SCEVExpander::expandAddRecExprLiterally(): check before casting as Instruction
Summary:
An alternative to D48597.
Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=37936 | PR37936 ]].
The problem is as follows:
1. `indvars` marks `%dec` as `NUW`.
2. `loop-instsimplify` runs `instsimplify`, which constant-folds `%dec` to -1 (D47908)
3. `loop-reduce` tries to do some further modification, but crashes
with an type assertion in cast, because `%dec` is no longer an `Instruction`,
If the runline is split into two, i.e. you first run `-indvars -loop-instsimplify`,
store that into a file, and then run `-loop-reduce`, there is no crash.
So it looks like the problem is due to `-loop-instsimplify` not discarding SCEV.
But in this case we can just not crash if it's not an `Instruction`.
This is just a local fix, unlike D48597, so there may very well be other problems.
Reviewers: mkazantsev, uabelho, sanjoy, silviu.baranga, wmi
Reviewed By: mkazantsev
Subscribers: evstupac, javed.absar, spatel, llvm-commits
Differential Revision: https://reviews.llvm.org/D48599
llvm-svn: 335950
diff --git a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
index f2ce0f4..7f76f05 100644
--- a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -1169,8 +1169,11 @@
if (!IsMatchingSCEV && !TryNonMatchingSCEV)
continue;
+ // TODO: this possibly can be reworked to avoid this cast at all.
Instruction *TempIncV =
- cast<Instruction>(PN.getIncomingValueForBlock(LatchBlock));
+ dyn_cast<Instruction>(PN.getIncomingValueForBlock(LatchBlock));
+ if (!TempIncV)
+ continue;
// Check whether we can reuse this PHI node.
if (LSRMode) {