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Re: [wide-int 5/8] Use LOG2_BITS_PER_UNIT

From: Kenneth Zadeck <zadeck at naturalbridge dot com>
To: gcc-patches at gcc dot gnu dot org, mikestump at comcast dot net, rdsandiford at googlemail dot com
Date: Tue, 22 Apr 2014 16:31:32 -0400
Subject: Re: [wide-int 5/8] Use LOG2_BITS_PER_UNIT
Authentication-results: sourceware.org; auth=none
References: <87r44pdtfn dot fsf at talisman dot default>



On 04/22/2014 04:02 PM, Richard Sandiford wrote:

Looks like a few uses of the old idiom:

   BITS_PER_UNIT == 8 ? 3 : exact_log2 (BITS_PER_UNIT)

I do not think that these crept in as much as they were never squished out.

have crept in.  This patch replaces them with LOG2_BITS_PER_UNIT.

Tested on x86_64-linux-gnu.  OK to install?

Thanks,
Richard


Index: gcc/expr.c
===================================================================
--- gcc/expr.c	2014-04-22 20:58:26.969683484 +0100
+++ gcc/expr.c	2014-04-22 21:00:26.377614881 +0100
@@ -6801,8 +6801,7 @@ get_inner_reference (tree exp, HOST_WIDE
  	      if (!integer_zerop (off))
  		{
  		  offset_int boff, coff = mem_ref_offset (exp);
-		  boff = wi::lshift (coff, (BITS_PER_UNIT == 8
-					    ? 3 : exact_log2 (BITS_PER_UNIT)));
+		  boff = wi::lshift (coff, LOG2_BITS_PER_UNIT);
  		  bit_offset += boff;
  		}
  	      exp = TREE_OPERAND (TREE_OPERAND (exp, 0), 0);
@@ -6828,8 +6827,7 @@ get_inner_reference (tree exp, HOST_WIDE
      {
        offset_int tem = wi::sext (wi::to_offset (offset),
  				 TYPE_PRECISION (sizetype));
-      tem = wi::lshift (tem, (BITS_PER_UNIT == 8
-			      ? 3 : exact_log2 (BITS_PER_UNIT)));
+      tem = wi::lshift (tem, LOG2_BITS_PER_UNIT);
        tem += bit_offset;
        if (wi::fits_shwi_p (tem))
  	{
@@ -6844,16 +6842,12 @@ get_inner_reference (tree exp, HOST_WIDE
        /* Avoid returning a negative bitpos as this may wreak havoc later.  */
        if (wi::neg_p (bit_offset))
          {
-	  offset_int mask
-	    = wi::mask <offset_int> (BITS_PER_UNIT == 8
-				     ? 3 : exact_log2 (BITS_PER_UNIT),
-				     false);
+	  offset_int mask = wi::mask <offset_int> (LOG2_BITS_PER_UNIT, false);
  	  offset_int tem = bit_offset.and_not (mask);
  	  /* TEM is the bitpos rounded to BITS_PER_UNIT towards -Inf.
  	     Subtract it to BIT_OFFSET and add it (scaled) to OFFSET.  */
  	  bit_offset -= tem;
-	  tem = wi::arshift (tem, (BITS_PER_UNIT == 8
-				   ? 3 : exact_log2 (BITS_PER_UNIT)));
+	  tem = wi::arshift (tem, LOG2_BITS_PER_UNIT);
  	  offset = size_binop (PLUS_EXPR, offset,
  			       wide_int_to_tree (sizetype, tem));
  	}
Index: gcc/tree-dfa.c
===================================================================
--- gcc/tree-dfa.c	2014-04-22 20:58:27.020683881 +0100
+++ gcc/tree-dfa.c	2014-04-22 21:00:26.378614888 +0100
@@ -463,10 +463,7 @@ get_ref_base_and_extent (tree exp, HOST_
  			  {
  			    offset_int tem = (wi::to_offset (ssize)
  					      - wi::to_offset (fsize));
-			    if (BITS_PER_UNIT == 8)
-			      tem = wi::lshift (tem, 3);
-			    else
-			      tem *= BITS_PER_UNIT;
+			    tem = wi::lshift (tem, LOG2_BITS_PER_UNIT);
  			    tem -= woffset;
  			    maxsize += tem;
  			  }
@@ -583,8 +580,7 @@ get_ref_base_and_extent (tree exp, HOST_
  	      else
  		{
  		  offset_int off = mem_ref_offset (exp);
-		  off = wi::lshift (off, (BITS_PER_UNIT == 8
-					  ? 3 : exact_log2 (BITS_PER_UNIT)));
+		  off = wi::lshift (off, LOG2_BITS_PER_UNIT);
  		  off += bit_offset;
  		  if (wi::fits_shwi_p (off))
  		    {
Index: gcc/tree-ssa-alias.c
===================================================================
--- gcc/tree-ssa-alias.c	2014-04-22 20:58:26.969683484 +0100
+++ gcc/tree-ssa-alias.c	2014-04-22 21:00:26.378614888 +0100
@@ -1041,8 +1041,7 @@ indirect_ref_may_alias_decl_p (tree ref1
    /* The offset embedded in MEM_REFs can be negative.  Bias them
       so that the resulting offset adjustment is positive.  */
    offset_int moff = mem_ref_offset (base1);
-  moff = wi::lshift (moff, (BITS_PER_UNIT == 8
-			    ? 3 : exact_log2 (BITS_PER_UNIT)));
+  moff = wi::lshift (moff, LOG2_BITS_PER_UNIT);
    if (wi::neg_p (moff))
      offset2p += (-moff).to_short_addr ();
    else
@@ -1118,8 +1117,7 @@ indirect_ref_may_alias_decl_p (tree ref1
        || TREE_CODE (dbase2) == TARGET_MEM_REF)
      {
        offset_int moff = mem_ref_offset (dbase2);
-      moff = wi::lshift (moff, (BITS_PER_UNIT == 8
-				? 3 : exact_log2 (BITS_PER_UNIT)));
+      moff = wi::lshift (moff, LOG2_BITS_PER_UNIT);
        if (wi::neg_p (moff))
  	doffset1 -= (-moff).to_short_addr ();
        else
@@ -1217,15 +1215,13 @@ indirect_refs_may_alias_p (tree ref1 ATT
        /* The offset embedded in MEM_REFs can be negative.  Bias them
  	 so that the resulting offset adjustment is positive.  */
        moff = mem_ref_offset (base1);
-      moff = wi::lshift (moff, (BITS_PER_UNIT == 8
-				? 3 : exact_log2 (BITS_PER_UNIT)));
+      moff = wi::lshift (moff, LOG2_BITS_PER_UNIT);
        if (wi::neg_p (moff))
  	offset2 += (-moff).to_short_addr ();
        else
  	offset1 += moff.to_shwi ();
        moff = mem_ref_offset (base2);
-      moff = wi::lshift (moff, (BITS_PER_UNIT == 8
-				? 3 : exact_log2 (BITS_PER_UNIT)));
+      moff = wi::lshift (moff, LOG2_BITS_PER_UNIT);
        if (wi::neg_p (moff))
  	offset1 += (-moff).to_short_addr ();
        else
@@ -2200,12 +2196,10 @@ stmt_kills_ref_p_1 (gimple stmt, ao_ref
  				       TREE_OPERAND (ref->base, 1)))
  		{
  		  offset_int off1 = mem_ref_offset (base);
-		  off1 = wi::lshift (off1, (BITS_PER_UNIT == 8
-					    ? 3 : exact_log2 (BITS_PER_UNIT)));
+		  off1 = wi::lshift (off1, LOG2_BITS_PER_UNIT);
  		  off1 += offset;
  		  offset_int off2 = mem_ref_offset (ref->base);
-		  off2 = wi::lshift (off2, (BITS_PER_UNIT == 8
-					    ? 3 : exact_log2 (BITS_PER_UNIT)));
+		  off2 = wi::lshift (off2, LOG2_BITS_PER_UNIT);
  		  off2 += ref_offset;
  		  if (wi::fits_shwi_p (off1) && wi::fits_shwi_p (off2))
  		    {
Index: gcc/tree-ssa-sccvn.c
===================================================================
--- gcc/tree-ssa-sccvn.c	2014-04-22 20:58:26.969683484 +0100
+++ gcc/tree-ssa-sccvn.c	2014-04-22 21:00:26.378614888 +0100
@@ -817,8 +817,7 @@ copy_reference_ops_from_ref (tree ref, v
  		    offset_int off
  		      = (wi::to_offset (this_offset)
  			 + wi::lrshift (wi::to_offset (bit_offset),
-					BITS_PER_UNIT == 8
-					? 3 : exact_log2 (BITS_PER_UNIT)));
+					LOG2_BITS_PER_UNIT));
  		    if (wi::fits_shwi_p (off)
  			/* Probibit value-numbering zero offset components
  			   of addresses the same before the pass folding

References:
- [wide-int 5/8] Use LOG2_BITS_PER_UNIT
  - From: Richard Sandiford

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