Jakob Stoklund Olesen 0d5fcae6cd Defer some shl transforms to DAGCombine. ... The shl instruction is used to represent multiplication by a constant power of two as well as bitwise left shifts. Some InstCombine transformations would turn an shl instruction into a bit mask operation, making it difficult for later analysis passes to recognize the constsnt multiplication. Disable those shl transformations, deferring them to DAGCombine time. An 'shl X, C' instruction is now treated mostly the same was as 'mul X, C'. These transformations are deferred: (X >>? C) << C --> X & (-1 << C) (When X >> C has multiple uses) (X >>? C1) << C2 --> X << (C2-C1) & (-1 << C2) (When C2 > C1) (X >>? C1) << C2 --> X >>? (C1-C2) & (-1 << C2) (When C1 > C2) The corresponding exact transformations are preserved, just like div-exact + mul: (X >>?,exact C) << C --> X (X >>?,exact C1) << C2 --> X << (C2-C1) (X >>?,exact C1) << C2 --> X >>?,exact (C1-C2) The disabled transformations could also prevent the instruction selector from recognizing rotate patterns in hash functions and cryptographic primitives. I have a test case for that, but it is too fragile. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155136 91177308-0d34-0410-b5e6-96231b3b80d8		2012-04-19 16:46:26 +00:00
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Hello
InstCombine	Defer some shl transforms to DAGCombine.	2012-04-19 16:46:26 +00:00
Instrumentation	[tsan] two more compile-time optimizations:	2012-04-10 22:29:17 +00:00
IPO	Add a Fixme.	2012-04-16 04:23:52 +00:00
Scalar	Don't crash on code where the user put __attribute__((constructor)) on	2012-04-18 22:24:33 +00:00
Utils	Fix 12513: Loop unrolling breaks with indirect branches.	2012-04-10 05:14:42 +00:00
Vectorize	Fix style violation in BBVectorize (pointed out by Bill Wendling)	2012-04-16 12:39:17 +00:00
CMakeLists.txt	Add a basic-block autovectorization pass.	2012-02-01 03:51:43 +00:00
LLVMBuild.txt	Add a basic-block autovectorization pass.	2012-02-01 03:51:43 +00:00
Makefile	Add a basic-block autovectorization pass.	2012-02-01 03:51:43 +00:00