Move isGuaranteedToExecute out of LICM.
Also rename LICMSafetyInfo to LoopSafetyInfo.
Both will be used in LoopUnswitch in a separate change.
llvm-svn: 272420
diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 4cc227d..3009313 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -925,3 +925,42 @@
}
return None;
}
+
+/// Returns true if the instruction in a loop is guaranteed to execute at least
+/// once.
+bool llvm::isGuaranteedToExecute(const Instruction &Inst,
+ const DominatorTree *DT, const Loop *CurLoop,
+ const LoopSafetyInfo *SafetyInfo) {
+ // We have to check to make sure that the instruction dominates all
+ // of the exit blocks. If it doesn't, then there is a path out of the loop
+ // which does not execute this instruction, so we can't hoist it.
+
+ // If the instruction is in the header block for the loop (which is very
+ // common), it is always guaranteed to dominate the exit blocks. Since this
+ // is a common case, and can save some work, check it now.
+ if (Inst.getParent() == CurLoop->getHeader())
+ // If there's a throw in the header block, we can't guarantee we'll reach
+ // Inst.
+ return !SafetyInfo->HeaderMayThrow;
+
+ // Somewhere in this loop there is an instruction which may throw and make us
+ // exit the loop.
+ if (SafetyInfo->MayThrow)
+ return false;
+
+ // Get the exit blocks for the current loop.
+ SmallVector<BasicBlock *, 8> ExitBlocks;
+ CurLoop->getExitBlocks(ExitBlocks);
+
+ // Verify that the block dominates each of the exit blocks of the loop.
+ for (BasicBlock *ExitBlock : ExitBlocks)
+ if (!DT->dominates(Inst.getParent(), ExitBlock))
+ return false;
+
+ // As a degenerate case, if the loop is statically infinite then we haven't
+ // proven anything since there are no exit blocks.
+ if (ExitBlocks.empty())
+ return false;
+
+ return true;
+}