feb75e4643
We have long had the fold:
/* Pattern match
tem = (sizetype) ptr;
tem = tem & algn;
tem = -tem;
... = ptr p+ tem;
and produce the simpler and easier to analyze with respect to alignment
... = ptr & ~algn; */
But the gimple in gcc.target/aarch64/sve/pr98119.c has a variant in
which a constant is added before the conversion, giving:
tem = (sizetype) (ptr p+ CST);
tem = tem & algn;
tem = -tem;
... = ptr p+ tem;
This case is also valid if algn fits within the trailing zero bits
of CST. Adding CST then has no effect.
Similarly the testcase has:
tem = (sizetype) (ptr p+ CST1);
tem = tem & algn;
tem = CST2 - tem;
... = ptr p+ tem;
This folds to:
... = (ptr & ~algn) p+ CST2;
if algn fits within the trailing zero bits of both CST1 and CST2.
An alternative would be:
... = (ptr p+ CST2) & ~algn;
but I would expect the alignment to be more easily shareable than
the CST2 addition, given that the CST2 addition wasn't being applied
by a POINTER_PLUS_EXPR.
gcc/
* match.pd: Extend pointer alignment folds so that they handle
the case where a constant is added before or after the alignment.
gcc/testsuite/
* gcc.dg/pointer-arith-11.c: New test.
* gcc.dg/pointer-arith-12.c: Likewise.
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