6 files changed, 77 insertions, 10 deletions

diff --git a/compiler-rt/lib/builtins/divdc3.c b/compiler-rt/lib/builtins/divdc3.c
index 3c88390b5e7..392d6ecacde 100644
--- a/compiler-rt/lib/builtins/divdc3.c
+++ b/compiler-rt/lib/builtins/divdc3.c
@@ -12,6 +12,8 @@
  * ===----------------------------------------------------------------------===
  */
 
+#define DOUBLE_PRECISION
+#include "fp_lib.h"
 #include "int_lib.h"
 #include "int_math.h"
 
@@ -21,7 +23,7 @@ COMPILER_RT_ABI Dcomplex
 __divdc3(double __a, double __b, double __c, double __d)
 {
     int __ilogbw = 0;
-    double __logbw = crt_logb(crt_fmax(crt_fabs(__c), crt_fabs(__d)));
+    double __logbw = __compiler_rt_logb(crt_fmax(crt_fabs(__c), crt_fabs(__d)));
     if (crt_isfinite(__logbw))
     {
         __ilogbw = (int)__logbw;
diff --git a/compiler-rt/lib/builtins/divsc3.c b/compiler-rt/lib/builtins/divsc3.c
index 42a48315e66..0d18a256c3d 100644
--- a/compiler-rt/lib/builtins/divsc3.c
+++ b/compiler-rt/lib/builtins/divsc3.c
@@ -12,6 +12,8 @@
  *===----------------------------------------------------------------------===
  */
 
+#define SINGLE_PRECISION
+#include "fp_lib.h"
 #include "int_lib.h"
 #include "int_math.h"
 
@@ -21,7 +23,8 @@ COMPILER_RT_ABI Fcomplex
 __divsc3(float __a, float __b, float __c, float __d)
 {
     int __ilogbw = 0;
-    float __logbw = crt_logbf(crt_fmaxf(crt_fabsf(__c), crt_fabsf(__d)));
+    float __logbw =
+        __compiler_rt_logbf(crt_fmaxf(crt_fabsf(__c), crt_fabsf(__d)));
     if (crt_isfinite(__logbw))
     {
         __ilogbw = (int)__logbw;
diff --git a/compiler-rt/lib/builtins/divtc3.c b/compiler-rt/lib/builtins/divtc3.c
index 16e538ba4a3..e5ea00d841e 100644
--- a/compiler-rt/lib/builtins/divtc3.c
+++ b/compiler-rt/lib/builtins/divtc3.c
@@ -12,6 +12,8 @@
  *===----------------------------------------------------------------------===
  */
 
+#define QUAD_PRECISION
+#include "fp_lib.h"
 #include "int_lib.h"
 #include "int_math.h"
 
@@ -21,7 +23,8 @@ COMPILER_RT_ABI Lcomplex
 __divtc3(long double __a, long double __b, long double __c, long double __d)
 {
     int __ilogbw = 0;
-    long double __logbw = crt_logbl(crt_fmaxl(crt_fabsl(__c), crt_fabsl(__d)));
+    long double __logbw =
+        __compiler_rt_logbl(crt_fmaxl(crt_fabsl(__c), crt_fabsl(__d)));
     if (crt_isfinite(__logbw))
     {
         __ilogbw = (int)__logbw;
diff --git a/compiler-rt/lib/builtins/fp_lib.h b/compiler-rt/lib/builtins/fp_lib.h
index 223fb980aae..a0e19ab6a8f 100644
--- a/compiler-rt/lib/builtins/fp_lib.h
+++ b/compiler-rt/lib/builtins/fp_lib.h
@@ -25,6 +25,7 @@
 #include <stdbool.h>
 #include <limits.h>
 #include "int_lib.h"
+#include "int_math.h"
 
 // x86_64 FreeBSD prior v9.3 define fixed-width types incorrectly in
 // 32-bit mode.
@@ -265,6 +266,62 @@ static __inline void wideRightShiftWithSticky(rep_t *hi, rep_t *lo, unsigned int
         *hi = 0;
     }
 }
+
+// Implements logb methods (logb, logbf, logbl) for IEEE-754. This avoids
+// pulling in a libm dependency from compiler-rt, but is not meant to replace
+// it (i.e. code calling logb() should get the one from libm, not this), hence
+// the __compiler_rt prefix.
+static __inline fp_t __compiler_rt_logbX(fp_t x) {
+  rep_t rep = toRep(x);
+  int exp = (rep & exponentMask) >> significandBits;
+
+  // Abnormal cases:
+  // 1) +/- inf returns +inf; NaN returns NaN
+  // 2) 0.0 returns -inf
+  if (exp == maxExponent) {
+    if (((rep & signBit) == 0) || (x != x)) {
+      return x;  // NaN or +inf: return x
+    } else {
+      return -x;  // -inf: return -x
+    }
+  } else if (x == 0.0) {
+    // 0.0: return -inf
+    return fromRep(infRep | signBit);
+  }
+
+  if (exp != 0) {
+    // Normal number
+    return exp - exponentBias;  // Unbias exponent
+  } else {
+    // Subnormal number; normalize and repeat
+    rep &= absMask;
+    const int shift = 1 - normalize(&rep);
+    exp = (rep & exponentMask) >> significandBits;
+    return exp - exponentBias - shift;  // Unbias exponent
+  }
+}
+#endif
+
+#if defined(SINGLE_PRECISION)
+static __inline fp_t __compiler_rt_logbf(fp_t x) {
+  return __compiler_rt_logbX(x);
+}
+#elif defined(DOUBLE_PRECISION)
+static __inline fp_t __compiler_rt_logb(fp_t x) {
+  return __compiler_rt_logbX(x);
+}
+#elif defined(QUAD_PRECISION)
+  #if defined(CRT_LDBL_128BIT)
+static __inline fp_t __compiler_rt_logbl(fp_t x) {
+  return __compiler_rt_logbX(x);
+}
+  #else
+// The generic implementation only works for ieee754 floating point. For other
+// floating point types, continue to rely on the libm implementation for now.
+static __inline long double __compiler_rt_logbl(long double x) {
+  return crt_logbl(x);
+}
+  #endif
 #endif
 
 #endif // FP_LIB_HEADER
diff --git a/compiler-rt/lib/builtins/int_math.h b/compiler-rt/lib/builtins/int_math.h
index fc81fb7f022..aa3d0721a8a 100644
--- a/compiler-rt/lib/builtins/int_math.h
+++ b/compiler-rt/lib/builtins/int_math.h
@@ -92,12 +92,8 @@
 #endif
 
 #if defined(_MSC_VER) && !defined(__clang__)
-#define crt_logb(x) logb((x))
-#define crt_logbf(x) logbf((x))
 #define crt_logbl(x) logbl((x))
 #else
-#define crt_logb(x) __builtin_logb((x))
-#define crt_logbf(x) __builtin_logbf((x))
 #define crt_logbl(x) __builtin_logbl((x))
 #endif
 
diff --git a/compiler-rt/lib/builtins/ppc/divtc3.c b/compiler-rt/lib/builtins/ppc/divtc3.c
index 8ec41c528ab..ef532b84114 100644
--- a/compiler-rt/lib/builtins/ppc/divtc3.c
+++ b/compiler-rt/lib/builtins/ppc/divtc3.c
@@ -4,6 +4,11 @@
 
 #include "DD.h"
 #include "../int_math.h"
+// Use DOUBLE_PRECISION because the soft-fp method we use is logb (on the upper
+// half of the long doubles), even though this file defines complex division for
+// 128-bit floats.
+#define DOUBLE_PRECISION
+#include "../fp_lib.h"
 
 #if !defined(CRT_INFINITY) && defined(HUGE_VAL)
 #define CRT_INFINITY HUGE_VAL
@@ -21,9 +26,10 @@ __divtc3(long double a, long double b, long double c, long double d)
 	DD dDD = { .ld = d };
 	
 	int ilogbw = 0;
-	const double logbw = crt_logb(crt_fmax(crt_fabs(cDD.s.hi), crt_fabs(dDD.s.hi) ));
-	
-	if (crt_isfinite(logbw))
+	const double logbw = __compiler_rt_logb(
+		crt_fmax(crt_fabs(cDD.s.hi), crt_fabs(dDD.s.hi)));
+
+        if (crt_isfinite(logbw))
 	{
 		ilogbw = (int)logbw;