From 33f86e263dda7b4406fb53e2b9c3faed372aa340 Mon Sep 17 00:00:00 2001 From: niklas Date: Sat, 30 Mar 1996 14:25:42 +0000 Subject: [PATCH] From NetBSD: Patch from J"orn Rennecke that fixes code generation bugs with long long comparisons. As of this date, this change hasn't made it into the development sources. We must consider this when it comes time to integrate a newer gcc release. Thu Mar 7 01:16:23 1996 J"orn Rennecke (amylaar@meolyon.hanse.de) * expmed.c (negate_rtx): Don't negate LONG_MIN if mode is wider than HOST_WIDE_INT. gcc now produces worse code for this test case than gcc 2.5.8 when invoked with -O , but it will optimize as good as gcc 2.5.8 (i.e. all comparisons vanish) when invoked with -O2 , thus I think it doesn't matter. If anyone is interested in looking into this, the code in expr.c, function expand_expr, case MINUS_EXPR, if-clause for if (TREE_UNSIGNED (type) || TREE_OVERFLOW (negated)), will refuse to convert the subtraction into an addition if there is an overflow in the conversion or negation of the constant. If both host and target machine are binary computers with 2-complement representation, the overflow should not matter. --- gnu/usr.bin/gcc/expmed.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/gnu/usr.bin/gcc/expmed.c b/gnu/usr.bin/gcc/expmed.c index 8006e8be954..83c77e6f131 100644 --- a/gnu/usr.bin/gcc/expmed.c +++ b/gnu/usr.bin/gcc/expmed.c @@ -188,6 +188,9 @@ negate_rtx (mode, x) if (GET_CODE (x) == CONST_INT) { HOST_WIDE_INT val = - INTVAL (x); + if (GET_MODE_BITSIZE (mode) > HOST_BITS_PER_WIDE_INT + && INTVAL (x) < 0 && val < 0) + return expand_unop (mode, neg_optab, x, NULL_RTX, 0); if (GET_MODE_BITSIZE (mode) < HOST_BITS_PER_WIDE_INT) { /* Sign extend the value from the bits that are significant. */ -- 2.20.1