1 files changed, 61 insertions, 0 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 36127b5..d10a815 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -76,6 +76,8 @@ extensions, accepted by GCC in C90 mode and in C++.
 * Offsetof::            Special syntax for implementing @code{offsetof}.
 * __sync Builtins::     Legacy built-in functions for atomic memory access.
 * __atomic Builtins::   Atomic built-in functions with memory model.
+* Integer Overflow Builtins:: Built-in functions to perform arithmetics and
+                        arithmetic overflow checking.
 * x86 specific memory model extensions for transactional memory:: x86 memory models.
 * Object Size Checking:: Built-in functions for limited buffer overflow
                         checking.
@@ -8487,6 +8489,65 @@ alignment.  A value of 0 indicates typical alignment should be used.  The
 compiler may also ignore this parameter.
 @end deftypefn
 
+@node Integer Overflow Builtins
+@section Built-in functions to perform arithmetics and arithmetic overflow checking.
+
+The following built-in functions allow performing simple arithmetic operations
+together with checking whether the operations overflowed.
+
+@deftypefn {Built-in Function} bool __builtin_add_overflow (@var{type1} a, @var{type2} b, @var{type3} *res)
+@deftypefnx {Built-in Function} bool __builtin_sadd_overflow (int a, int b, int *res)
+@deftypefnx {Built-in Function} bool __builtin_saddl_overflow (long int a, long int b, long int *res)
+@deftypefnx {Built-in Function} bool __builtin_saddll_overflow (long long int a, long long int b, long int *res)
+@deftypefnx {Built-in Function} bool __builtin_uadd_overflow (unsigned int a, unsigned int b, unsigned int *res)
+@deftypefnx {Built-in Function} bool __builtin_uaddl_overflow (unsigned long int a, unsigned long int b, unsigned long int *res)
+@deftypefnx {Built-in Function} bool __builtin_uaddll_overflow (unsigned long long int a, unsigned long long int b, unsigned long int *res)
+
+These built-in functions promote the first two operands into infinite precision signed
+type and perform addition on those promoted operands.  The result is then
+cast to the type the third pointer argument points to and stored there.
+If the stored result is equal to the infinite precision result, the built-in
+functions return false, otherwise they return true.  As the addition is
+performed in infinite signed precision, these built-in functions have fully defined
+behavior for all argument values.
+
+The first built-in function allows arbitrary integral types for operands and
+the result type must be pointer to some integer type, the rest of the built-in
+functions have explicit integer types.
+
+The compiler will attempt to use hardware instructions to implement
+these built-in functions where possible, like conditional jump on overflow
+after addition, conditional jump on carry etc.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __builtin_sub_overflow (@var{type1} a, @var{type2} b, @var{type3} *res)
+@deftypefnx {Built-in Function} bool __builtin_ssub_overflow (int a, int b, int *res)
+@deftypefnx {Built-in Function} bool __builtin_ssubl_overflow (long int a, long int b, long int *res)
+@deftypefnx {Built-in Function} bool __builtin_ssubll_overflow (long long int a, long long int b, long int *res)
+@deftypefnx {Built-in Function} bool __builtin_usub_overflow (unsigned int a, unsigned int b, unsigned int *res)
+@deftypefnx {Built-in Function} bool __builtin_usubl_overflow (unsigned long int a, unsigned long int b, unsigned long int *res)
+@deftypefnx {Built-in Function} bool __builtin_usubll_overflow (unsigned long long int a, unsigned long long int b, unsigned long int *res)
+
+These built-in functions are similar to the add overflow checking built-in
+functions above, except they perform subtraction, subtract the second argument
+from the first one, instead of addition.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __builtin_mul_overflow (@var{type1} a, @var{type2} b, @var{type3} *res)
+@deftypefnx {Built-in Function} bool __builtin_smul_overflow (int a, int b, int *res)
+@deftypefnx {Built-in Function} bool __builtin_smull_overflow (long int a, long int b, long int *res)
+@deftypefnx {Built-in Function} bool __builtin_smulll_overflow (long long int a, long long int b, long int *res)
+@deftypefnx {Built-in Function} bool __builtin_umul_overflow (unsigned int a, unsigned int b, unsigned int *res)
+@deftypefnx {Built-in Function} bool __builtin_umull_overflow (unsigned long int a, unsigned long int b, unsigned long int *res)
+@deftypefnx {Built-in Function} bool __builtin_umulll_overflow (unsigned long long int a, unsigned long long int b, unsigned long int *res)
+
+These built-in functions are similar to the add overflow checking built-in
+functions above, except they perform multiplication, instead of addition.
+
+@end deftypefn
+
 @node x86 specific memory model extensions for transactional memory
 @section x86 specific memory model extensions for transactional memory