diff --git a/compiler-rt/lib/builtins/fixdfdi.c b/compiler-rt/lib/builtins/fixdfdi.c
--- a/compiler-rt/lib/builtins/fixdfdi.c
+++ b/compiler-rt/lib/builtins/fixdfdi.c
@@ -27,8 +27,8 @@
 // flags to set, and we don't want to code-gen to an unknown soft-float
 // implementation.
 
-typedef di_int fixint_t;
-typedef du_int fixuint_t;
+#define fixint_t di_int
+#define fixuint_t du_int
 #include "fp_fixint_impl.inc"
 
 COMPILER_RT_ABI di_int __fixdfdi(fp_t a) { return __fixint(a); }
diff --git a/compiler-rt/lib/builtins/fixdfsi.c b/compiler-rt/lib/builtins/fixdfsi.c
--- a/compiler-rt/lib/builtins/fixdfsi.c
+++ b/compiler-rt/lib/builtins/fixdfsi.c
@@ -8,8 +8,8 @@
 
 #define DOUBLE_PRECISION
 #include "fp_lib.h"
-typedef si_int fixint_t;
-typedef su_int fixuint_t;
+#define fixint_t si_int
+#define fixuint_t su_int
 #include "fp_fixint_impl.inc"
 
 COMPILER_RT_ABI si_int __fixdfsi(fp_t a) { return __fixint(a); }
diff --git a/compiler-rt/lib/builtins/fixdfti.c b/compiler-rt/lib/builtins/fixdfti.c
--- a/compiler-rt/lib/builtins/fixdfti.c
+++ b/compiler-rt/lib/builtins/fixdfti.c
@@ -12,8 +12,8 @@
 #define DOUBLE_PRECISION
 #include "fp_lib.h"
 
-typedef ti_int fixint_t;
-typedef tu_int fixuint_t;
+#define fixint_t ti_int
+#define fixuint_t tu_int
 #include "fp_fixint_impl.inc"
 
 COMPILER_RT_ABI ti_int __fixdfti(fp_t a) { return __fixint(a); }
diff --git a/compiler-rt/lib/builtins/fixsfdi.c b/compiler-rt/lib/builtins/fixsfdi.c
--- a/compiler-rt/lib/builtins/fixsfdi.c
+++ b/compiler-rt/lib/builtins/fixsfdi.c
@@ -27,8 +27,8 @@
 // flags to set, and we don't want to code-gen to an unknown soft-float
 // implementation.
 
-typedef di_int fixint_t;
-typedef du_int fixuint_t;
+#define fixint_t di_int
+#define fixuint_t du_int
 #include "fp_fixint_impl.inc"
 
 COMPILER_RT_ABI di_int __fixsfdi(fp_t a) { return __fixint(a); }
diff --git a/compiler-rt/lib/builtins/fixsfsi.c b/compiler-rt/lib/builtins/fixsfsi.c
--- a/compiler-rt/lib/builtins/fixsfsi.c
+++ b/compiler-rt/lib/builtins/fixsfsi.c
@@ -8,8 +8,8 @@
 
 #define SINGLE_PRECISION
 #include "fp_lib.h"
-typedef si_int fixint_t;
-typedef su_int fixuint_t;
+#define fixint_t si_int
+#define fixuint_t su_int
 #include "fp_fixint_impl.inc"
 
 COMPILER_RT_ABI si_int __fixsfsi(fp_t a) { return __fixint(a); }
diff --git a/compiler-rt/lib/builtins/fixsfti.c b/compiler-rt/lib/builtins/fixsfti.c
--- a/compiler-rt/lib/builtins/fixsfti.c
+++ b/compiler-rt/lib/builtins/fixsfti.c
@@ -11,9 +11,8 @@
 #ifdef CRT_HAS_128BIT
 #define SINGLE_PRECISION
 #include "fp_lib.h"
-
-typedef ti_int fixint_t;
-typedef tu_int fixuint_t;
+#define fixint_t ti_int
+#define fixuint_t tu_int
 #include "fp_fixint_impl.inc"
 
 COMPILER_RT_ABI ti_int __fixsfti(fp_t a) { return __fixint(a); }
diff --git a/compiler-rt/lib/builtins/fixtfdi.c b/compiler-rt/lib/builtins/fixtfdi.c
--- a/compiler-rt/lib/builtins/fixtfdi.c
+++ b/compiler-rt/lib/builtins/fixtfdi.c
@@ -10,8 +10,8 @@
 #include "fp_lib.h"
 
 #if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
-typedef di_int fixint_t;
-typedef du_int fixuint_t;
+#define fixint_t di_int
+#define fixuint_t du_int
 #include "fp_fixint_impl.inc"
 
 COMPILER_RT_ABI di_int __fixtfdi(fp_t a) { return __fixint(a); }
diff --git a/compiler-rt/lib/builtins/fixtfsi.c b/compiler-rt/lib/builtins/fixtfsi.c
--- a/compiler-rt/lib/builtins/fixtfsi.c
+++ b/compiler-rt/lib/builtins/fixtfsi.c
@@ -10,8 +10,8 @@
 #include "fp_lib.h"
 
 #if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
-typedef si_int fixint_t;
-typedef su_int fixuint_t;
+#define fixint_t si_int
+#define fixuint_t su_int
 #include "fp_fixint_impl.inc"
 
 COMPILER_RT_ABI si_int __fixtfsi(fp_t a) { return __fixint(a); }
diff --git a/compiler-rt/lib/builtins/fixtfti.c b/compiler-rt/lib/builtins/fixtfti.c
--- a/compiler-rt/lib/builtins/fixtfti.c
+++ b/compiler-rt/lib/builtins/fixtfti.c
@@ -10,8 +10,8 @@
 #include "fp_lib.h"
 
 #if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
-typedef ti_int fixint_t;
-typedef tu_int fixuint_t;
+#define fixint_t ti_int
+#define fixuint_t tu_int
 #include "fp_fixint_impl.inc"
 
 COMPILER_RT_ABI ti_int __fixtfti(fp_t a) { return __fixint(a); }
diff --git a/compiler-rt/lib/builtins/fp_fixint_impl.inc b/compiler-rt/lib/builtins/fp_fixint_impl.inc
--- a/compiler-rt/lib/builtins/fp_fixint_impl.inc
+++ b/compiler-rt/lib/builtins/fp_fixint_impl.inc
@@ -14,8 +14,8 @@
 #include "fp_lib.h"
 
 static __inline fixint_t __fixint(fp_t a) {
-  const fixint_t fixint_max = (fixint_t)((~(fixuint_t)0) / 2);
-  const fixint_t fixint_min = -fixint_max - 1;
+  const fixint_t fixint_max = MAX_SIGNED(fixint_t);
+  const fixint_t fixint_min = MIN_SIGNED(fixint_t);
   // Break a into sign, exponent, significand parts.
   const rep_t aRep = toRep(a);
   const rep_t aAbs = aRep & absMask;
diff --git a/compiler-rt/lib/builtins/int_mulo_impl.inc b/compiler-rt/lib/builtins/int_mulo_impl.inc
--- a/compiler-rt/lib/builtins/int_mulo_impl.inc
+++ b/compiler-rt/lib/builtins/int_mulo_impl.inc
@@ -16,10 +16,21 @@
 
 // Effects: sets *overflow to 1  if a * b overflows
 
-static __inline fixint_t __muloXi4(fixint_t a, fixint_t b, int *overflow) {
-  const int N = (int)(sizeof(fixint_t) * CHAR_BIT);
-  const fixint_t MIN = (fixint_t)1 << (N - 1);
-  const fixint_t MAX = ~MIN;
+// UBSan may be useful for testing the compiler-rt/builtins library by manually
+// setting CFLAGS="-fsanitize=undefined -fsanitize-undefined-trap-on-error"
+// when configuring compiler-rt and then running check-builtins.
+// The problem with __mulo[sdt]i4 LibCalls is that they may recursively call
+// themselves indefinitely when compiled with UBSan.
+#if defined(__clang__)
+#define NO_UBSAN __attribute__((no_sanitize("undefined")))
+#else
+#define NO_UBSAN
+#endif
+
+static __inline NO_UBSAN fixint_t __muloXi4(fixint_t a, fixint_t b, int *overflow) {
+  const int N = bitsizeof(fixint_t);
+  const fixint_t MIN = MIN_SIGNED(fixint_t);
+  const fixint_t MAX = MAX_SIGNED(fixint_t);
   *overflow = 0;
   fixint_t result = a * b;
   if (a == MIN) {
diff --git a/compiler-rt/lib/builtins/int_mulv_impl.inc b/compiler-rt/lib/builtins/int_mulv_impl.inc
--- a/compiler-rt/lib/builtins/int_mulv_impl.inc
+++ b/compiler-rt/lib/builtins/int_mulv_impl.inc
@@ -17,9 +17,9 @@
 // Effects: aborts if a * b overflows
 
 static __inline fixint_t __mulvXi3(fixint_t a, fixint_t b) {
-  const int N = (int)(sizeof(fixint_t) * CHAR_BIT);
-  const fixint_t MIN = (fixint_t)1 << (N - 1);
-  const fixint_t MAX = ~MIN;
+  const int N = bitsizeof(fixint_t);
+  const fixint_t MIN = MIN_SIGNED(fixint_t);
+  const fixint_t MAX = MAX_SIGNED(fixint_t);
   if (a == MIN) {
     if (b == 0 || b == 1)
       return a * b;
diff --git a/compiler-rt/lib/builtins/int_types.h b/compiler-rt/lib/builtins/int_types.h
--- a/compiler-rt/lib/builtins/int_types.h
+++ b/compiler-rt/lib/builtins/int_types.h
@@ -1,4 +1,4 @@
-//===-- int_lib.h - configuration header for compiler-rt  -----------------===//
+//===-- int_types.h - type definitions for compiler-rt --------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -37,6 +37,30 @@
 typedef int64_t di_int;
 typedef uint64_t du_int;
 
+// Helpers for standard type aliases to get signed from unsigned and vice versa
+#define AS_SIGNED(type) type##_AS_SIGNED
+#define AS_UNSIGNED(type) type##_AS_UNSIGNED
+#define si_int_AS_SIGNED si_int
+#define su_int_AS_SIGNED si_int
+#define di_int_AS_SIGNED di_int
+#define du_int_AS_SIGNED di_int
+#define ti_int_AS_SIGNED ti_int
+#define tu_int_AS_SIGNED ti_int
+#define si_int_AS_UNSIGNED su_int
+#define su_int_AS_UNSIGNED su_int
+#define di_int_AS_UNSIGNED du_int
+#define du_int_AS_UNSIGNED du_int
+#define ti_int_AS_UNSIGNED tu_int
+#define tu_int_AS_UNSIGNED tu_int
+
+// Misc macroses incapsulating common hacks.
+// Supposed to replace the ad-hoc UB-prone implementations.
+#define bitsizeof(type_or_value) ((int)(sizeof(type_or_value) * CHAR_BIT))
+#define SIGN_BIT(type) ((AS_UNSIGNED(type))1 << (bitsizeof(type) - 1))
+#define MIN_SIGNED(type) ((AS_SIGNED(type))SIGN_BIT(type))
+#define MAX_SIGNED(type) ((AS_SIGNED(type))(SIGN_BIT(type) - 1U))
+#define MAX_UNSIGNED(type) (~(AS_UNSIGNED(type))0))
+
 typedef union {
   di_int all;
   struct {
diff --git a/compiler-rt/lib/builtins/negdi2.c b/compiler-rt/lib/builtins/negdi2.c
--- a/compiler-rt/lib/builtins/negdi2.c
+++ b/compiler-rt/lib/builtins/negdi2.c
@@ -17,5 +17,5 @@
 COMPILER_RT_ABI di_int __negdi2(di_int a) {
   // Note: this routine is here for API compatibility; any sane compiler
   // should expand it inline.
-  return -a;
+  return -(du_int)a;
 }
diff --git a/compiler-rt/lib/builtins/negti2.c b/compiler-rt/lib/builtins/negti2.c
--- a/compiler-rt/lib/builtins/negti2.c
+++ b/compiler-rt/lib/builtins/negti2.c
@@ -19,7 +19,7 @@
 COMPILER_RT_ABI ti_int __negti2(ti_int a) {
   // Note: this routine is here for API compatibility; any sane compiler
   // should expand it inline.
-  return -a;
+  return -(tu_int)a;
 }
 
 #endif // CRT_HAS_128BIT
diff --git a/compiler-rt/lib/builtins/negvdi2.c b/compiler-rt/lib/builtins/negvdi2.c
--- a/compiler-rt/lib/builtins/negvdi2.c
+++ b/compiler-rt/lib/builtins/negvdi2.c
@@ -17,8 +17,7 @@
 // Effects: aborts if -a overflows
 
 COMPILER_RT_ABI di_int __negvdi2(di_int a) {
-  const di_int MIN = (di_int)1 << ((int)(sizeof(di_int) * CHAR_BIT) - 1);
-  if (a == MIN)
+  if (a == MIN_SIGNED(di_int))
     compilerrt_abort();
   return -a;
 }
diff --git a/compiler-rt/lib/builtins/negvsi2.c b/compiler-rt/lib/builtins/negvsi2.c
--- a/compiler-rt/lib/builtins/negvsi2.c
+++ b/compiler-rt/lib/builtins/negvsi2.c
@@ -17,8 +17,7 @@
 // Effects: aborts if -a overflows
 
 COMPILER_RT_ABI si_int __negvsi2(si_int a) {
-  const si_int MIN = (si_int)1 << ((int)(sizeof(si_int) * CHAR_BIT) - 1);
-  if (a == MIN)
+  if (a == MIN_SIGNED(si_int))
     compilerrt_abort();
   return -a;
 }
diff --git a/compiler-rt/lib/builtins/negvti2.c b/compiler-rt/lib/builtins/negvti2.c
--- a/compiler-rt/lib/builtins/negvti2.c
+++ b/compiler-rt/lib/builtins/negvti2.c
@@ -19,8 +19,7 @@
 // Effects: aborts if -a overflows
 
 COMPILER_RT_ABI ti_int __negvti2(ti_int a) {
-  const ti_int MIN = (ti_int)1 << ((int)(sizeof(ti_int) * CHAR_BIT) - 1);
-  if (a == MIN)
+  if (a == MIN_SIGNED(ti_int))
     compilerrt_abort();
   return -a;
 }