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Instead of producing code like this: Loop: X = phi 0, X2 ... X2 = X + 1 if (X != N-1) goto Loop We now generate code that looks like this: Loop: X = phi 0, X2 ... X2 = X + 1 if (X2 != N) goto Loop This has two big advantages: 1. The trip count of the loop is now explicit in the code, allowing the direct implementation of Loop::getTripCount() 2. This reduces register pressure in the loop, and allows X and X2 to be put into the same register. As a consequence of the second point, the code we generate for loops went from: .LBB2: # no_exit.1 ... mov %EDI, %ESI inc %EDI cmp %ESI, 2 mov %ESI, %EDI jne .LBB2 # PC rel: no_exit.1 To: .LBB2: # no_exit.1 ... inc %ESI cmp %ESI, 3 jne .LBB2 # PC rel: no_exit.1 ... which has two fewer moves, and uses one less register. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12961 91177308-0d34-0410-b5e6-96231b3b80d8 |
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.. | ||
Hello | ||
Instrumentation | ||
IPO | ||
Scalar | ||
Utils | ||
ExprTypeConvert.cpp | ||
LevelRaise.cpp | ||
Makefile | ||
TransformInternals.cpp | ||
TransformInternals.h |