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c5d63dfc6a
This patch introduces guard based loop predication optimization. The new LoopPredication pass tries to convert loop variant range checks to loop invariant by widening checks across loop iterations. For example, it will convert
for (i = 0; i < n; i++) {
guard(i < len);
...
}
to
for (i = 0; i < n; i++) {
guard(n - 1 < len);
...
}
After this transformation the condition of the guard is loop invariant, so loop-unswitch can later unswitch the loop by this condition which basically predicates the loop by the widened condition:
if (n - 1 < len)
for (i = 0; i < n; i++) {
...
}
else
deoptimize
This patch relies on an NFC change to make ScalarEvolution::isMonotonicPredicate public (revision 293062).
Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D29034
llvm-svn: 293064
33 lines
1.1 KiB
C++
33 lines
1.1 KiB
C++
//===- LoopPredication.h - Guard based loop predication pass ----*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass tries to convert loop variant range checks to loop invariant by
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// widening checks across loop iterations.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_SCALAR_LOOPPREDICATION_H
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#define LLVM_TRANSFORMS_SCALAR_LOOPPREDICATION_H
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/Transforms/Scalar/LoopPassManager.h"
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namespace llvm {
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/// Performs Loop Predication Pass.
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class LoopPredicationPass : public PassInfoMixin<LoopPredicationPass> {
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public:
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PreservedAnalyses run(Loop &L, LoopAnalysisManager &AM,
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LoopStandardAnalysisResults &AR, LPMUpdater &U);
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};
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} // end namespace llvm
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#endif // LLVM_TRANSFORMS_SCALAR_LOOPPREDICATION_H
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