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[Bug c/29274] New: 4.1, 4.2 (possibly 4.0?) not using mulsidi3
- From: "eplondke at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 28 Sep 2006 16:42:55 -0000
- Subject: [Bug c/29274] New: 4.1, 4.2 (possibly 4.0?) not using mulsidi3
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
GCC 4.x tree optimization decides to put int values into long long int
temporaries. When RTL expansion comes around, the expander sees only a DImode
multiply and so generates three SImode multiplies to deal with the problem.
GCC 3.x sees that the source values are SImode and uses mulsidi3 to generate
32x32->64 multiplies, which are much more efficient. It also picks up the
accumulation.
(using -O3 for all compilations)
GCC 3.4 has an 84-byte stack frame, and a body of 372 instructions.
GCC 4.1 has a 1416-byte stack frame, and a body of 1668 instructions.
GCC 4.2 has a 1320-byte stack frame, and a body of 1565 instructions.
--
Summary: 4.1, 4.2 (possibly 4.0?) not using mulsidi3
Product: gcc
Version: 4.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: eplondke at gmail dot com
GCC host triplet: x86_64-suse-linux
GCC target triplet: arm-unkown-elf
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29274