Move FindAvailableLoadedValue isSafeToLoadUnconditionally out of

lib/Transforms/Utils and into lib/Analysis so that Analysis passes
can use them.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@104949 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 51 insertions, 0 deletions

diff --git a/include/llvm/Analysis/Loads.h b/include/llvm/Analysis/Loads.h
new file mode 100644
index 0000000000..1574262dd6
--- /dev/null
+++ b/include/llvm/Analysis/Loads.h
@@ -0,0 +1,51 @@
+//===- Loads.h - Local load analysis --------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares simple local analyses for load instructions.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_LOADS_H
+#define LLVM_ANALYSIS_LOADS_H
+
+#include "llvm/BasicBlock.h"
+
+namespace llvm {
+
+class AliasAnalysis;
+class TargetData;
+
+/// isSafeToLoadUnconditionally - Return true if we know that executing a load
+/// from this value cannot trap.  If it is not obviously safe to load from the
+/// specified pointer, we do a quick local scan of the basic block containing
+/// ScanFrom, to determine if the address is already accessed.
+bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
+                                 unsigned Align, const TargetData *TD = 0);
+
+/// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at
+/// the instruction before ScanFrom) checking to see if we have the value at
+/// the memory address *Ptr locally available within a small number of
+///  instructions. If the value is available, return it.
+///
+/// If not, return the iterator for the last validated instruction that the 
+/// value would be live through.  If we scanned the entire block and didn't
+/// find something that invalidates *Ptr or provides it, ScanFrom would be
+/// left at begin() and this returns null.  ScanFrom could also be left 
+///
+/// MaxInstsToScan specifies the maximum instructions to scan in the block.
+/// If it is set to 0, it will scan the whole block. You can also optionally
+/// specify an alias analysis implementation, which makes this more precise.
+Value *FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
+                                BasicBlock::iterator &ScanFrom,
+                                unsigned MaxInstsToScan = 6,
+                                AliasAnalysis *AA = 0);
+
+}
+
+#endif