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[LCSSA] Handle PHI insertion in disjoint loops

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Take two disjoint Loops L1 and L2.

LoopSimplify fails to simplify some loops (e.g. when indirect branches
are involved). In such situations, it can happen that an exit for L1 is
the header of L2. Thus, when we create PHIs in one of such exits we are
also inserting PHIs in L2 header.

This could break LCSSA form for L2 because these inserted PHIs can also
have uses in L2 exits, which are never handled in the current
implementation. Provide a fix for this corner case and test that we
don't assert/crash on that.

Differential Revision: http://reviews.llvm.org/D6624

rdar://problem/19166231

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224740 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bruno Cardoso Lopes
2014-12-22 22:35:46 +00:00
parent e5ca21a2df
commit a559a2317c
5 changed files with 83 additions and 16 deletions
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5
include/llvm/Transforms/Utils/LoopUtils.h
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@ -49,7 +49,8 @@ bool simplifyLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, Pass *PP,
/// If ScalarEvolution is passed in, it will be preserved.
///
/// Returns true if any modifications are made to the loop.
bool formLCSSA(Loop &L, DominatorTree &DT, ScalarEvolution *SE = nullptr);
bool formLCSSA(Loop &L, DominatorTree &DT, LoopInfo *LI,
ScalarEvolution *SE = nullptr);
/// \brief Put a loop nest into LCSSA form.
///
@ -60,7 +61,7 @@ bool formLCSSA(Loop &L, DominatorTree &DT, ScalarEvolution *SE = nullptr);
/// If ScalarEvolution is passed in, it will be preserved.
///
/// Returns true if any modifications are made to the loop.
bool formLCSSARecursively(Loop &L, DominatorTree &DT,
bool formLCSSARecursively(Loop &L, DominatorTree &DT, LoopInfo *LI,
ScalarEvolution *SE = nullptr);
}