diff options
Diffstat (limited to 'gcc/tree.c')
| -rw-r--r-- | gcc/tree.c | 19 |
1 files changed, 16 insertions, 3 deletions
@@ -1549,20 +1549,33 @@ save_expr (expr) tree expr; { tree t = fold (expr); + tree inner; /* We don't care about whether this can be used as an lvalue in this context. */ while (TREE_CODE (t) == NON_LVALUE_EXPR) t = TREE_OPERAND (t, 0); + + /* If we have simple operations applied to a SAVE_EXPR or to a SAVE_EXPR and + a constant, it will be more efficient to not make another SAVE_EXPR since + it will allow better simplification and GCSE will be able to merge the + computations if they actualy occur. */ + for (inner = t; + (TREE_CODE_CLASS (TREE_CODE (inner)) == '1' + || (TREE_CODE_CLASS (TREE_CODE (inner)) == '2' + && TREE_CONSTANT (TREE_OPERAND (inner, 1)))); + inner = TREE_OPERAND (inner, 0)) + ; + /* If the tree evaluates to a constant, then we don't want to hide that fact (i.e. this allows further folding, and direct checks for constants). However, a read-only object that has side effects cannot be bypassed. Since it is no problem to reevaluate literals, we just return the literal node. */ - - if (TREE_CONSTANT (t) || (TREE_READONLY (t) && ! TREE_SIDE_EFFECTS (t)) - || TREE_CODE (t) == SAVE_EXPR || TREE_CODE (t) == ERROR_MARK) + if (TREE_CONSTANT (inner) + || (TREE_READONLY (inner) && ! TREE_SIDE_EFFECTS (inner)) + || TREE_CODE (inner) == SAVE_EXPR || TREE_CODE (inner) == ERROR_MARK) return t; /* If T contains a PLACEHOLDER_EXPR, we must evaluate it each time, since |