Juergen Ributzka fb282c68b7 Add Constant Hoisting Pass ... This pass identifies expensive constants to hoist and coalesces them to better prepare it for SelectionDAG-based code generation. This works around the limitations of the basic-block-at-a-time approach. First it scans all instructions for integer constants and calculates its cost. If the constant can be folded into the instruction (the cost is TCC_Free) or the cost is just a simple operation (TCC_BASIC), then we don't consider it expensive and leave it alone. This is the default behavior and the default implementation of getIntImmCost will always return TCC_Free. If the cost is more than TCC_BASIC, then the integer constant can't be folded into the instruction and it might be beneficial to hoist the constant. Similar constants are coalesced to reduce register pressure and materialization code. When a constant is hoisted, it is also hidden behind a bitcast to force it to be live-out of the basic block. Otherwise the constant would be just duplicated and each basic block would have its own copy in the SelectionDAG. The SelectionDAG recognizes such constants as opaque and doesn't perform certain transformations on them, which would create a new expensive constant. This optimization is only applied to integer constants in instructions and simple (this means not nested) constant cast experessions. For example: %0 = load i64* inttoptr (i64 big_constant to i64*) Reviewed by Eric git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200022 91177308-0d34-0410-b5e6-96231b3b80d8		2014-01-24 18:23:08 +00:00
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Analysis	Add Constant Hoisting Pass	2014-01-24 18:23:08 +00:00
AsmParser
Bitcode
CodeGen	Add Constant Hoisting Pass	2014-01-24 18:23:08 +00:00
DebugInfo	DWARFContext: Fix possible memory leak since r198908.	2014-01-24 13:40:43 +00:00
ExecutionEngine	Fix known typos	2014-01-24 17:20:08 +00:00
IR
IRReader
Linker
LTO	Most streamers' InitSections just create a text section. Make that the default	2014-01-24 02:42:26 +00:00
MC	Fix known typos	2014-01-24 17:20:08 +00:00
Object
Option
Support	Fix known typos	2014-01-24 17:20:08 +00:00
TableGen
Target	Add Constant Hoisting Pass	2014-01-24 18:23:08 +00:00
Transforms	Add Constant Hoisting Pass	2014-01-24 18:23:08 +00:00
CMakeLists.txt
LLVMBuild.txt
Makefile