[llvm-commits] CVS: llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
Chris Lattner
lattner at cs.uiuc.edu
Tue Dec 23 01:48:01 PST 2003
Changes in directory llvm/lib/Transforms/Scalar:
IndVarSimplify.cpp updated: 1.50 -> 1.51
---
Log message:
More minor non-functional changes. This now computes the exit condition, though
it doesn't do anything with it.
---
Diffs of the changes: (+52 -15)
Index: llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
diff -u llvm/lib/Transforms/Scalar/IndVarSimplify.cpp:1.50 llvm/lib/Transforms/Scalar/IndVarSimplify.cpp:1.51
--- llvm/lib/Transforms/Scalar/IndVarSimplify.cpp:1.50 Mon Dec 22 03:53:29 2003
+++ llvm/lib/Transforms/Scalar/IndVarSimplify.cpp Tue Dec 23 01:47:09 2003
@@ -14,6 +14,7 @@
//
//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "indvar"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/Type.h"
@@ -34,15 +35,16 @@
class IndVarSimplify : public FunctionPass {
LoopInfo *Loops;
TargetData *TD;
+ bool Changed;
public:
virtual bool runOnFunction(Function &) {
Loops = &getAnalysis<LoopInfo>();
TD = &getAnalysis<TargetData>();
-
+ Changed = false;
+
// Induction Variables live in the header nodes of loops
- bool Changed = false;
for (unsigned i = 0, e = Loops->getTopLevelLoops().size(); i != e; ++i)
- Changed |= runOnLoop(Loops->getTopLevelLoops()[i]);
+ runOnLoop(Loops->getTopLevelLoops()[i]);
return Changed;
}
@@ -55,7 +57,7 @@
Value *ComputeAuxIndVarValue(InductionVariable &IV, Value *CIV);
void ReplaceIndVar(InductionVariable &IV, Value *Counter);
- bool runOnLoop(Loop *L);
+ void runOnLoop(Loop *L);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<TargetData>(); // Need pointer size
@@ -73,11 +75,10 @@
}
-bool IndVarSimplify::runOnLoop(Loop *Loop) {
+void IndVarSimplify::runOnLoop(Loop *Loop) {
// Transform all subloops before this loop...
- bool Changed = false;
for (unsigned i = 0, e = Loop->getSubLoops().size(); i != e; ++i)
- Changed |= runOnLoop(Loop->getSubLoops()[i]);
+ runOnLoop(Loop->getSubLoops()[i]);
// Get the header node for this loop. All of the phi nodes that could be
// induction variables must live in this basic block.
@@ -95,7 +96,7 @@
// AfterPHIIt now points to first non-phi instruction...
// If there are no phi nodes in this basic block, there can't be indvars...
- if (IndVars.empty()) return Changed;
+ if (IndVars.empty()) return;
// Loop over the induction variables, looking for a canonical induction
// variable, and checking to make sure they are not all unknown induction
@@ -125,7 +126,42 @@
}
// No induction variables, bail early... don't add a canonical indvar
- if (MaxSize == 0) return Changed;
+ if (MaxSize == 0) return;
+
+
+ // Figure out what the exit condition of the loop is. We can currently only
+ // handle loops with a single exit. If we cannot figure out what the
+ // termination condition is, we leave this variable set to null.
+ //
+ SetCondInst *TermCond = 0;
+ if (Loop->getExitBlocks().size() == 1) {
+ // Get ExitingBlock - the basic block in the loop which contains the branch
+ // out of the loop.
+ BasicBlock *Exit = Loop->getExitBlocks()[0];
+ pred_iterator PI = pred_begin(Exit);
+ assert(PI != pred_end(Exit) && "Should have one predecessor in loop!");
+ BasicBlock *ExitingBlock = *PI;
+ assert(++PI == pred_end(Exit) && "Exit block should have one pred!");
+ assert(Loop->isLoopExit(ExitingBlock) && "Exiting block is not loop exit!");
+
+ // Since the block is in the loop, yet branches out of it, we know that the
+ // block must end with multiple destination terminator. Which means it is
+ // either a conditional branch, a switch instruction, or an invoke.
+ if (BranchInst *BI = dyn_cast<BranchInst>(ExitingBlock->getTerminator())) {
+ assert(BI->isConditional() && "Unconditional branch has multiple succs?");
+ TermCond = dyn_cast<SetCondInst>(BI->getCondition());
+ } else {
+ // NOTE: if people actually exit loops with switch instructions, we could
+ // handle them, but I don't think this is important enough to spend time
+ // thinking about.
+ assert(isa<SwitchInst>(ExitingBlock->getTerminator()) ||
+ isa<InvokeInst>(ExitingBlock->getTerminator()) &&
+ "Unknown multi-successor terminator!");
+ }
+ }
+
+ if (TermCond)
+ DEBUG(std::cerr << "INDVAR: Found termination condition: " << *TermCond);
// Okay, we want to convert other induction variables to use a canonical
// indvar. If we don't have one, add one now...
@@ -172,15 +208,18 @@
Canonical = &IndVars.back();
++NumInserted;
Changed = true;
+ DEBUG(std::cerr << "INDVAR: Inserted canonical iv: " << *PN);
} else {
// If we have a canonical induction variable, make sure that it is the first
// one in the basic block.
if (&Header->front() != Canonical->Phi)
Header->getInstList().splice(Header->begin(), Header->getInstList(),
Canonical->Phi);
+ DEBUG(std::cerr << "IndVar: Existing canonical iv used: "
+ << *Canonical->Phi);
}
- DEBUG(std::cerr << "Induction variables:\n");
+ DEBUG(std::cerr << "INDVAR: Replacing Induction variables:\n");
// Get the current loop iteration count, which is always the value of the
// canonical phi node...
@@ -202,8 +241,6 @@
++NumRemoved;
}
}
-
- return Changed;
}
/// ComputeAuxIndVarValue - Given an auxillary induction variable, compute and
@@ -269,7 +306,6 @@
return Val;
}
-
// ReplaceIndVar - Replace all uses of the specified induction variable with
// expressions computed from the specified loop iteration counter variable.
// Return true if instructions were deleted.
@@ -286,8 +322,9 @@
PHIOps.push_back(Phi->getIncomingValue(0));
PHIOps.push_back(Phi->getIncomingValue(1));
- // Delete all of the operands of the PHI node... FIXME, this should be more
- // intelligent.
+ // Delete all of the operands of the PHI node... so that the to-be-deleted PHI
+ // node does not cause any expressions to be computed that would not otherwise
+ // be.
Phi->dropAllReferences();
// Now that we are rid of unneeded uses of the PHI node, replace any remaining
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