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Chris Lattner
895c4ab564
Fold (x << c1)>> c2 into a single shift if the bits shifted out aren't used.
This compiles: int baz(long long a) { return (short)(((int)(a >>24)) >> 9); } into: _baz: srwi r2, r3, 1 extsh r3, r2 blr on PPC, instead of: _baz: slwi r2, r3, 8 srwi r2, r2, 9 extsh r3, r2 blr GCC produces: _baz: srwi r10,r4,24 insrwi r10,r3,24,0 srawi r9,r3,24 srawi r3,r10,9 extsh r3,r3 blr This implements CodeGen/PowerPC/shl_elim.ll git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36221 91177308-0d34-0410-b5e6-96231b3b80d8
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