diff --git a/gcc/testsuite/gcc.dg/wmul-1.c b/gcc/testsuite/gcc.dg/wmul-1.c new file mode 100644 index 0000000..3e762f4 --- /dev/null +++ b/gcc/testsuite/gcc.dg/wmul-1.c @@ -0,0 +1,19 @@ +/* Not to fuse widening multiply with accumulate if the multiply has more than + one uses. + Note that for targets where pointer and int are of the same size or + widening multiply-and-accumulate is not available, this test just passes. */ + +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-widening_mul" } */ + +typedef int ArrT [10][10]; + +void +foo (ArrT Arr, int Idx) +{ + Arr[Idx][Idx] = 1; + Arr[Idx + 10][Idx] = 2; +} + +/* { dg-final { scan-tree-dump-not "WIDEN_MULT_PLUS_EXPR" "widening_mul" } } */ +/* { dg-final { cleanup-tree-dump "widening_mul" } } */ diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c index f7f8ec9..77701ae 100644 --- a/gcc/tree-ssa-math-opts.c +++ b/gcc/tree-ssa-math-opts.c @@ -2425,20 +2425,25 @@ convert_plusminus_to_widen (gimple_stmt_iterator *gsi, gimple stmt, It might also appear that it would be sufficient to use the existing operands of the widening multiply, but that would limit the choice of - multiply-and-accumulate instructions. */ + multiply-and-accumulate instructions. + + If the widened-multiplication result has more than one uses, it is + probably wiser not to do the conversion. */ if (code == PLUS_EXPR && (rhs1_code == MULT_EXPR || rhs1_code == WIDEN_MULT_EXPR)) { - if (!is_widening_mult_p (rhs1_stmt, &type1, &mult_rhs1, - &type2, &mult_rhs2)) + if (!has_single_use (rhs1) + || !is_widening_mult_p (rhs1_stmt, &type1, &mult_rhs1, + &type2, &mult_rhs2)) return false; add_rhs = rhs2; conv_stmt = conv1_stmt; } else if (rhs2_code == MULT_EXPR || rhs2_code == WIDEN_MULT_EXPR) { - if (!is_widening_mult_p (rhs2_stmt, &type1, &mult_rhs1, - &type2, &mult_rhs2)) + if (!has_single_use (rhs2) + || !is_widening_mult_p (rhs2_stmt, &type1, &mult_rhs1, + &type2, &mult_rhs2)) return false; add_rhs = rhs1; conv_stmt = conv2_stmt;