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Benjamin Kramer eba5ed591b Cache the hash value of the operands in the MDNode.
FoldingSet is implemented as a chained hash table. When there is a hash
collision during insertion, which is common as we fill the table until a
load factor of 2.0 is hit, we walk the chained elements, comparing every
operand with the new element's operands. This can be very expensive if the
MDNode has many operands.

We sacrifice a word of space in MDNode to cache the full hash value, reducing
compares on collision to a minimum. MDNode grows from 28 to 32 bytes + operands
on x86. On x86_64 the new bits fit nicely into existing padding, not growing
the struct at all.

The actual speedup depends a lot on the test case and is typically between
1% and 2% for C++ code with clang -c -O0 -g.

llvm-svn: 154497
2012-04-11 14:06:54 +00:00
autoconf Fix a problem in the target detection for Debian GNU/HURD 2012-04-05 19:34:15 +00:00
bindings [python] Add negative MemoryBuffer testcase 2012-03-22 11:23:52 +00:00
cmake Add InitializeNativeTargetDisassembler function. 2012-03-26 21:56:56 +00:00
docs Express the number of ULPs in fpaccuracy metadata as a real rather than a 2012-04-10 08:22:43 +00:00
examples Switch to a more idiomatic way of silencing unused variable warnings in 2012-02-20 00:02:49 +00:00
include Cache the hash value of the operands in the MDNode. 2012-04-11 14:06:54 +00:00
lib Cache the hash value of the operands in the MDNode. 2012-04-11 14:06:54 +00:00
projects Fix a problem in the target detection for Debian GNU/HURD 2012-04-05 19:34:15 +00:00
runtime Use the correct filename for the error message. 2012-03-28 02:39:06 +00:00
test Add more fused mul+add/sub patterns. rdar://10139676 2012-04-11 06:59:47 +00:00
tools llvm-stress: stop abusing ConstantFP::get() 2012-04-10 22:44:51 +00:00
unittests Add YAML parser to Support. 2012-04-03 23:09:22 +00:00
utils Tablegen'd regpressure: emit the weighted pressure limit. 2012-04-11 04:31:33 +00:00
.gitignore git: Add tools/lldb to the ignore list. 2011-11-10 22:55:50 +00:00
CMakeLists.txt Add YAML parser to Support. 2012-04-03 23:09:22 +00:00
configure Fix a problem in the target detection for Debian GNU/HURD 2012-04-05 19:34:15 +00:00
CREDITS.TXT sort by alpha. 2012-03-12 21:12:59 +00:00
LICENSE.TXT Add YAML parser to Support. 2012-04-03 23:09:22 +00:00
llvm.spec.in Tidy up. s/Low Level Virtual Machine/LLVM/. 2012-01-25 22:00:23 +00:00
LLVMBuild.txt LLVMBuild: Introduce a common section which currently has a list of the 2011-12-12 22:45:54 +00:00
Makefile Makefile: add missing files to FilesToConfig 2012-01-17 02:56:49 +00:00
Makefile.common Removed trailing whitespace from Makefiles. 2009-01-09 16:44:42 +00:00
Makefile.config.in Add profiling support for Intel Parallel Amplifier XE (VTune) for JITted code in LLVM. 2012-03-13 08:33:15 +00:00
Makefile.rules Use a posix compliant regexp in export file construction. 2012-03-12 20:58:14 +00:00
README.txt test commit 2012-03-20 13:12:38 +00:00

Low Level Virtual Machine (LLVM)
================================

This directory and its subdirectories contain source code for the Low Level
Virtual Machine, a toolkit for the construction of highly optimized compilers,
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Please see the HTML documentation provided in docs/index.html for further
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