On Thu, 13 Jul 2017, Marc Glisse wrote: > I notice that we do not turn (X*10)*10 into X*100 in GIMPLE [...]
I've completely missed that. Posting another patch to address that. > Relying on inner expressions being folded can be slightly dangerous, > especially for generic IIRC. It seems easy enough to check that @1 is neither > 0 nor -1 for safety. Yep - done. > Probably needs :s on the inner multiplication. Not 100% sure, but done in this version. > Unless the test on TYPE_OVERFLOW_SANITIZED etc is shared with adjacent > transformations, I'd rather put it inside, with the other if, but that's a > matter of taste. Done, probably better that way. > One small testcase please? Or is there already one that is currently failing? No, I'm not aware of any preexisting testcase. Added. * match.pd ((X * CST) * Y): Reassociate to (X * Y) * CST. testsuite/ * gcc.dg/tree-ssa/assoc-2.c: New testcase. diff --git a/gcc/match.pd b/gcc/match.pd index 4c64b21..36045f1 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -2139,6 +2139,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (mult @0 integer_minus_onep) (negate @0)) +/* Reassociate (X * CST) * Y to (X * Y) * CST. This does not introduce + signed overflow for CST != 0 && CST != -1. */ +(simplify + (mult:c (mult:s @0 INTEGER_CST@1) @2) + (if (TREE_CODE (@2) != INTEGER_CST + && !integer_zerop (@1) && !integer_minus_onep (@1) + && !TYPE_OVERFLOW_SANITIZED (type) && !TYPE_SATURATING (type)) + (mult (mult @0 @2) @1))) + /* True if we can easily extract the real and imaginary parts of a complex number. */ (match compositional_complex diff --git a/gcc/testsuite/gcc.dg/tree-ssa/assoc-2.c b/gcc/testsuite/gcc.dg/tree-ssa/assoc-2.c new file mode 100644 index 0000000..a92c882 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/assoc-2.c @@ -0,0 +1,8 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-gimple-raw -fdump-tree-optimized-raw" } */ + +int f0(int a, int b){ + return a * 33 * b * 55; +} + +/* { dg-final { scan-tree-dump-times "mult_expr" 2 "gimple" } } */