llvm-project/llvm
Arnold Schwaighofer a92eeebde8 LoopVectorizer: Disallow reductions whose header phi is used outside the loop
If an outside loop user of the reduction value uses the header phi node we
cannot just reduce the vectorized phi value in the vector code epilog because
we would loose VF-1 reductions.

lp:
  p = phi (0, lv)
  lv = lv + 1
  ...
  brcond , lp, outside

outside:
  usr = add 0, p

(Say the loop iterates two times, the value of p coming out of the loop is one).

We cannot just transform this to:

vlp:
  p = phi (<0,0>, lv)
  lv = lv + <1,1>
  ..
  brcond , lp, outside

outside:
  p_reduced = p[0] + [1];
  usr = add 0, p_reduced

(Because the original loop iterated two times the vectorized loop would iterate
one time, but p_reduced ends up being zero instead of one).

We would have to execute VF-1 iterations in the scalar remainder loop in such
cases. For now, just disable vectorization.

PR16522

llvm-svn: 186256
2013-07-13 19:09:29 +00:00
..
autoconf No ',' between programs. 2013-07-08 21:18:54 +00:00
bindings We're in 3.4 land now. 2013-05-07 20:31:28 +00:00
cmake Find xdot or xdot.py. 2013-07-08 20:24:54 +00:00
docs R600: Add ISA documents to the CompilerWriterInfo page 2013-07-12 18:14:40 +00:00
examples ExceptionDemo: Corresponding to r181820, SectionMemoryManager should belong to RTDyldMemoryManager. 2013-05-14 23:05:00 +00:00
include Remove unneeded forward declarations. 2013-07-13 08:28:45 +00:00
lib LoopVectorizer: Disallow reductions whose header phi is used outside the loop 2013-07-13 19:09:29 +00:00
projects The build system is currently miss-identifying GNU/kFreeBSD as FreeBSD. 2013-07-01 08:07:52 +00:00
runtime Remove "-Wl,-seg1addr -Wl,0xE0000000" from link options. 2013-06-04 15:26:37 +00:00
test LoopVectorizer: Disallow reductions whose header phi is used outside the loop 2013-07-13 19:09:29 +00:00
tools Try to open the file before use data from stat. 2013-07-13 05:07:22 +00:00
unittests Attempt at fixing a mingw bot. 2013-07-13 12:36:30 +00:00
utils Add new directive called CHECK-LABEL to FileCheck. 2013-07-12 14:51:05 +00:00
.arcconfig
.gitignore
CMakeLists.txt Support using "host" as a target in LLVM_TARGETS_TO_BUILD when using cmake. 2013-06-26 07:57:53 +00:00
CODE_OWNERS.TXT Add more owners to CODE_OWNERS.TXT (Kostya Serebryany: AddressSanitizer and ThreadSanitizer; Evgeniy Stepanov: MemorySanitizer) 2013-06-27 08:47:12 +00:00
CREDITS.TXT Identify me on IRC. 2013-06-18 22:09:36 +00:00
LICENSE.TXT Be more specific and capitalize filenames. 2013-05-21 21:22:34 +00:00
LLVMBuild.txt
Makefile Fix regular expression used by 'make update' to only look for 'I' and '?' at the start of svn info results and to check for spaces after 'I' instead of just after '?'. 2013-07-03 14:48:37 +00:00
Makefile.common
Makefile.config.in Add an autoconf option for turning on -gsplit-dwarf by default 2013-06-25 01:12:25 +00:00
Makefile.rules The build system is currently miss-identifying GNU/kFreeBSD as FreeBSD. 2013-07-01 08:07:52 +00:00
README.txt test 2013-04-17 05:34:03 +00:00
configure No ',' between programs. 2013-07-08 21:18:54 +00:00
llvm.spec.in

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