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IVUsers should only generate SCEV's for values that are safe to speculate.

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This allows SCEVExpander to run on the IV expressions.

This codifies an assumption made by LSR to complete the fix for
PR11356, but I haven't been able to generate a separate unit test for
this part. I'm adding it as an extra safety check.

llvm-svn: 160204
This commit is contained in:
Andrew Trick 2012-07-13 23:33:05 +00:00
parent 7efd13174a
commit 2582249334
1 changed files with 7 additions and 0 deletions
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7
lib/Analysis/IVUsers.cpp
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@ -21,6 +21,7 @@
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/ADT/STLExtras.h"
@ -120,6 +121,12 @@ bool IVUsers::AddUsersImpl(Instruction *I,
if (!SE->isSCEVable(I->getType()))
return false; // Void and FP expressions cannot be reduced.
// IVUsers is used by LSR which assumes that all SCEV expressions are safe to
// pass to SCEVExpander. Expressions are not safe to expand if they represent
// operations that are not safe to speculate, namely integer division.
if (!isa<PHINode>(I) && !isSafeToSpeculativelyExecute(I, TD))
return false;
// LSR is not APInt clean, do not touch integers bigger than 64-bits.
// Also avoid creating IVs of non-native types. For example, we don't want a
// 64-bit IV in 32-bit code just because the loop has one 64-bit cast.