sim: bfin: fix ASTAT/correctness issues with arithmetic shifts

This improves some of the arithmetic shifts to better match the
hardware (especially wrt ASTAT behavior).  We hit areas where
the published documentation is thin so we have to rely on tests
run on the hardware to figure out how things should behave.

Signed-off-by: Robin Getz <robin.getz@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

1 files changed, 60 insertions, 10 deletions

diff --git a/sim/bfin/bfin-sim.c b/sim/bfin/bfin-sim.c
index 03b9d7a..e3201ef 100644
--- a/sim/bfin/bfin-sim.c
+++ b/sim/bfin/bfin-sim.c
@@ -5716,6 +5716,26 @@ decode_dsp32shift_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
     illegal_instruction (cpu);
 }
 
+static bu64
+sgn_extend (bu40 org, bu40 val, int size)
+{
+  bu64 ret = val;
+
+  if (org & (1ULL << (size - 1)))
+    {
+      /* We need to shift in to the MSB which is set.  */
+      int n;
+
+      for (n = 40; n >= 0; n--)
+	if (ret & (1ULL << n))
+	  break;
+      ret |= (-1ULL << n);
+    }
+  else
+    ret &= ~(-1ULL << 39);
+
+  return ret;
+}
 static void
 decode_dsp32shiftimm_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
 {
@@ -5765,8 +5785,37 @@ decode_dsp32shiftimm_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
 	{
 	  TRACE_INSN (cpu, "R%i.%c = R%i.%c >>> %i (S);",
 		      dst0, (HLs & 2) ? 'H' : 'L',
-		      src1, (HLs & 1) ? 'H' : 'L', immag);
-	  result = lshift (cpu, in, immag, 16, 1, 1);
+		      src1, (HLs & 1) ? 'H' : 'L', newimmag);
+	  if (newimmag > 16)
+	    {
+	      int shift = 32 - newimmag;
+	      bu16 inshift = in << shift;
+
+	      if (((inshift & ~0xFFFF)
+		   && ((inshift & ~0xFFFF) >> 16) != ~(~0 << shift))
+		  || (inshift & 0x8000) != (in & 0x8000))
+		{
+		  if (in & 0x8000)
+		    result = 0x8000;
+		  else
+		    result = 0x7fff;
+		  SET_ASTATREG (v, 1);
+		  SET_ASTATREG (vs, 1);
+		}
+	      else
+		{
+		  result = inshift;
+		  SET_ASTATREG (v, 0);
+		}
+
+	      SET_ASTATREG (az, !result);
+	      SET_ASTATREG (an, !!(result & 0x8000));
+	    }
+	  else
+	    {
+	      result = ashiftrt (cpu, in, newimmag, 16);
+	      result = sgn_extend (in, result, 16);
+	    }
 	}
       else if (sop == 2 && bit8)
 	{
@@ -5808,22 +5857,23 @@ decode_dsp32shiftimm_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
   else if (sop == 0 && sopcde == 3 && bit8 == 1)
     {
       /* Arithmetic shift, so shift in sign bit copies.  */
-      bu64 acc;
+      bu64 acc, val;
       int shift = uimm5 (newimmag);
       HLs = !!HLs;
 
       TRACE_INSN (cpu, "A%i = A%i >>> %i;", HLs, HLs, shift);
 
       acc = get_extended_acc (cpu, HLs);
-      acc >>= shift;
+      val = acc >> shift;
+
       /* Sign extend again.  */
-      if (acc & (1ULL << 39))
-	acc |= -(1ULL << 39);
-      else
-	acc &= ~(-(1ULL << 39));
+      val = sgn_extend (acc, val, 40);
 
-      STORE (AXREG (HLs), (acc >> 32) & 0xFF);
-      STORE (AWREG (HLs), acc & 0xFFFFFFFF);
+      STORE (AXREG (HLs), (val >> 32) & 0xFF);
+      STORE (AWREG (HLs), val & 0xFFFFFFFF);
+      STORE (ASTATREG (an), !!(val & (1ULL << 39)));
+      STORE (ASTATREG (az), !val);
+      STORE (ASTATREG (av[HLs]), 0);
     }
   else if ((sop == 0 && sopcde == 3 && bit8 == 0)
 	   || (sop == 1 && sopcde == 3))