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From: "irar at il dot ibm dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/33447] New: Non-empty latch block prevents loop vectorization
Date: Sun, 16 Sep 2007 11:49:00 -0000 [thread overview]
Message-ID: <bug-33447-9531@http.gcc.gnu.org/bugzilla/> (raw)
The following loop (from linpk.f90) contains a non-empty latch block before
tree optimizations:
Source code:
Line
m = MOD(N,4)
323 IF ( m.NE.0 ) THEN
324 DO i = 1 , m
325 Dy(i) = Dy(i) + Da*Dx(i)
326 ENDDO
327 IF ( N.LT.4 ) RETURN
328 ENDIF
329 mp1 = m + 1
330 DO i = mp1 , N , 4
331 Dy(i) = Dy(i) + Da*Dx(i)
332 Dy(i+1) = Dy(i+1) + Da*Dx(i+1)
333 Dy(i+2) = Dy(i+2) + Da*Dx(i+2)
334 Dy(i+3) = Dy(i+3) + Da*Dx(i+3)
335 ENDDO
The first SSA dump:
<bb 17>:
...
if (countm1.32_8 == 0)
goto <bb 19>;
else
goto <bb 18>;
<bb 18>:
countm1.32_98 = countm1.32_8 + 4294967295;
goto <bb 17>;
This is also related to PR 28643 and PR 33244. However, in these PRs some tree
optimization puts stmts/phi nodes in the latch block, while in the lnpck
example the latch block is non-empty to begin with.
--
Summary: Non-empty latch block prevents loop vectorization
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: irar at il dot ibm dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33447
next reply other threads:[~2007-09-16 11:49 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-16 11:49 irar at il dot ibm dot com [this message]
2009-01-03 0:52 ` [Bug tree-optimization/33447] " steven at gcc dot gnu dot org
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