Evan Cheng 733c6b1db1 LLVM sdisel normalize bit extraction of the form: ... ((x & 0xff00) >> 8) << 2 to (x >> 6) & 0x3fc This is general goodness since it folds a left shift into the mask. However, the trailing zeros in the mask prevents the ARM backend from using the bit extraction instructions. And worse since the mask materialization may require an addition instruction. This comes up fairly frequently when the result of the bit twiddling is used as memory address. e.g. = ptr[(x & 0xFF0000) >> 16] We want to generate: ubfx r3, r1, #16, #8 ldr.w r3, [r0, r3, lsl #2] vs. mov.w r9, #1020 and.w r2, r9, r1, lsr #14 ldr r2, [r0, r2] Add a late ARM specific isel optimization to ARMDAGToDAGISel::PreprocessISelDAG(). It folds the left shift to the 'base + offset' address computation; change the mask to one which doesn't have trailing zeros and enable the use of ubfx. Note the optimization has to be done late since it's target specific and we don't want to change the DAG normalization. It's also fairly restrictive as shifter operands are not always free. It's only done for lsh 1 / 2. It's known to be free on some cpus and they are most common for address computation. This is a slight win for blowfish, rijndael, etc. rdar://12870177 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170581 91177308-0d34-0410-b5e6-96231b3b80d8		2012-12-19 20:16:09 +00:00
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Analysis	Reverse order of checking SSE level when calculating compare cost, so we check	2012-12-18 22:57:56 +00:00
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CodeGen	LLVM sdisel normalize bit extraction of the form:	2012-12-19 20:16:09 +00:00
DebugInfo	Add support for passing -main-file-name all the way through to	2012-12-18 00:31:01 +00:00
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Instrumentation	[msan] Heuristically instrument unknown intrinsics.	2012-12-19 11:22:04 +00:00
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MC	Remove edis - the enhanced disassembler. Fixes PR14654.	2012-12-19 19:55:47 +00:00
Object	Teach MachO which sections contain code	2012-12-17 17:59:32 +00:00
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TableGen	Fix typo, which prevent test from being check.	2012-12-12 21:10:56 +00:00
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Transforms	Transform (x&C)>V into (x&C)!=0 where possible	2012-12-19 19:47:13 +00:00
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YAMLParser	Convert the uses of '|&' to use '2>&1 |' instead, which works on old	2012-07-02 18:37:59 +00:00
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