sim: bfin: fix corner case Logical shift issues

From: Robin Getz <robin.getz@analog.com>

Overflow with shift operations happens independently of saturation, but
we have the logic merged.  Extend the lshift function so that callers
can tell it when to handle each independently, and then do so when it's
needed.

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

2 files changed, 64 insertions, 45 deletions

diff --git a/sim/bfin/ChangeLog b/sim/bfin/ChangeLog
index bac48f3..35863c9 100644
--- a/sim/bfin/ChangeLog
+++ b/sim/bfin/ChangeLog
@@ -1,3 +1,14 @@
+2012-03-19  Robin Getz  <robin.getz@analog.com>
+	    Mike Frysinger  <vapier@gentoo.org>
+
+	* bfin-sim.c (lshift): Add an overflow flag.  Delete now unused
+	i, j, and tmp vars.  Add a new v_i var.  Split the overflow logic
+	out from the saturate logic.  Do not set V ASTAT bits when working
+	with accumulators.
+	(decode_ALU2op_0): Add new argument to lshift call.
+	(decode_LOGI2op_0, decode_dsp32shift_0, decode_dsp32shiftimm_0):
+	Likewise.
+
 2012-03-18  Mike Frysinger  <vapier@gentoo.org>
 
 	* dv-bfin_ebiu_amc.c (struct bfin_ebiu_amc): Add bank_base.
diff --git a/sim/bfin/bfin-sim.c b/sim/bfin/bfin-sim.c
index ef7362b..2c93e04 100644
--- a/sim/bfin/bfin-sim.c
+++ b/sim/bfin/bfin-sim.c
@@ -748,12 +748,12 @@ lshiftrt (SIM_CPU *cpu, bu64 val, int cnt, int size)
 }
 
 static bu64
-lshift (SIM_CPU *cpu, bu64 val, int cnt, int size, bool saturate)
+lshift (SIM_CPU *cpu, bu64 val, int cnt, int size, bool saturate, bool overflow)
 {
-  int i, j, real_cnt = cnt > size ? size : cnt;
+  int v_i, real_cnt = cnt > size ? size : cnt;
   bu64 sgn = ~((val >> (size - 1)) - 1);
   int mask_cnt = size - 1;
-  bu64 masked, new_val = val, tmp;
+  bu64 masked, new_val = val;
   bu64 mask = ~0;
 
   mask <<= mask_cnt;
@@ -777,31 +777,35 @@ lshift (SIM_CPU *cpu, bu64 val, int cnt, int size, bool saturate)
 
      However, it's a little more complex than looking at sign bits, we need
      to see if we are shifting the sign information away...  */
-  tmp = val & ((~mask << 1) | 1);
-
-  j = 0;
-  for (i = 1; i <= real_cnt && saturate; i++)
-    {
-      if ((tmp & ((bu64)1 << (size - 1))) !=
-	  (((val >> mask_cnt) & 0x1) << mask_cnt))
-	j++;
-      tmp <<= 1;
-    }
-  saturate &= (!sgn && (new_val & (1 << mask_cnt)))
-	      || (sgn && !(new_val & (1 << mask_cnt)));
+  if (((val << cnt) >> size) == 0
+      || (((val << cnt) >> size) == ~(~0 << cnt)
+	  && ((new_val >> (size - 1)) & 0x1)))
+    v_i = 0;
+  else
+    v_i = 1;
 
   switch (size)
     {
     case 16:
-      if (j || (saturate && (new_val & mask)))
-	new_val = sgn == 0 ? 0x7fff : 0x8000, saturate = 1;
       new_val &= 0xFFFF;
+      if (saturate && (v_i || ((val >> (size - 1)) != (new_val >> (size - 1)))))
+	{
+	  new_val = (val >> (size - 1)) == 0 ? 0x7fff : 0x8000;
+	  v_i = 1;
+	}
       break;
     case 32:
       new_val &= 0xFFFFFFFF;
       masked &= 0xFFFFFFFF;
-      if (j || (saturate && ((sgn != masked) || (!sgn && new_val == 0))))
-	new_val = sgn == 0 ? 0x7fffffff : 0x80000000, saturate = 1;
+      sgn &= 0xFFFFFFFF;
+      if (saturate
+	  && (v_i
+	      || (sgn != masked)
+	      || (!sgn && new_val == 0 && val != 0)))
+	{
+	  new_val = sgn == 0 ? 0x7fffffff : 0x80000000;
+	  v_i = 1;
+	}
       break;
     case 40:
       new_val &= 0xFFFFFFFFFFull;
@@ -814,9 +818,13 @@ lshift (SIM_CPU *cpu, bu64 val, int cnt, int size, bool saturate)
 
   SET_ASTATREG (an, new_val >> (size - 1));
   SET_ASTATREG (az, new_val == 0);
-  SET_ASTATREG (v, !!(saturate || j));
-  if (saturate || j)
-    SET_ASTATREG (vs, 1);
+  if (size != 40)
+    {
+      SET_ASTATREG (v, overflow && v_i);
+      if (overflow && v_i)
+	SET_ASTATREG (vs, 1);
+    }
+
   return new_val;
 }
 
@@ -2557,7 +2565,7 @@ decode_ALU2op_0 (SIM_CPU *cpu, bu16 iw0)
   else if (opc == 2)
     {
       TRACE_INSN (cpu, "R%i <<= R%i;", dst, src);
-      SET_DREG (dst, lshift (cpu, DREG (dst), DREG (src), 32, 0));
+      SET_DREG (dst, lshift (cpu, DREG (dst), DREG (src), 32, 0, 0));
     }
   else if (opc == 3)
     {
@@ -2760,7 +2768,7 @@ decode_LOGI2op_0 (SIM_CPU *cpu, bu16 iw0)
       TRACE_INSN (cpu, "R%i <<= %s;", dst, uimm_str);
       if (INSN_LEN == 8)
 	illegal_instruction_combination (cpu);
-      SET_DREG (dst, lshift (cpu, DREG (dst), uimm, 32, 0));
+      SET_DREG (dst, lshift (cpu, DREG (dst), uimm, 32, 0, 0));
     }
 }
 
@@ -5158,7 +5166,7 @@ decode_dsp32shift_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
       if (shft <= 0)
 	val = ashiftrt (cpu, val, -shft, 16);
       else
-	val = lshift (cpu, val, shft, 16, sop == 1);
+	val = lshift (cpu, val, shft, 16, sop == 1, 1);
 
       if ((HLs & 2) == 0)
 	STORE (DREG (dst0), REG_H_L (DREG (dst0), val));
@@ -5219,7 +5227,7 @@ decode_dsp32shift_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
       if (shft <= 0)
 	val = ashiftrt (cpu, val, -shft, 40);
       else
-	val = lshift (cpu, val, shft, 40, 0);
+	val = lshift (cpu, val, shft, 40, 0, 0);
 
       STORE (AXREG (HLs), (val >> 32) & 0xff);
       STORE (AWREG (HLs), (val & 0xffffffff));
@@ -5239,7 +5247,7 @@ decode_dsp32shift_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
       if (shft <= 0)
 	val = lshiftrt (cpu, val, -shft, 40);
       else
-	val = lshift (cpu, val, shft, 40, 0);
+	val = lshift (cpu, val, shft, 40, 0, 0);
 
       STORE (AXREG (HLs), (val >> 32) & 0xff);
       STORE (AWREG (HLs), (val & 0xffffffff));
@@ -5267,9 +5275,9 @@ decode_dsp32shift_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
 	}
       else
 	{
-	  val0 = lshift (cpu, val0, shft, 16, sop == 1);
+	  val0 = lshift (cpu, val0, shft, 16, sop == 1, 1);
 	  astat = ASTAT;
-	  val1 = lshift (cpu, val1, shft, 16, sop == 1);
+	  val1 = lshift (cpu, val1, shft, 16, sop == 1, 1);
 	}
       SET_ASTAT (ASTAT | astat);
       STORE (DREG (dst0), (val1 << 16) | val0);
@@ -5294,7 +5302,7 @@ decode_dsp32shift_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
 	    STORE (DREG (dst0), ashiftrt (cpu, v, -shft, 32));
 	}
       else
-	STORE (DREG (dst0), lshift (cpu, v, shft, 32, sop == 1));
+	STORE (DREG (dst0), lshift (cpu, v, shft, 32, sop == 1, 1));
     }
   else if (sop == 3 && sopcde == 2)
     {
@@ -5330,9 +5338,9 @@ decode_dsp32shift_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
 	}
       else
 	{
-	  val0 = lshift (cpu, val0, shft, 16, 0);
+	  val0 = lshift (cpu, val0, shft, 16, 0, 0);
 	  astat = ASTAT;
-	  val1 = lshift (cpu, val1, shft, 16, 0);
+	  val1 = lshift (cpu, val1, shft, 16, 0, 0);
 	}
       SET_ASTAT (ASTAT | astat);
       STORE (DREG (dst0), (val1 << 16) | val0);
@@ -5702,7 +5710,7 @@ decode_dsp32shiftimm_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
 		      dst0, (HLs & 2) ? 'H' : 'L',
 		      src1, (HLs & 1) ? 'H' : 'L', newimmag);
 	  if (newimmag > 16)
-	    result = lshift (cpu, in, 16 - (newimmag & 0xF), 16, 0);
+	    result = lshift (cpu, in, 16 - (newimmag & 0xF), 16, 0, 1);
 	  else
 	    result = ashiftrt (cpu, in, newimmag, 16);
 	}
@@ -5711,14 +5719,14 @@ 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);
+	  result = lshift (cpu, in, immag, 16, 1, 1);
 	}
       else if (sop == 1 && bit8)
 	{
 	  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);
+	  result = lshift (cpu, in, immag, 16, 1, 1);
 	}
       else if (sop == 2 && bit8)
 	{
@@ -5732,7 +5740,7 @@ decode_dsp32shiftimm_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
 	  TRACE_INSN (cpu, "R%i.%c = R%i.%c << %i;",
 		      dst0, (HLs & 2) ? 'H' : 'L',
 		      src1, (HLs & 1) ? 'H' : 'L', immag);
-	  result = lshift (cpu, in, immag, 16, 0);
+	  result = lshift (cpu, in, immag, 16, 0, 1);
 	}
       else
 	illegal_instruction (cpu);
@@ -5820,9 +5828,9 @@ decode_dsp32shiftimm_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
       TRACE_INSN (cpu, "R%i = R%i << %i (V,S);", dst0, src1, count);
       if (count >= 0)
 	{
-	  val0 = lshift (cpu, val0, count, 16, 1);
+	  val0 = lshift (cpu, val0, count, 16, 1, 1);
 	  astat = ASTAT;
-	  val1 = lshift (cpu, val1, count, 16, 1);
+	  val1 = lshift (cpu, val1, count, 16, 1, 1);
 	}
       else
 	{
@@ -5857,9 +5865,9 @@ decode_dsp32shiftimm_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
       bu32 astat;
 
       TRACE_INSN (cpu, "R%i = R%i << %i (V);", dst0, src1, count);
-      val0 = lshift (cpu, val0, count, 16, 0);
+      val0 = lshift (cpu, val0, count, 16, 0, 1);
       astat = ASTAT;
-      val1 = lshift (cpu, val1, count, 16, 0);
+      val1 = lshift (cpu, val1, count, 16, 0, 1);
       SET_ASTAT (ASTAT | astat);
 
       STORE (DREG (dst0), val0 | (val1 << 16));
@@ -5876,9 +5884,9 @@ decode_dsp32shiftimm_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
 
       if (count & 0x10)
 	{
-	  val0 = lshift (cpu, val0, 16 - (count & 0xF), 16, 0);
+	  val0 = lshift (cpu, val0, 16 - (count & 0xF), 16, 0, 1);
 	  astat = ASTAT;
-	  val1 = lshift (cpu, val1, 16 - (count & 0xF), 16, 0);
+	  val1 = lshift (cpu, val1, 16 - (count & 0xF), 16, 0, 1);
 	}
       else
 	{
@@ -5896,7 +5904,7 @@ decode_dsp32shiftimm_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
       int count = imm6 (immag);
 
       TRACE_INSN (cpu, "R%i = R%i << %i (S);", dst0, src1, count);
-      STORE (DREG (dst0), lshift (cpu, DREG (src1), count, 32, 1));
+      STORE (DREG (dst0), lshift (cpu, DREG (src1), count, 32, 1, 1));
     }
   else if (sop == 2 && sopcde == 2)
     {
@@ -5905,7 +5913,7 @@ decode_dsp32shiftimm_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
       TRACE_INSN (cpu, "R%i = R%i >> %i;", dst0, src1, count);
 
       if (count < 0)
-	STORE (DREG (dst0), lshift (cpu, DREG (src1), -count, 32, 0));
+	STORE (DREG (dst0), lshift (cpu, DREG (src1), -count, 32, 0, 1));
       else
 	STORE (DREG (dst0), lshiftrt (cpu, DREG (src1), count, 32));
     }
@@ -5931,7 +5939,7 @@ decode_dsp32shiftimm_0 (SIM_CPU *cpu, bu16 iw0, bu16 iw1)
       TRACE_INSN (cpu, "R%i = R%i >>> %i;", dst0, src1, count);
 
       if (count < 0)
-	STORE (DREG (dst0), lshift (cpu, DREG (src1), -count, 32, 0));
+	STORE (DREG (dst0), lshift (cpu, DREG (src1), -count, 32, 0, 1));
       else
 	STORE (DREG (dst0), ashiftrt (cpu, DREG (src1), count, 32));
     }