Benjamin Kramer 611afc0620 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. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154497 91177308-0d34-0410-b5e6-96231b3b80d8		2012-04-11 14:06:54 +00:00
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llvm	Cache the hash value of the operands in the MDNode.	2012-04-11 14:06:54 +00:00
llvm-c	Add a C binding to the Target and TargetMachine classes to allow for emitting	2012-04-11 10:25:24 +00:00