[Committed] PR middle-end/102029: Stricter typing in LSHIFT_EXPR sign folding.

[Committed] PR middle-end/102029: Stricter typing in LSHIFT_EXPR sign folding.

[Roger Sayle]

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My sincere apologies to everyone (again).  As diagnosed by
Jakub Jelinek, my recent patch to fold the signedness of LSHIFT_EXPR
needs to be careful not to attempt transforming a left shift in an
integer type into an invalid left shift of a pointer type.

This patch has been committed as obvious, after testing that a
"make bootstrap" on x86_64-pc-linux-gnu is unaffected [make -k check
is underway].

Sorry (yet) again.


2021-08-23  Roger Sayle  <roger@nextmovesoftware.com>
	    Jakub Jelinek  <jakub@redhat.com>

gcc/ChangeLog
	PR middle-end/102029
	* match.pd (shift transformations): Add an additional check for
	!POINTER_TYPE_P in the recently added left shift transformation.

gcc/testsuite/ChangeLog
	PR middle-end/102029
	* gcc.dg/fold-convlshift-3.c: New test case.

Roger
--


[-- Attachment #2: patch.txt --]
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diff --git a/gcc/match.pd b/gcc/match.pd
index 978a1b0..e5bbb12 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3389,7 +3389,9 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
    the form that minimizes the number of conversions.  */
 (simplify
  (convert (lshift:s@0 (convert:s@1 @2) INTEGER_CST@3))
- (if (tree_nop_conversion_p (type, TREE_TYPE (@0))
+ (if (INTEGRAL_TYPE_P (type)
+      && !POINTER_TYPE_P (type)
+      && tree_nop_conversion_p (type, TREE_TYPE (@0))
       && INTEGRAL_TYPE_P (TREE_TYPE (@2))
       && TYPE_PRECISION (TREE_TYPE (@2)) <= TYPE_PRECISION (type))
   (lshift (convert @2) @3)))

[-- Attachment #3: fold-convlshift-3.c --]
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/* PR middle-end/102029 */
/* { dg-do compile } */
/* { dg-options "-O2" } */
int *
foo (const __PTRDIFF_TYPE__ l)
{
  return (int *) (l << 2);
}