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

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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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209617 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2014-05-26 08:58:51 +00:00
parent bcc96923e0
commit 866ed7f63f
2 changed files with 15 additions and 5 deletions
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2
include/llvm/Transforms/Scalar.h
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@ -155,7 +155,7 @@ Pass *createLoopRerollPass();
// //
// LoopRotate - This pass is a simple loop rotating pass. // LoopRotate - This pass is a simple loop rotating pass.
// //
Pass *createLoopRotatePass(); Pass *createLoopRotatePass(int MaxHeaderSize = -1);
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
// //

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

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