Attachment 43068 Details for Bug 83565 – Stopgap fix

[patch] Stopgap fix

pr83565.diff (text/plain), 3.70 KB, created by Eric Botcazou on 2018-01-09 09:31:49 UTC

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Creator: Eric Botcazou

Created: 2018-01-09 09:31:49 UTC

Size: 3.70 KB

patch

obsolete

>Index: rtlanal.c
>===================================================================
>--- rtlanal.c	(revision 256275)
>+++ rtlanal.c	(working copy)
>@@ -4429,7 +4429,7 @@ nonzero_bits1 (const_rtx x, scalar_int_m
> {
>   unsigned HOST_WIDE_INT nonzero = GET_MODE_MASK (mode);
>   unsigned HOST_WIDE_INT inner_nz;
>-  enum rtx_code code;
>+  enum rtx_code code = GET_CODE (x);
>   machine_mode inner_mode;
>   unsigned int inner_width;
>   scalar_int_mode xmode;
>@@ -4465,16 +4465,16 @@ nonzero_bits1 (const_rtx x, scalar_int_m
>     return nonzero;
> 
>   /* If MODE is wider than X, but both are a single word for both the host
>-     and target machines, we can compute this from which bits of the
>-     object might be nonzero in its own mode, taking into account the fact
>-     that on many CISC machines, accessing an object in a wider mode
>-     causes the high-order bits to become undefined.  So they are
>-     not known to be zero.  */
>-
>-  if (!WORD_REGISTER_OPERATIONS
>-      && mode_width > xmode_width
>+     and target machines, we can compute this from which bits of the object
>+     might be nonzero in its own mode, taking into account the fact that, on
>+     CISC machines, accessing an object in a wider mode generally causes the
>+     high-order bits to become undefined, so they are not known to be zero.
>+     We extend this reasoning to RISC machines for rotate operations since the
>+     semantics of the operations in the larger mode is not well defined.  */
>+  if (mode_width > xmode_width
>       && xmode_width <= BITS_PER_WORD
>-      && xmode_width <= HOST_BITS_PER_WIDE_INT)
>+      && xmode_width <= HOST_BITS_PER_WIDE_INT
>+      && (!WORD_REGISTER_OPERATIONS || code == ROTATE || code == ROTATERT))
>     {
>       nonzero &= cached_nonzero_bits (x, xmode,
> 				      known_x, known_mode, known_ret);
>@@ -4484,7 +4484,6 @@ nonzero_bits1 (const_rtx x, scalar_int_m
> 
>   /* Please keep nonzero_bits_binary_arith_p above in sync with
>      the code in the switch below.  */
>-  code = GET_CODE (x);
>   switch (code)
>     {
>     case REG:
>@@ -4760,10 +4759,11 @@ nonzero_bits1 (const_rtx x, scalar_int_m
> 	}
>       break;
> 
>+    case ASHIFT:
>     case ASHIFTRT:
>     case LSHIFTRT:
>-    case ASHIFT:
>     case ROTATE:
>+    case ROTATERT:
>       /* The nonzero bits are in two classes: any bits within MODE
> 	 that aren't in xmode are always significant.  The rest of the
> 	 nonzero bits are those that are significant in the operand of
>@@ -4786,10 +4786,17 @@ nonzero_bits1 (const_rtx x, scalar_int_m
> 	  if (mode_width > xmode_width)
> 	    outer = (op_nonzero & nonzero & ~mode_mask);
> 
>-	  if (code == LSHIFTRT)
>-	    inner >>= count;
>-	  else if (code == ASHIFTRT)
>+	  switch (code)
> 	    {
>+	    case ASHIFT:
>+	      inner <<= count;
>+	      break;
>+
>+	    case LSHIFTRT:
>+	      inner >>= count;
>+	      break;
>+
>+	    case ASHIFTRT:
> 	      inner >>= count;
> 
> 	      /* If the sign bit may have been nonzero before the shift, we
>@@ -4798,13 +4805,23 @@ nonzero_bits1 (const_rtx x, scalar_int_m
> 	      if (inner & (HOST_WIDE_INT_1U << (xmode_width - 1 - count)))
> 		inner |= (((HOST_WIDE_INT_1U << count) - 1)
> 			  << (xmode_width - count));
>+	      break;
>+
>+	    case ROTATE:
>+	      inner = (inner << (count % xmode_width)
>+		       | (inner >> (xmode_width - (count % xmode_width))))
>+		      & mode_mask;
>+	      break;
>+
>+	    case ROTATERT:
>+	      inner = (inner >> (count % xmode_width)
>+		       | (inner << (xmode_width - (count % xmode_width))))
>+		      & mode_mask;
>+	      break;
>+
>+	    default:
>+	      gcc_unreachable ();
> 	    }
>-	  else if (code == ASHIFT)
>-	    inner <<= count;
>-	  else
>-	    inner = ((inner << (count % xmode_width)
>-		      | (inner >> (xmode_width - (count % xmode_width))))
>-		     & mode_mask);
> 
> 	  nonzero &= (outer | inner);
> 	}

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Attachments on bug 83565: 42959 | 42960 | 42961 | 42963 | 43068