[PATCH] [compiler-rt] Avoid undefined behaviour in __floatsisf and __floatsidf

[Matthew Fernandez via llvm-commits]

These two functions for soft floating point support negate their signed int argument if it is negative. In the case 
where the argument is INT_MIN, this negation is undefined behaviour with respect to the C standard. This change performs 
the negation on an unsigned value, avoiding the just-described situation. This change does not alter the intended 
semantics of these functions.

Signed-off-by: Matthew Fernandez <matthew.fernandez at gmail.com>

Index: lib/builtins/floatsidf.c
===================================================================
--- lib/builtins/floatsidf.c	(revision 251670)
+++ lib/builtins/floatsidf.c	(working copy)
@@ -33,7 +33,7 @@
      rep_t sign = 0;
      if (a < 0) {
          sign = signBit;
-        a = -a;
+        a = -(unsigned int)a;
      }

      // Exponent of (fp_t)a is the width of abs(a).
Index: lib/builtins/floatsisf.c
===================================================================
--- lib/builtins/floatsisf.c	(revision 251670)
+++ lib/builtins/floatsisf.c	(working copy)
@@ -33,7 +33,7 @@
      rep_t sign = 0;
      if (a < 0) {
          sign = signBit;
-        a = -a;
+        a = -(unsigned int)a;
      }

      // Exponent of (fp_t)a is the width of abs(a).