From cef158f9253739ab1b1f4342d530b933f1e1fc34 Mon Sep 17 00:00:00 2001 From: Richard Guenther Date: Wed, 7 Jan 2009 10:53:30 +0000 Subject: [PATCH] re PR middle-end/38751 (odd performance regression with -Os) 2009-01-07 Richard Guenther PR middle-end/38751 * fold-const.c (extract_muldiv): Remove obsolete comment. (fold_plusminus_mult_expr): Undo MINUS_EXPR to PLUS_EXPR canonicalization for the canonicalization. From-SVN: r143152 --- gcc/ChangeLog | 7 +++++++ gcc/fold-const.c | 16 +++++++++++----- 2 files changed, 18 insertions(+), 5 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index a8a606a..81804116 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,10 @@ +2009-01-07 Richard Guenther + + PR middle-end/38751 + * fold-const.c (extract_muldiv): Remove obsolete comment. + (fold_plusminus_mult_expr): Undo MINUS_EXPR + to PLUS_EXPR canonicalization for the canonicalization. + 2009-01-07 Gerald Pfeifer * doc/install.texi (alpha*-dec-osf*): Remove note on 32-bit diff --git a/gcc/fold-const.c b/gcc/fold-const.c index be542b7..9b4106b 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -6008,10 +6008,6 @@ optimize_minmax_comparison (enum tree_code code, tree type, tree op0, tree op1) expression would not overflow or that overflow is undefined for the type in the language in question. - We also canonicalize (X + 7) * 4 into X * 4 + 28 in the hope that either - the machine has a multiply-accumulate insn or that this is part of an - addressing calculation. - If we return a non-null expression, it is an equivalent form of the original computation, but need not be in the original type. @@ -7439,7 +7435,17 @@ fold_plusminus_mult_expr (enum tree_code code, tree type, tree arg0, tree arg1) else if (TREE_CODE (arg1) == INTEGER_CST) { arg10 = build_one_cst (type); - arg11 = arg1; + /* As we canonicalize A - 2 to A + -2 get rid of that sign for + the purpose of this canonicalization. */ + if (TREE_INT_CST_HIGH (arg1) == -1 + && negate_expr_p (arg1) + && code == PLUS_EXPR) + { + arg11 = negate_expr (arg1); + code = MINUS_EXPR; + } + else + arg11 = arg1; } else { -- 2.7.4