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Hal Finkel 3da41a28a1 Revert "Revert '[DAGCombiner] Split up an indexed load if only the base pointer value is live'"
I reverted r208640 in r209747 because r208640 broke self-hosting on PPC64. The
underlying cause of the failure is that pre-inc loads with increments
represented by ISD::TargetConstants were being transformed into ISD:::ADDs with
ISD::TargetConstant operands. PPC doesn't have a pattern for those, and so they
were selected as invalid r+r adds.

This recommits r208640, rebased and with an exclusion for ISD::TargetConstant
increments. This behavior seems correct, although in the future we might want
to ask the target to split out the indexing that uses ISD::TargetConstants.

Unfortunately, I don't yet have small test case where the relevant invalid
'add' instruction is not itself dead (and thus eliminated by
DeadMachineInstructionElim -- sometimes bugpoint is too good at removing things)

Original commit message (by Adam Nemet):

Right now the load may not get DCE'd because of the side-effect of updating
the base pointer.

This can happen if we lower a read-modify-write of an illegal larger type
(e.g. i48) such that the modification only affects one of the subparts (the
lower i32 part but not the higher i16 part).  See the testcase.

In order to spot the dead load we need to revisit it when SimplifyDemandedBits
decided that the value of the load is masked off.  This is the
CommitTargetLoweringOpt piece.

I checked compile time with ARM64 by sending SPEC bitcode files through llc.
No measurable change.

Fixes <rdar://problem/16031651>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216898 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-02 06:24:04 +00:00
autoconf Delete support for AuroraUX. 2014-08-14 15:15:09 +00:00
bindings [OCaml] Expose Llvm.get_operand_use. 2014-08-12 02:55:45 +00:00
cmake Introduce -DLLVM_USE_SANITIZER=Undefined CMake option to build UBSan-ified version of LLVM/Clang. 2014-08-29 00:50:36 +00:00
docs Fix typos in comments, NFC 2014-08-29 21:53:01 +00:00
examples Modernize raw_fd_ostream's constructor a bit. 2014-08-25 18:16:47 +00:00
include MC: remove unnecessary enumeration prefix 2014-09-01 23:48:29 +00:00
lib Revert "Revert '[DAGCombiner] Split up an indexed load if only the base pointer value is live'" 2014-09-02 06:24:04 +00:00
projects [cmake] Use the external project machinery for libcxxabi so that it can 2014-07-25 10:27:40 +00:00
test Revert "Revert '[DAGCombiner] Split up an indexed load if only the base pointer value is live'" 2014-09-02 06:24:04 +00:00
tools Teach llvm-bcanalyzer to use one stream's BLOCKINFO to read another stream. 2014-08-30 17:07:55 +00:00
unittests Add some negative (and positive) static_assert checks for ArrayRef-of-pointer conversions introduced in r216709 2014-08-31 01:33:41 +00:00
utils Fix typos in comments, NFC 2014-08-29 21:53:01 +00:00
.arcconfig Updated phabricator server. 2014-04-07 03:57:04 +00:00
.clang-format
.gitignore Add Polly to the ignored trees. 2014-06-25 13:13:36 +00:00
CMakeLists.txt Fix building with in-tree libc++abi on FreeBSD 2014-08-01 19:23:15 +00:00
CODE_OWNERS.TXT Add a sentence that all entries should include an email address. 2014-08-04 19:33:25 +00:00
configure Delete support for AuroraUX. 2014-08-14 15:15:09 +00:00
CREDITS.TXT Rise from the dead and update personal info 2014-08-25 17:51:04 +00:00
LICENSE.TXT Remove projects/sample. 2014-03-12 22:40:22 +00:00
llvm.spec.in
LLVMBuild.txt
Makefile [configure/make] Propagate names of build host tools when making BuildTools 2014-03-25 21:45:41 +00:00
Makefile.common
Makefile.config.in Track clang r213171 2014-07-16 16:50:34 +00:00
Makefile.rules Delete support for AuroraUX. 2014-08-14 15:15:09 +00:00
README.txt Trivial test commit. 2014-04-26 19:05:45 +00:00

Low Level Virtual Machine (LLVM)
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