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Make the LoopRotate pass's maximum header size configurable both programmatically 

and via the command line, mirroring similar functionality in LoopUnroll.  In
situations where clients used custom unrolling thresholds, their intent could
previously be foiled by LoopRotate having a hardcoded threshold.

llvm-svn: 209617
This commit is contained in:
Owen Anderson 2014-05-26 08:58:51 +00:00
parent e145a7da87
commit 115aa160e6
2 changed files with 15 additions and 5 deletions
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2
llvm/include/llvm/Transforms/Scalar.h
View File

@ -155,7 +155,7 @@ Pass *createLoopRerollPass();
//
// LoopRotate - This pass is a simple loop rotating pass.
//
Pass *createLoopRotatePass();
Pass *createLoopRotatePass(int MaxHeaderSize = -1);
//===----------------------------------------------------------------------===//
//

18
llvm/lib/Transforms/Scalar/LoopRotation.cpp
View File

@ -23,6 +23,7 @@
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
@ -32,7 +33,9 @@ using namespace llvm;
#define DEBUG_TYPE "loop-rotate"
#define MAX_HEADER_SIZE 16
static cl::opt<unsigned>
DefaultRotationThreshold("rotation-max-header-size", cl::init(16), cl::Hidden,
cl::desc("The default maximum header size for automatic loop rotation"));
STATISTIC(NumRotated, "Number of loops rotated");
namespace {
@ -40,8 +43,12 @@ namespace {
class LoopRotate : public LoopPass {
public:
static char ID; // Pass ID, replacement for typeid
LoopRotate() : LoopPass(ID) {
LoopRotate(int SpecifiedMaxHeaderSize = -1) : LoopPass(ID) {
initializeLoopRotatePass(*PassRegistry::getPassRegistry());
if (SpecifiedMaxHeaderSize == -1)
MaxHeaderSize = DefaultRotationThreshold;
else
MaxHeaderSize = unsigned(SpecifiedMaxHeaderSize);
}
// LCSSA form makes instruction renaming easier.
@ -62,6 +69,7 @@ namespace {
bool rotateLoop(Loop *L, bool SimplifiedLatch);
private:
unsigned MaxHeaderSize;
LoopInfo *LI;
const TargetTransformInfo *TTI;
};
@ -75,7 +83,9 @@ INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
INITIALIZE_PASS_DEPENDENCY(LCSSA)
INITIALIZE_PASS_END(LoopRotate, "loop-rotate", "Rotate Loops", false, false)
Pass *llvm::createLoopRotatePass() { return new LoopRotate(); }
Pass *llvm::createLoopRotatePass(int MaxHeaderSize) {
return new LoopRotate(MaxHeaderSize);
}
/// Rotate Loop L as many times as possible. Return true if
/// the loop is rotated at least once.
@ -320,7 +330,7 @@ bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
<< " instructions: "; L->dump());
return false;
}
if (Metrics.NumInsts > MAX_HEADER_SIZE)
if (Metrics.NumInsts > MaxHeaderSize)
return false;
}