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Introduce a new LoopInfo utility function makeLoopInvariant, which

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works similar to isLoopInvariant, except that it will do trivial
hoisting to try to make the value loop invariant if it isn't already.
This makes it easier for transformation passes to clear trivial
instructions out of the way (the regular LICM pass doesn't run
until relatively late). This is code factored out of LoopSimplify
and other places.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75578 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-07-14 01:06:29 +00:00
parent b9e126ce7d
commit a342026504
2 changed files with 89 additions and 1 deletions
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include/llvm/Analysis/LoopInfo.h
+27
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@@ -476,6 +476,33 @@ public:
///
bool isLoopInvariant(Value *V) const;
/// isLoopInvariant - Return true if the specified instruction is
/// loop-invariant.
///
bool isLoopInvariant(Instruction *I) const;
/// makeLoopInvariant - If the given value is an instruciton inside of the
/// loop and it can be hoisted, do so to make it trivially loop-invariant.
/// Return true if the value after any hoisting is loop invariant. This
/// function can be used as a slightly more aggressive replacement for
/// isLoopInvariant.
///
/// If InsertPt is specified, it is the point to hoist instructions to.
/// If null, the terminator of the loop preheader is used.
///
bool makeLoopInvariant(Value *V, Instruction *InsertPt = 0) const;
/// makeLoopInvariant - If the given instruction is inside of the
/// loop and it can be hoisted, do so to make it trivially loop-invariant.
/// Return true if the instruction after any hoisting is loop invariant. This
/// function can be used as a slightly more aggressive replacement for
/// isLoopInvariant.
///
/// If InsertPt is specified, it is the point to hoist instructions to.
/// If null, the terminator of the loop preheader is used.
///
bool makeLoopInvariant(Instruction *I, Instruction *InsertPt = 0) const;
/// getCanonicalInductionVariable - Check to see if the loop has a canonical
/// induction variable: an integer recurrence that starts at 0 and increments
/// by one each time through the loop. If so, return the phi node that