE)
 #else
 #error SINGLE_PRECISION, DOUBLE_PRECISION or QUAD_PRECISION must be defined.
@@ -374,10 +376,10 @@ static __inline fp_t __compiler_rt_fmax(fp_t x, fp_t y) {
 #endif
 }
 
-#elif defined(QUAD_PRECISION) && defined(CRT_HAS_TF_MODE)
+#elif defined(QUAD_PRECISION)
 // The generic implementation only works for ieee754 floating point. For other
 // floating point types, continue to rely on the libm implementation for now.
-#if defined(CRT_HAS_IEEE_TF)
+#if defined(CRT_HAS_IEEE_TF) && defined(CRT_HAS_128BIT)
 static __inline tf_float __compiler_rt_logbtf(tf_float x) {
   return __compiler_rt_logbX(x);
 }
@@ -405,6 +407,8 @@ static __inline tf_float __compiler_rt_fmaxtf(tf_float x, tf_float y) {
 #define __compiler_rt_logbl crt_logbl
 #define __compiler_rt_scalbnl crt_scalbnl
 #define __compiler_rt_fmaxl crt_fmaxl
+#define crt_fabstf crt_fabsl
+#define crt_copysigntf crt_copysignl
 #else
 #error Unsupported TF mode type
 #endif

compiler-rt/lib/builtins/int_types.h

@@ -189,12 +189,16 @@ typedef long double tf_float;
 #define CRT_LDBL_IEEE_F128
 #endif
 #define TF_C(x) x##L
-#elif __LDBL_MANT_DIG__ == 113
-// Use long double instead of __float128 if it matches the IEEE 128-bit format.
+#elif __LDBL_MANT_DIG__ == 113 ||                                              \
+    (__FLT_RADIX__ == 16 && __LDBL_MANT_DIG__ == 28)
+// Use long double instead of __float128 if it matches the IEEE 128-bit format
+// or the IBM hexadecimal format.
 #define CRT_LDBL_128BIT
 #define CRT_HAS_F128
+#if __LDBL_MANT_DIG__ == 113
 #define CRT_HAS_IEEE_TF
 #define CRT_LDBL_IEEE_F128
+#endif
 typedef long double tf_float;
 #define TF_C(x) x##L
 #elif defined(__FLOAT128__) || defined(__SIZEOF_FLOAT128__)

compiler-rt/lib/builtins/multc3.c

@@ -15,7 +15,7 @@
 #include "int_lib.h"
 #include "int_math.h"
 
-#if defined(CRT_HAS_TF_MODE)
+#if defined(CRT_HAS_F128)
 
 // Returns: the product of a + ib and c + id