Re: [PATCH 1/2]middle-end: Fix wrong overmatching of div-bitmask by using new optabs [PR108583]

[Andrew MacLeod <amacleod@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 4346 bytes --]


On 2/23/23 03:36, Tamar Christina wrote:
> Hi Andrew,
>
>>>> Oh yeah, and in case you haven't figured it out on your own, you'll
>>>> have to remove WIDEN_MULT_EXPR from the range-ops init table.   This
>>>> non-standard mechanism only gets checked if there is no standard
>>>> range-op table entry for the tree code :-P
>>>>
>>> Hmm it looks like it'll work, but it keeps segfaulting in:
>>>
>>> bool
>>> range_op_handler::fold_range (vrange &r, tree type,
>>> 			      const vrange &lh,
>>> 			      const vrange &rh,
>>> 			      relation_trio rel) const
>>> {
>>>     gcc_checking_assert (m_valid);
>>>     if (m_int)
>>>       return m_int->fold_range (as_a <irange> (r), type,
>>> 			   as_a <irange> (lh),
>>> 			   as_a <irange> (rh), rel);
>>>
>>> while trying to call fold_range.
>>>
>>> But m_int is set to the right instance. Probably something I'm
>>> missing, I'll double check it all.
>>>
>> Hmm.  whats your class operator_widen_mult* look like? what are you
>> inheriting from?   Send me your patch and I'll have a look if you want. this is
>> somewhat  new territory :-)
> I've attached the patch, and my testcase is:
>
> int decMultiplyOp_zacc, decMultiplyOp_iacc;
> int *decMultiplyOp_lp;
> void decMultiplyOp() {
>    decMultiplyOp_lp = &decMultiplyOp_zacc;
>    for (; decMultiplyOp_lp < &decMultiplyOp_zacc + decMultiplyOp_iacc;
>         decMultiplyOp_lp++)
>      *decMultiplyOp_lp = 0;
> }
>
> And compiling with aarch64-none-elf-gcc -O2 zero.c -S -o - -Werror=stringop-overflow
>
> Also to explain a bit on why we're only seeing this now:
>
> The original sequence for most of the pipeline is based on a cast and multiplication
>
>    # RANGE [irange] long unsigned int [0, 2147483647][18446744071562067968, +INF]
>    _14 = (long unsigned intD.11) decMultiplyOp_iacc.2_13;
>    # RANGE [irange] long unsigned int [0, 8589934588][18446744065119617024, 18446744073709551612] NONZERO 0xfffffffffffffffc
>    _15 = _14 * 4;
>
> But things like widening multiply are quite common, so some ISAs have it on scalars as well, not just vectors.
> So there's a pass widening_mul that runs late for these targets.  This replaces the above with
>
>    # RANGE [irange] long unsigned int [0, 8589934588][18446744065119617024, 18446744073709551612] NONZERO 0xfffffffffffffffc
>    _15 = decMultiplyOp_iacc.2_13 w* 4;
>
> And copies over the final range from the original expression.
>
> After that there are passes like the warning passes that try to requery ranged to see if any optimization  has changed them.
> Before my attempt to support *w this would just return VARYING and it would only use the old range.
>
> Now however, without taking care to sign extend when appropriate the MIN range changes from a negative value to a large
> positive one when we increase the precision.  So passes that re-query late get the wrong range.  That's why for instance in this case
> we get an incorrect warning generated.
>
> Thanks for the help!
>
> Tamar
>
>> I cant imagine it being a linkage thing between the 2 files since the operator is
>> defined in another file and the address taken in this one?
>> that should work, but strange that cant make the call...
>>
>> Andrew

It is some sort of linkage/vtable thing.  The fix.diff patch applied on 
top of what you have will fix the fold issue. This'll do for now until I 
formalize how this is going to work goign forward.

Inheriting from operator_mult is also going to be hazardous because it 
also has an op1_range and op2_range...  you should at least define those 
and return VARYING to avoid other issues.  Same thing applies to 
widen_plus I think, and it has relation processing and other things as 
well.  Your widen operands are not what those classes expect, so I think 
you probably just want a fresh range operator.

It also looks like the mult operation is sign/zero extending both upper 
bounds, and neither lower bound..   I think that should be the LH upper 
and lower bound?

I've attached a second patch  (newversion.patch) which incorporates my 
fix, the fix to the sign of only op1's bounds,  as well as a 
simplification of the classes to not inherit from operator_mult/plus..   
I think this still does what you want?  and it wont get you into 
unexpected trouble later :-)

let me know if this is still doing what you are expecting...

Andrew


[-- Attachment #2: fix.diff --]
[-- Type: text/x-patch, Size: 1825 bytes --]

diff --git a/gcc/gimple-range-op.cc b/gcc/gimple-range-op.cc
index 81089876d30..824e0338f34 100644
--- a/gcc/gimple-range-op.cc
+++ b/gcc/gimple-range-op.cc
@@ -777,8 +777,6 @@ gimple_range_op_handler::maybe_non_standard ()
       {
 	case WIDEN_MULT_EXPR:
 	{
-	  extern class range_operator &op_widen_mult_signed;
-	  extern class range_operator &op_widen_mult_unsigned;
 	  m_valid = true;
 	  m_op1 = gimple_assign_rhs1 (m_stmt);
 	  m_op2 = gimple_assign_rhs2 (m_stmt);
@@ -788,9 +786,9 @@ gimple_range_op_handler::maybe_non_standard ()
 	    std::swap (m_op1, m_op2);
 
 	  if (signed1 || signed2)
-	    m_int = &op_widen_mult_signed;
+	    m_int = ptr_op_widen_mult_signed;
 	  else
-	    m_int = &op_widen_mult_unsigned;
+	    m_int = ptr_op_widen_mult_unsigned;
 	  break;
 	}
 	default:
diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index c15bd83b077..bace915b256 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -2072,6 +2072,7 @@ public:
 				const wide_int &w0, const wide_int &w1)
     const;
 } op_widen_mult_signed;
+range_operator *ptr_op_widen_mult_signed = &op_widen_mult_signed;
 
 void
 operator_widen_mult_signed::wi_fold (irange &r, tree type,
@@ -2119,6 +2120,7 @@ public:
 				const wide_int &w0, const wide_int &w1)
     const;
 } op_widen_mult_unsigned;
+range_operator *ptr_op_widen_mult_unsigned = &op_widen_mult_unsigned;
 
 void
 operator_widen_mult_unsigned::wi_fold (irange &r, tree type,
diff --git a/gcc/range-op.h b/gcc/range-op.h
index f00b747f08a..5fe463234ae 100644
--- a/gcc/range-op.h
+++ b/gcc/range-op.h
@@ -311,4 +311,6 @@ private:
 // This holds the range op table for floating point operations.
 extern floating_op_table *floating_tree_table;
 
+extern range_operator *ptr_op_widen_mult_signed;
+extern range_operator *ptr_op_widen_mult_unsigned;
 #endif // GCC_RANGE_OP_H

[-- Attachment #3: newversion.patch --]
[-- Type: text/x-patch, Size: 6125 bytes --]

diff --git a/gcc/gimple-range-op.cc b/gcc/gimple-range-op.cc
index d9dfdc56939..824e0338f34 100644
--- a/gcc/gimple-range-op.cc
+++ b/gcc/gimple-range-op.cc
@@ -179,6 +179,8 @@ gimple_range_op_handler::gimple_range_op_handler (gimple *s)
   // statements.
   if (is_a <gcall *> (m_stmt))
     maybe_builtin_call ();
+  else
+    maybe_non_standard ();
 }
 
 // Calculate what we can determine of the range of this unary
@@ -764,6 +766,36 @@ public:
   }
 } op_cfn_parity;
 
+// Set up a gimple_range_op_handler for any nonstandard function which can be
+// supported via range-ops.
+
+void
+gimple_range_op_handler::maybe_non_standard ()
+{
+  if (gimple_code (m_stmt) == GIMPLE_ASSIGN)
+    switch (gimple_assign_rhs_code (m_stmt))
+      {
+	case WIDEN_MULT_EXPR:
+	{
+	  m_valid = true;
+	  m_op1 = gimple_assign_rhs1 (m_stmt);
+	  m_op2 = gimple_assign_rhs2 (m_stmt);
+	  bool signed1 = TYPE_SIGN (TREE_TYPE (m_op1)) == SIGNED;
+	  bool signed2 = TYPE_SIGN (TREE_TYPE (m_op2)) == SIGNED;
+	  if (signed2 && !signed1)
+	    std::swap (m_op1, m_op2);
+
+	  if (signed1 || signed2)
+	    m_int = ptr_op_widen_mult_signed;
+	  else
+	    m_int = ptr_op_widen_mult_unsigned;
+	  break;
+	}
+	default:
+	  break;
+      }
+}
+
 // Set up a gimple_range_op_handler for any built in function which can be
 // supported via range-ops.
 
diff --git a/gcc/gimple-range-op.h b/gcc/gimple-range-op.h
index 743b858126e..1bf63c5ce6f 100644
--- a/gcc/gimple-range-op.h
+++ b/gcc/gimple-range-op.h
@@ -41,6 +41,7 @@ public:
 		 relation_trio = TRIO_VARYING);
 private:
   void maybe_builtin_call ();
+  void maybe_non_standard ();
   gimple *m_stmt;
   tree m_op1, m_op2;
 };
diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 5c67bce6d3a..7cd19a92d00 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -1556,6 +1556,34 @@ operator_plus::op2_range (irange &r, tree type,
   return op1_range (r, type, lhs, op1, rel.swap_op1_op2 ());
 }
 
+class operator_widen_plus : public range_operator
+{
+public:
+  virtual void wi_fold (irange &r, tree type,
+			const wide_int &lh_lb,
+			const wide_int &lh_ub,
+			const wide_int &rh_lb,
+			const wide_int &rh_ub) const;
+} op_widen_plus;
+
+void
+operator_widen_plus::wi_fold (irange &r, tree type,
+			const wide_int &lh_lb, const wide_int &lh_ub,
+			const wide_int &rh_lb, const wide_int &rh_ub) const
+{
+   wi::overflow_type ov_lb, ov_ub;
+   signop s = TYPE_SIGN (type);
+
+   wide_int lh_wlb = wide_int::from (lh_lb, wi::get_precision (lh_lb) * 2, s);
+   wide_int rh_wlb = wide_int::from (rh_lb, wi::get_precision (rh_lb) * 2, s);
+   wide_int lh_wub = wide_int::from (lh_ub, wi::get_precision (lh_ub) * 2, s);
+   wide_int rh_wub = wide_int::from (rh_ub, wi::get_precision (rh_ub) * 2, s);
+
+   wide_int new_lb = wi::add (lh_wlb, rh_wlb, s, &ov_lb);
+   wide_int new_ub = wi::add (lh_wub, rh_wub, s, &ov_ub);
+
+   r = int_range<2> (type, new_lb, new_ub);
+}
 
 class operator_minus : public range_operator
 {
@@ -2031,6 +2059,70 @@ operator_mult::wi_fold (irange &r, tree type,
     }
 }
 
+class operator_widen_mult_signed : public range_operator
+{
+public:
+  virtual void wi_fold (irange &r, tree type,
+			const wide_int &lh_lb,
+			const wide_int &lh_ub,
+			const wide_int &rh_lb,
+			const wide_int &rh_ub)
+    const;
+} op_widen_mult_signed;
+range_operator *ptr_op_widen_mult_signed = &op_widen_mult_signed;
+
+void
+operator_widen_mult_signed::wi_fold (irange &r, tree type,
+				     const wide_int &lh_lb,
+				     const wide_int &lh_ub,
+				     const wide_int &rh_lb,
+				     const wide_int &rh_ub) const
+{
+  signop s = TYPE_SIGN (type);
+
+  wide_int lh_wlb = wide_int::from (lh_lb, wi::get_precision (lh_lb) * 2, SIGNED);
+  wide_int lh_wub = wide_int::from (lh_ub, wi::get_precision (lh_ub) * 2, SIGNED);
+  wide_int rh_wlb = wide_int::from (rh_lb, wi::get_precision (rh_lb) * 2, s);
+  wide_int rh_wub = wide_int::from (rh_ub, wi::get_precision (rh_ub) * 2, s);
+
+  /* We don't expect a widening multiplication to be able to overflow but range
+     calculations for multiplications are complicated.  After widening the
+     operands lets call the base class.  */
+  return op_mult.wi_fold (r, type, lh_wlb, lh_wub, rh_wlb, rh_wub);
+}
+
+
+class operator_widen_mult_unsigned : public range_operator
+{
+public:
+  virtual void wi_fold (irange &r, tree type,
+			const wide_int &lh_lb,
+			const wide_int &lh_ub,
+			const wide_int &rh_lb,
+			const wide_int &rh_ub)
+    const;
+} op_widen_mult_unsigned;
+range_operator *ptr_op_widen_mult_unsigned = &op_widen_mult_unsigned;
+
+void
+operator_widen_mult_unsigned::wi_fold (irange &r, tree type,
+				       const wide_int &lh_lb,
+				       const wide_int &lh_ub,
+				       const wide_int &rh_lb,
+				       const wide_int &rh_ub) const
+{
+  signop s = TYPE_SIGN (type);
+
+  wide_int lh_wlb = wide_int::from (lh_lb, wi::get_precision (lh_lb) * 2, UNSIGNED);
+  wide_int lh_wub = wide_int::from (lh_ub, wi::get_precision (lh_ub) * 2, UNSIGNED);
+  wide_int rh_wlb = wide_int::from (rh_lb, wi::get_precision (rh_lb) * 2, s);
+  wide_int rh_wub = wide_int::from (rh_ub, wi::get_precision (rh_ub) * 2, s);
+
+  /* We don't expect a widening multiplication to be able to overflow but range
+     calculations for multiplications are complicated.  After widening the
+     operands lets call the base class.  */
+  return op_mult.wi_fold (r, type, lh_wlb, lh_wub, rh_wlb, rh_wub);
+}
 
 class operator_div : public cross_product_operator
 {
@@ -4473,6 +4565,7 @@ integral_table::integral_table ()
   set (GT_EXPR, op_gt);
   set (GE_EXPR, op_ge);
   set (PLUS_EXPR, op_plus);
+  set (WIDEN_PLUS_EXPR, op_widen_plus);
   set (MINUS_EXPR, op_minus);
   set (MIN_EXPR, op_min);
   set (MAX_EXPR, op_max);
diff --git a/gcc/range-op.h b/gcc/range-op.h
index f00b747f08a..5fe463234ae 100644
--- a/gcc/range-op.h
+++ b/gcc/range-op.h
@@ -311,4 +311,6 @@ private:
 // This holds the range op table for floating point operations.
 extern floating_op_table *floating_tree_table;
 
+extern range_operator *ptr_op_widen_mult_signed;
+extern range_operator *ptr_op_widen_mult_unsigned;
 #endif // GCC_RANGE_OP_H