[gcc r11-5386] Improve abs with overflow implementations

[gcc r11-5386] Improve abs with overflow implementations

[Jeff Law]

https://gcc.gnu.org/g:4919ed711c1d02845f2843f6b0a70c27f9e6d434

commit r11-5386-g4919ed711c1d02845f2843f6b0a70c27f9e6d434
Author: Stefan Kanthak <stefan.kanthak@nexgo.de>
Date:   Wed Nov 25 11:36:51 2020 -0700

    Improve abs with overflow implementations
    
    libgcc/
    
            * libgcc2.c (absvSI2): Simplify/improve implementation by using
            builtin_add_overflow.
            (absvsi2, absvDI2): Likewise.

Diff:
---
 libgcc/libgcc2.c | 42 ++++++++++++------------------------------
 1 file changed, 12 insertions(+), 30 deletions(-)

diff --git a/libgcc/libgcc2.c b/libgcc/libgcc2.c
index cf0ca299c72..1921d80f612 100644
--- a/libgcc/libgcc2.c
+++ b/libgcc/libgcc2.c
@@ -214,37 +214,25 @@ __negvDI2 (DWtype a)
 Wtype
 __absvSI2 (Wtype a)
 {
-  Wtype w = a;
-
-  if (a < 0)
-#ifdef L_negvsi2
-    w = __negvSI2 (a);
-#else
-    w = -(UWtype) a;
+  const Wtype v = 0 - (a < 0);
+  Wtype w;
 
-  if (w < 0)
+  if (__builtin_add_overflow (a, v, &w))
     abort ();
-#endif
 
-   return w;
+  return v ^ w;
 }
 #ifdef COMPAT_SIMODE_TRAPPING_ARITHMETIC
 SItype
 __absvsi2 (SItype a)
 {
-  SItype w = a;
-
-  if (a < 0)
-#ifdef L_negvsi2
-    w = __negvsi2 (a);
-#else
-    w = -(USItype) a;
+  const SItype v = 0 - (a < 0);
+  SItype w;
 
-  if (w < 0)
+  if (__builtin_add_overflow (a, v, &w))
     abort ();
-#endif
 
-   return w;
+  return v ^ w;
 }
 #endif /* COMPAT_SIMODE_TRAPPING_ARITHMETIC */
 #endif
@@ -253,19 +241,13 @@ __absvsi2 (SItype a)
 DWtype
 __absvDI2 (DWtype a)
 {
-  DWtype w = a;
-
-  if (a < 0)
-#ifdef L_negvdi2
-    w = __negvDI2 (a);
-#else
-    w = -(UDWtype) a;
+  const DWtype v = 0 - (a < 0);
+  DWtype w;
 
-  if (w < 0)
+  if (__builtin_add_overflow (a, v, &w))
     abort ();
-#endif
 
-  return w;
+  return v ^ w;
 }
 #endif