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Re: Move some bit and binary optimizations in simplify and match

On Wed, 14 Oct 2015, Richard Biener wrote:


+/* Fold (a * (1 << b)) into (a << b)  */
+(simplify
+ (mult:c @0 (convert? (lshift integer_onep@1 @2)))
+  (if (! FLOAT_TYPE_P (type)
+        && tree_nop_conversion_p (type, TREE_TYPE (@2)))
+   (lshift @0 (convert @2))))

You don't need/want to convert @2 (fold-const doesn't convert, does it?),
and you don't need to check for tree_nop_conversion_p.


I think for long x and x * (long)(1u << b) you need to do because the
result for b == 33 would be different.


- that check should be with TREE_TYPE (@1)
- 1u << 33 is undefined, isn't it?
x * (int)(1ul << b), which for b=33 should yield 0, would give the undefined x << b so some check does seem needed indeed. 

--
Marc Glisse
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