[llvm-commits] [llvm] r60166 - in /llvm/trunk: include/llvm/Transforms/Utils/BasicBlockUtils.h lib/Transforms/Scalar/JumpThreading.cpp lib/Transforms/Utils/BasicBlockUtils.cpp
Chris Lattner
sabre at nondot.org
Thu Nov 27 00:10:08 PST 2008
Author: lattner
Date: Thu Nov 27 02:10:05 2008
New Revision: 60166
URL: http://llvm.org/viewvc/llvm-project?rev=60166&view=rev
Log:
move FindAvailableLoadedValue from JumpThreading to Transforms/Utils.
Modified:
llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h
llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp
Modified: llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h?rev=60166&r1=60165&r2=60166&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h Thu Nov 27 02:10:05 2008
@@ -24,6 +24,7 @@
class Instruction;
class Pass;
+class AliasAnalysis;
/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
/// if possible. The return value indicates success or failure.
@@ -47,6 +48,25 @@
//
void ReplaceInstWithInst(Instruction *From, Instruction *To);
+/// 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);
+
+
// RemoveSuccessor - Change the specified terminator instruction such that its
// successor #SuccNum no longer exists. Because this reduces the outgoing
Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=60166&r1=60165&r2=60166&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Thu Nov 27 02:10:05 2008
@@ -243,67 +243,6 @@
return false;
}
-
-/// FindAvailableLoadedValue - Scan backwards from 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, ScanFrom would
-/// be left at begin().
-///
-/// FIXME: Move this to transform utils and use from
-/// InstCombiner::visitLoadInst. It would also be nice to optionally take AA so
-/// that GVN could do this.
-static Value *FindAvailableLoadedValue(Value *Ptr,
- BasicBlock *ScanBB,
- BasicBlock::iterator &ScanFrom) {
-
- unsigned NumToScan = 6;
- while (ScanFrom != ScanBB->begin()) {
- // Don't scan huge blocks.
- if (--NumToScan == 0) return 0;
-
- Instruction *Inst = --ScanFrom;
-
- // If this is a load of Ptr, the loaded value is available.
- if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
- if (LI->getOperand(0) == Ptr)
- return LI;
-
- if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
- // If this is a store through Ptr, the value is available!
- if (SI->getOperand(1) == Ptr)
- return SI->getOperand(0);
-
- // If Ptr is an alloca and this is a store to a different alloca, ignore
- // the store. This is a trivial form of alias analysis that is important
- // for reg2mem'd code.
- if ((isa<AllocaInst>(Ptr) || isa<GlobalVariable>(Ptr)) &&
- (isa<AllocaInst>(SI->getOperand(1)) ||
- isa<GlobalVariable>(SI->getOperand(1))))
- continue;
-
- // Otherwise the store that may or may not alias the pointer, bail out.
- ++ScanFrom;
- return 0;
- }
-
-
- // If this is some other instruction that may clobber Ptr, bail out.
- if (Inst->mayWriteToMemory()) {
- // May modify the pointer, bail out.
- ++ScanFrom;
- return 0;
- }
- }
-
- // Got to the start of the block, we didn't find it, but are done for this
- // block.
- return 0;
-}
-
-
/// SimplifyPartiallyRedundantLoad - If LI is an obviously partially redundant
/// load instruction, eliminate it by replacing it with a PHI node. This is an
/// important optimization that encourages jump threading, and needs to be run
@@ -330,7 +269,8 @@
// the entry to its block.
BasicBlock::iterator BBIt = LI;
- if (Value *AvailableVal = FindAvailableLoadedValue(LoadedPtr, LoadBB, BBIt)) {
+ if (Value *AvailableVal = FindAvailableLoadedValue(LoadedPtr, LoadBB,
+ BBIt, 6)) {
// If the value if the load is locally available within the block, just use
// it. This frequently occurs for reg2mem'd allocas.
//cerr << "LOAD ELIMINATED:\n" << *BBIt << *LI << "\n";
@@ -363,7 +303,7 @@
// Scan the predecessor to see if the value is available in the pred.
BBIt = PredBB->end();
- Value *PredAvailable = FindAvailableLoadedValue(LoadedPtr, PredBB, BBIt);
+ Value *PredAvailable = FindAvailableLoadedValue(LoadedPtr, PredBB, BBIt, 6);
if (!PredAvailable) {
OneUnavailablePred = PredBB;
continue;
Modified: llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp?rev=60166&r1=60165&r2=60166&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp Thu Nov 27 02:10:05 2008
@@ -371,3 +371,65 @@
return NewBB;
}
+
+/// 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 *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
+ BasicBlock::iterator &ScanFrom,
+ unsigned MaxInstsToScan,
+ AliasAnalysis *AA) {
+ if (MaxInstsToScan == 0) MaxInstsToScan = ~0U;
+
+ while (ScanFrom != ScanBB->begin()) {
+ // Don't scan huge blocks.
+ if (MaxInstsToScan-- == 0) return 0;
+
+ Instruction *Inst = --ScanFrom;
+
+ // If this is a load of Ptr, the loaded value is available.
+ if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
+ if (LI->getOperand(0) == Ptr)
+ return LI;
+
+ if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ // If this is a store through Ptr, the value is available!
+ if (SI->getOperand(1) == Ptr)
+ return SI->getOperand(0);
+
+ // If Ptr is an alloca and this is a store to a different alloca, ignore
+ // the store. This is a trivial form of alias analysis that is important
+ // for reg2mem'd code.
+ if ((isa<AllocaInst>(Ptr) || isa<GlobalVariable>(Ptr)) &&
+ (isa<AllocaInst>(SI->getOperand(1)) ||
+ isa<GlobalVariable>(SI->getOperand(1))))
+ continue;
+
+ // Otherwise the store that may or may not alias the pointer, bail out.
+ ++ScanFrom;
+ return 0;
+ }
+
+
+ // If this is some other instruction that may clobber Ptr, bail out.
+ if (Inst->mayWriteToMemory()) {
+ // May modify the pointer, bail out.
+ ++ScanFrom;
+ return 0;
+ }
+ }
+
+ // Got to the start of the block, we didn't find it, but are done for this
+ // block.
+ return 0;
+}
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