[llvm-commits] [llvm] r83755 - /llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
Chris Lattner
sabre at nondot.org
Sat Oct 10 21:33:43 PDT 2009
Author: lattner
Date: Sat Oct 10 23:33:43 2009
New Revision: 83755
URL: http://llvm.org/viewvc/llvm-project?rev=83755&view=rev
Log:
factor some code better and move a function, no functionality change.
Modified:
llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=83755&r1=83754&r2=83755&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Sat Oct 10 23:33:43 2009
@@ -74,8 +74,7 @@
void FindLoopHeaders(Function &F);
bool ProcessBlock(BasicBlock *BB);
- bool ThreadEdge(BasicBlock *BB, BasicBlock *PredBB, BasicBlock *SuccBB,
- unsigned JumpThreadCost);
+ bool ThreadEdge(BasicBlock *BB, BasicBlock *PredBB, BasicBlock *SuccBB);
BasicBlock *FactorCommonPHIPreds(PHINode *PN, Value *Val);
bool ProcessBranchOnDuplicateCond(BasicBlock *PredBB, BasicBlock *DestBB);
bool ProcessSwitchOnDuplicateCond(BasicBlock *PredBB, BasicBlock *DestBB);
@@ -180,46 +179,6 @@
}
-/// getJumpThreadDuplicationCost - Return the cost of duplicating this block to
-/// thread across it.
-static unsigned getJumpThreadDuplicationCost(const BasicBlock *BB) {
- /// Ignore PHI nodes, these will be flattened when duplication happens.
- BasicBlock::const_iterator I = BB->getFirstNonPHI();
-
- // Sum up the cost of each instruction until we get to the terminator. Don't
- // include the terminator because the copy won't include it.
- unsigned Size = 0;
- for (; !isa<TerminatorInst>(I); ++I) {
- // Debugger intrinsics don't incur code size.
- if (isa<DbgInfoIntrinsic>(I)) continue;
-
- // If this is a pointer->pointer bitcast, it is free.
- if (isa<BitCastInst>(I) && isa<PointerType>(I->getType()))
- continue;
-
- // All other instructions count for at least one unit.
- ++Size;
-
- // Calls are more expensive. If they are non-intrinsic calls, we model them
- // as having cost of 4. If they are a non-vector intrinsic, we model them
- // as having cost of 2 total, and if they are a vector intrinsic, we model
- // them as having cost 1.
- if (const CallInst *CI = dyn_cast<CallInst>(I)) {
- if (!isa<IntrinsicInst>(CI))
- Size += 3;
- else if (!isa<VectorType>(CI->getType()))
- Size += 1;
- }
- }
-
- // Threading through a switch statement is particularly profitable. If this
- // block ends in a switch, decrease its cost to make it more likely to happen.
- if (isa<SwitchInst>(I))
- Size = Size > 6 ? Size-6 : 0;
-
- return Size;
-}
-
/// GetBestDestForBranchOnUndef - If we determine that the specified block ends
/// in an undefined jump, decide which block is best to revector to.
///
@@ -450,21 +409,13 @@
ConstantFoldTerminator(BB);
return true;
}
-
- // Otherwise we need to thread from PredBB to DestBB's successor which
- // involves code duplication. Check to see if it is worth it.
- unsigned JumpThreadCost = getJumpThreadDuplicationCost(BB);
- if (JumpThreadCost > Threshold) {
- DEBUG(errs() << " Not threading BB '" << BB->getName()
- << "' - Cost is too high: " << JumpThreadCost << "\n");
- return false;
- }
+
// Next, figure out which successor we are threading to.
BasicBlock *SuccBB = DestBI->getSuccessor(!BranchDir);
// Ok, try to thread it!
- return ThreadEdge(BB, PredBB, SuccBB, JumpThreadCost);
+ return ThreadEdge(BB, PredBB, SuccBB);
}
/// ProcessSwitchOnDuplicateCond - We found a block and a predecessor of that
@@ -724,18 +675,11 @@
// See if the cost of duplicating this block is low enough.
BasicBlock *BB = PN->getParent();
- unsigned JumpThreadCost = getJumpThreadDuplicationCost(BB);
- if (JumpThreadCost > Threshold) {
- DEBUG(errs() << " Not threading BB '" << BB->getName()
- << "' - Cost is too high: " << JumpThreadCost << "\n");
- return false;
- }
// If so, we can actually do this threading. Merge any common predecessors
// that will act the same.
BasicBlock *PredBB = FactorCommonPHIPreds(PN, PredCst);
-
-
+
TerminatorInst *BBTerm = BB->getTerminator();
// Next, figure out which successor we are threading to.
@@ -751,7 +695,7 @@
}
// Ok, try to thread it!
- return ThreadEdge(BB, PredBB, SuccBB, JumpThreadCost);
+ return ThreadEdge(BB, PredBB, SuccBB);
}
/// ProcessJumpOnLogicalPHI - PN's basic block contains a conditional branch
@@ -795,14 +739,6 @@
if (PredNo == ~0U)
return false;
- // See if the cost of duplicating this block is low enough.
- unsigned JumpThreadCost = getJumpThreadDuplicationCost(BB);
- if (JumpThreadCost > Threshold) {
- DEBUG(errs() << " Not threading BB '" << BB->getName()
- << "' - Cost is too high: " << JumpThreadCost << "\n");
- return false;
- }
-
// If so, we can actually do this threading. Merge any common predecessors
// that will act the same.
BasicBlock *PredBB = FactorCommonPHIPreds(PN, PredCst);
@@ -814,7 +750,7 @@
BasicBlock *SuccBB = BB->getTerminator()->getSuccessor(isAnd);
// Ok, try to thread it!
- return ThreadEdge(BB, PredBB, SuccBB, JumpThreadCost);
+ return ThreadEdge(BB, PredBB, SuccBB);
}
/// GetResultOfComparison - Given an icmp/fcmp predicate and the left and right
@@ -881,14 +817,6 @@
if (PredVal == 0)
return false;
- // See if the cost of duplicating this block is low enough.
- unsigned JumpThreadCost = getJumpThreadDuplicationCost(BB);
- if (JumpThreadCost > Threshold) {
- DEBUG(errs() << " Not threading BB '" << BB->getName()
- << "' - Cost is too high: " << JumpThreadCost << "\n");
- return false;
- }
-
// If so, we can actually do this threading. Merge any common predecessors
// that will act the same.
BasicBlock *PredBB = FactorCommonPHIPreds(PN, PredVal);
@@ -897,7 +825,47 @@
BasicBlock *SuccBB = BB->getTerminator()->getSuccessor(!TrueDirection);
// Ok, try to thread it!
- return ThreadEdge(BB, PredBB, SuccBB, JumpThreadCost);
+ return ThreadEdge(BB, PredBB, SuccBB);
+}
+
+/// getJumpThreadDuplicationCost - Return the cost of duplicating this block to
+/// thread across it.
+static unsigned getJumpThreadDuplicationCost(const BasicBlock *BB) {
+ /// Ignore PHI nodes, these will be flattened when duplication happens.
+ BasicBlock::const_iterator I = BB->getFirstNonPHI();
+
+ // Sum up the cost of each instruction until we get to the terminator. Don't
+ // include the terminator because the copy won't include it.
+ unsigned Size = 0;
+ for (; !isa<TerminatorInst>(I); ++I) {
+ // Debugger intrinsics don't incur code size.
+ if (isa<DbgInfoIntrinsic>(I)) continue;
+
+ // If this is a pointer->pointer bitcast, it is free.
+ if (isa<BitCastInst>(I) && isa<PointerType>(I->getType()))
+ continue;
+
+ // All other instructions count for at least one unit.
+ ++Size;
+
+ // Calls are more expensive. If they are non-intrinsic calls, we model them
+ // as having cost of 4. If they are a non-vector intrinsic, we model them
+ // as having cost of 2 total, and if they are a vector intrinsic, we model
+ // them as having cost 1.
+ if (const CallInst *CI = dyn_cast<CallInst>(I)) {
+ if (!isa<IntrinsicInst>(CI))
+ Size += 3;
+ else if (!isa<VectorType>(CI->getType()))
+ Size += 1;
+ }
+ }
+
+ // Threading through a switch statement is particularly profitable. If this
+ // block ends in a switch, decrease its cost to make it more likely to happen.
+ if (isa<SwitchInst>(I))
+ Size = Size > 6 ? Size-6 : 0;
+
+ return Size;
}
@@ -905,8 +873,14 @@
/// edge from PredBB to SuccBB across BB. Transform the IR to reflect this
/// change.
bool JumpThreading::ThreadEdge(BasicBlock *BB, BasicBlock *PredBB,
- BasicBlock *SuccBB, unsigned JumpThreadCost) {
-
+ BasicBlock *SuccBB) {
+ unsigned JumpThreadCost = getJumpThreadDuplicationCost(BB);
+ if (JumpThreadCost > Threshold) {
+ DEBUG(errs() << " Not threading BB '" << BB->getName()
+ << "' - Cost is too high: " << JumpThreadCost << "\n");
+ return false;
+ }
+
// If threading to the same block as we come from, we would infinite loop.
if (SuccBB == BB) {
DEBUG(errs() << " Not threading across BB '" << BB->getName()
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