libgcc: Avoid signed negation overflow in __powi?f2 [PR99236]

When these functions are called with integer minimum, there is UB on the libgcc
side.  Fixed in the obvious way, the code in the end wants ABSU_EXPR behavior.

2021-02-24  Jakub Jelinek  <jakub@redhat.com>

	PR libgcc/99236
	* libgcc2.c (__powisf2, __powidf2, __powitf2, __powixf2): Perform
	negation of m in unsigned type.

diff --git a/libgcc/libgcc2.c b/libgcc/libgcc2.c
index 960f594..17de0a7 100644 (file)
--- a/libgcc/libgcc2.c
+++ b/libgcc/libgcc2.c
@@ -1834,7 +1834,7 @@ __fixunssfSI (SFtype a)
 TYPE
 NAME (TYPE x, int m)
 {
-  unsigned int n = m < 0 ? -m : m;
+  unsigned int n = m < 0 ? -(unsigned int) m : (unsigned int) m;
   TYPE y = n % 2 ? x : 1;
   while (n >>= 1)
     {