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From: "mans at mansr dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/54974] New: [ARM] Incorrect placement of constant pools Date: Thu, 18 Oct 2012 12:58:00 -0000 [thread overview] Message-ID: <bug-54974-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54974 Bug #: 54974 Summary: [ARM] Incorrect placement of constant pools Classification: Unclassified Product: gcc Version: 4.8.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target AssignedTo: unassigned@gcc.gnu.org ReportedBy: mans@mansr.com Created attachment 28483 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28483 Test case If the following conditions are true, a constant pool is placed too far from an LDR instruction accessing it: - Compiling to Thumb2. - There is no unconditional branch within 4k of the LDR instruction. - At least one of: * The LDR instruction is not at a 4-byte aligned address. * There is an instruction boundary 4094 bytes from the value of PC at the LDR. The problem here is twofold: 1. The base address of a PC-relative LDR in Thumb2 is the address of the instruction plus 4, rounded down to a multiple of 4. The calculation for the valid range fails to take this rounding into account. 2. The constant pool is (rightly) 4-byte aligned. When scanning the instructions for a suitable location, the possible need for padding is not considered. The problem can be seen by compiling the attached preprocessed source using flags "-mthumb -march=armv7-a -mfpu=vfpv3-d16 -mfloat-abi=hard -O0 -fPIC".
next reply other threads:[~2012-10-18 12:58 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-10-18 12:58 mans at mansr dot com [this message] 2012-10-18 13:01 ` [Bug target/54974] " mans at mansr dot com 2012-10-18 13:20 ` [Bug target/54974] [4.8 Regression] " doko at gcc dot gnu.org 2012-10-18 13:23 ` mikpe at it dot uu.se 2012-10-18 18:09 ` pinskia at gcc dot gnu.org 2012-10-18 19:43 ` mikpe at it dot uu.se 2012-10-19 12:24 ` doko at gcc dot gnu.org 2012-11-28 3:04 ` [Bug target/54974] [4.7/4.8 Regression] [ARM] [thumb] " ramana at gcc dot gnu.org 2012-11-29 10:02 ` mgretton at gcc dot gnu.org 2012-12-03 15:58 ` [Bug target/54974] [4.7 " rguenth at gcc dot gnu.org 2012-12-11 17:36 ` ramana at gcc dot gnu.org 2013-04-11 7:59 ` rguenth at gcc dot gnu.org 2014-06-12 13:19 ` rguenth at gcc dot gnu.org
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