[Bug target/100119] [x86] Conversion unsigned int -> double produces -0 (-m32 -msse2 -mfpmath=sse)

[ubizjak at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100119

--- Comment #2 from Uroš Bizjak <ubizjak at gmail dot com> ---
diff --git a/gcc/config/i386/i386-expand.c b/gcc/config/i386/i386-expand.c
index dda08ff67f2..5a7a00c13bd 100644
--- a/gcc/config/i386/i386-expand.c
+++ b/gcc/config/i386/i386-expand.c
@@ -1550,6 +1550,8 @@ ix86_expand_convert_uns_sixf_sse (rtx, rtx)
   gcc_unreachable ();
 }

+static rtx ix86_expand_sse_fabs (rtx op0, rtx *smask);
+
 /* Convert an unsigned SImode value into a DFmode.  Only currently used
    for SSE, but applicable anywhere.  */

@@ -1569,6 +1571,11 @@ ix86_expand_convert_uns_sidf_sse (rtx target, rtx input)
   x = const_double_from_real_value (TWO31r, DFmode);

   x = expand_simple_binop (DFmode, PLUS, fp, x, target, 0, OPTAB_DIRECT);
+
+  /* Remove the sign with FE_DOWNWARD, where x - x = -0.0.  */
+  if (HONOR_SIGNED_ZEROS (DFmode) && flag_rounding_math)
+    x = ix86_expand_sse_fabs (x, NULL);
+
   if (x != target)
     emit_move_insn (target, x);
 }