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Reword and tidy up some comments.
llvm-svn: 70416
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@ -10,33 +10,44 @@
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// This file implements Loop Index Splitting Pass. This pass handles three
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// kinds of loops.
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//
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// [1] Loop is eliminated when loop body is executed only once. For example,
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// [1] A loop may be eliminated if the body is executed exactly once.
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// For example,
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//
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// for (i = 0; i < N; ++i) {
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// if (i == X) {
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// ...
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// body;
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// }
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// }
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//
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// [2] Loop's iteration space is shrunk if loop body is executed for certain
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// range only. For example,
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// is transformed to
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//
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// i = X;
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// body;
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//
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// [2] A loop's iteration space may be shrunk if the loop body is executed
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// for a proper sub-range of the loop's iteration space. For example,
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//
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// for (i = 0; i < N; ++i) {
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// if (i > A && i < B) {
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// ...
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// }
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// }
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// is trnasformed to iterators from A to B, if A > 0 and B < N.
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//
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// [3] Loop is split if the loop body is dominated by an branch. For example,
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// is transformed to iterators from A to B, if A > 0 and B < N.
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//
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// [3] A loop may be split if the loop body is dominated by a branch.
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// For example,
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//
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// for (i = LB; i < UB; ++i) { if (i < SV) A; else B; }
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//
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// is transformed into
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//
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// AEV = BSV = SV
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// for (i = LB; i < min(UB, AEV); ++i)
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// A;
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// for (i = max(LB, BSV); i < UB; ++i);
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// B;
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "loop-index-split"
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