R600: New control flow for SI v2
This patch replaces the control flow handling with a new
pass which structurize the graph before transforming it to
machine instruction. This has a couple of different advantages
and currently fixes 20 piglit tests without a single regression.
It is now a general purpose transformation that could be not
only be used for SI/R6xx, but also for other hardware
implementations that use a form of structurized control flow.
v2: further cleanup, fixes and documentation
Patch by: Christian König
Signed-off-by: Christian König <deathsimple@vodafone.de>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>
Tested-by: Michel Dänzer <michel.daenzer@amd.com>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170591 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/R600/SIAnnotateControlFlow.cpp b/lib/Target/R600/SIAnnotateControlFlow.cpp
new file mode 100644
index 0000000..d131835
--- /dev/null
+++ b/lib/Target/R600/SIAnnotateControlFlow.cpp
@@ -0,0 +1,337 @@
+//===-- SIAnnotateControlFlow.cpp - ------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// Annotates the control flow with hardware specific intrinsics.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+
+#include "llvm/Pass.h"
+#include "llvm/Module.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/Transforms/Utils/SSAUpdater.h"
+
+using namespace llvm;
+
+namespace {
+
+// Complex types used in this pass
+typedef std::pair<BasicBlock *, Value *> StackEntry;
+typedef SmallVector<StackEntry, 16> StackVector;
+
+// Intrinsic names the control flow is annotated with
+static const char *IfIntrinsic = "llvm.SI.if";
+static const char *ElseIntrinsic = "llvm.SI.else";
+static const char *BreakIntrinsic = "llvm.SI.break";
+static const char *IfBreakIntrinsic = "llvm.SI.if.break";
+static const char *ElseBreakIntrinsic = "llvm.SI.else.break";
+static const char *LoopIntrinsic = "llvm.SI.loop";
+static const char *EndCfIntrinsic = "llvm.SI.end.cf";
+
+class SIAnnotateControlFlow : public FunctionPass {
+
+ static char ID;
+
+ Type *Boolean;
+ Type *Void;
+ Type *Int64;
+ Type *ReturnStruct;
+
+ ConstantInt *BoolTrue;
+ ConstantInt *BoolFalse;
+ UndefValue *BoolUndef;
+ Constant *Int64Zero;
+
+ Constant *If;
+ Constant *Else;
+ Constant *Break;
+ Constant *IfBreak;
+ Constant *ElseBreak;
+ Constant *Loop;
+ Constant *EndCf;
+
+ DominatorTree *DT;
+ StackVector Stack;
+ SSAUpdater PhiInserter;
+
+ bool isTopOfStack(BasicBlock *BB);
+
+ Value *popSaved();
+
+ void push(BasicBlock *BB, Value *Saved);
+
+ bool isElse(PHINode *Phi);
+
+ void eraseIfUnused(PHINode *Phi);
+
+ void openIf(BranchInst *Term);
+
+ void insertElse(BranchInst *Term);
+
+ void handleLoopCondition(Value *Cond);
+
+ void handleLoop(BranchInst *Term);
+
+ void closeControlFlow(BasicBlock *BB);
+
+public:
+ SIAnnotateControlFlow():
+ FunctionPass(ID) { }
+
+ virtual bool doInitialization(Module &M);
+
+ virtual bool runOnFunction(Function &F);
+
+ virtual const char *getPassName() const {
+ return "SI annotate control flow";
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+
+ AU.addRequired<DominatorTree>();
+ AU.addPreserved<DominatorTree>();
+ FunctionPass::getAnalysisUsage(AU);
+ }
+
+};
+
+} // end anonymous namespace
+
+char SIAnnotateControlFlow::ID = 0;
+
+/// \brief Initialize all the types and constants used in the pass
+bool SIAnnotateControlFlow::doInitialization(Module &M) {
+
+ LLVMContext &Context = M.getContext();
+
+ Void = Type::getVoidTy(Context);
+ Boolean = Type::getInt1Ty(Context);
+ Int64 = Type::getInt64Ty(Context);
+ ReturnStruct = StructType::get(Boolean, Int64, (Type *)0);
+
+ BoolTrue = ConstantInt::getTrue(Context);
+ BoolFalse = ConstantInt::getFalse(Context);
+ BoolUndef = UndefValue::get(Boolean);
+ Int64Zero = ConstantInt::get(Int64, 0);
+
+ If = M.getOrInsertFunction(
+ IfIntrinsic, ReturnStruct, Boolean, (Type *)0);
+
+ Else = M.getOrInsertFunction(
+ ElseIntrinsic, ReturnStruct, Int64, (Type *)0);
+
+ Break = M.getOrInsertFunction(
+ BreakIntrinsic, Int64, Int64, (Type *)0);
+
+ IfBreak = M.getOrInsertFunction(
+ IfBreakIntrinsic, Int64, Boolean, Int64, (Type *)0);
+
+ ElseBreak = M.getOrInsertFunction(
+ ElseBreakIntrinsic, Int64, Int64, Int64, (Type *)0);
+
+ Loop = M.getOrInsertFunction(
+ LoopIntrinsic, Boolean, Int64, (Type *)0);
+
+ EndCf = M.getOrInsertFunction(
+ EndCfIntrinsic, Void, Int64, (Type *)0);
+
+ return false;
+}
+
+/// \brief Is BB the last block saved on the stack ?
+bool SIAnnotateControlFlow::isTopOfStack(BasicBlock *BB) {
+ return Stack.back().first == BB;
+}
+
+/// \brief Pop the last saved value from the control flow stack
+Value *SIAnnotateControlFlow::popSaved() {
+ return Stack.pop_back_val().second;
+}
+
+/// \brief Push a BB and saved value to the control flow stack
+void SIAnnotateControlFlow::push(BasicBlock *BB, Value *Saved) {
+ Stack.push_back(std::make_pair(BB, Saved));
+}
+
+/// \brief Can the condition represented by this PHI node treated like
+/// an "Else" block?
+bool SIAnnotateControlFlow::isElse(PHINode *Phi) {
+
+ BasicBlock *IDom = DT->getNode(Phi->getParent())->getIDom()->getBlock();
+ for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
+ if (Phi->getIncomingBlock(i) == IDom) {
+
+ if (Phi->getIncomingValue(i) != BoolTrue)
+ return false;
+
+ } else {
+ if (Phi->getIncomingValue(i) != BoolFalse)
+ return false;
+
+ }
+ }
+ return true;
+}
+
+// \brief Erase "Phi" if it is not used any more
+void SIAnnotateControlFlow::eraseIfUnused(PHINode *Phi) {
+ if (!Phi->hasNUsesOrMore(1))
+ Phi->eraseFromParent();
+}
+
+/// \brief Open a new "If" block
+void SIAnnotateControlFlow::openIf(BranchInst *Term) {
+ Value *Ret = CallInst::Create(If, Term->getCondition(), "", Term);
+ Term->setCondition(ExtractValueInst::Create(Ret, 0, "", Term));
+ push(Term->getSuccessor(1), ExtractValueInst::Create(Ret, 1, "", Term));
+}
+
+/// \brief Close the last "If" block and open a new "Else" block
+void SIAnnotateControlFlow::insertElse(BranchInst *Term) {
+ Value *Ret = CallInst::Create(Else, popSaved(), "", Term);
+ Term->setCondition(ExtractValueInst::Create(Ret, 0, "", Term));
+ push(Term->getSuccessor(1), ExtractValueInst::Create(Ret, 1, "", Term));
+}
+
+/// \brief Recursively handle the condition leading to a loop
+void SIAnnotateControlFlow::handleLoopCondition(Value *Cond) {
+
+ if (PHINode *Phi = dyn_cast<PHINode>(Cond)) {
+
+ // Handle all non constant incoming values first
+ for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
+ Value *Incoming = Phi->getIncomingValue(i);
+ if (isa<ConstantInt>(Incoming))
+ continue;
+
+ Phi->setIncomingValue(i, BoolFalse);
+ handleLoopCondition(Incoming);
+ }
+
+ BasicBlock *Parent = Phi->getParent();
+ BasicBlock *IDom = DT->getNode(Parent)->getIDom()->getBlock();
+
+ for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
+
+ Value *Incoming = Phi->getIncomingValue(i);
+ if (Incoming != BoolTrue)
+ continue;
+
+ BasicBlock *From = Phi->getIncomingBlock(i);
+ if (From == IDom) {
+ CallInst *OldEnd = dyn_cast<CallInst>(Parent->getFirstInsertionPt());
+ if (OldEnd && OldEnd->getCalledFunction() == EndCf) {
+ Value *Args[] = {
+ OldEnd->getArgOperand(0),
+ PhiInserter.GetValueAtEndOfBlock(Parent)
+ };
+ Value *Ret = CallInst::Create(ElseBreak, Args, "", OldEnd);
+ PhiInserter.AddAvailableValue(Parent, Ret);
+ continue;
+ }
+ }
+
+ TerminatorInst *Insert = From->getTerminator();
+ Value *Arg = PhiInserter.GetValueAtEndOfBlock(From);
+ Value *Ret = CallInst::Create(Break, Arg, "", Insert);
+ PhiInserter.AddAvailableValue(From, Ret);
+ }
+ eraseIfUnused(Phi);
+
+ } else if (Instruction *Inst = dyn_cast<Instruction>(Cond)) {
+ BasicBlock *Parent = Inst->getParent();
+ TerminatorInst *Insert = Parent->getTerminator();
+ Value *Args[] = { Cond, PhiInserter.GetValueAtEndOfBlock(Parent) };
+ Value *Ret = CallInst::Create(IfBreak, Args, "", Insert);
+ PhiInserter.AddAvailableValue(Parent, Ret);
+
+ } else {
+ assert(0 && "Unhandled loop condition!");
+ }
+}
+
+/// \brief Handle a back edge (loop)
+void SIAnnotateControlFlow::handleLoop(BranchInst *Term) {
+
+ BasicBlock *Target = Term->getSuccessor(1);
+ PHINode *Broken = PHINode::Create(Int64, 0, "", &Target->front());
+
+ PhiInserter.Initialize(Int64, "");
+ PhiInserter.AddAvailableValue(Target, Broken);
+
+ Value *Cond = Term->getCondition();
+ Term->setCondition(BoolTrue);
+ handleLoopCondition(Cond);
+
+ BasicBlock *BB = Term->getParent();
+ Value *Arg = PhiInserter.GetValueAtEndOfBlock(BB);
+ for (pred_iterator PI = pred_begin(Target), PE = pred_end(Target);
+ PI != PE; ++PI) {
+
+ Broken->addIncoming(*PI == BB ? Arg : Int64Zero, *PI);
+ }
+
+ Term->setCondition(CallInst::Create(Loop, Arg, "", Term));
+ push(Term->getSuccessor(0), Arg);
+}
+
+/// \brief Close the last opened control flow
+void SIAnnotateControlFlow::closeControlFlow(BasicBlock *BB) {
+ CallInst::Create(EndCf, popSaved(), "", BB->getFirstInsertionPt());
+}
+
+/// \brief Annotate the control flow with intrinsics so the backend can
+/// recognize if/then/else and loops.
+bool SIAnnotateControlFlow::runOnFunction(Function &F) {
+
+ DT = &getAnalysis<DominatorTree>();
+
+ for (df_iterator<BasicBlock *> I = df_begin(&F.getEntryBlock()),
+ E = df_end(&F.getEntryBlock()); I != E; ++I) {
+
+ BranchInst *Term = dyn_cast<BranchInst>((*I)->getTerminator());
+
+ if (!Term || Term->isUnconditional()) {
+ if (isTopOfStack(*I))
+ closeControlFlow(*I);
+ continue;
+ }
+
+ if (I.nodeVisited(Term->getSuccessor(1))) {
+ if (isTopOfStack(*I))
+ closeControlFlow(*I);
+ handleLoop(Term);
+ continue;
+ }
+
+ if (isTopOfStack(*I)) {
+ PHINode *Phi = dyn_cast<PHINode>(Term->getCondition());
+ if (Phi && Phi->getParent() == *I && isElse(Phi)) {
+ insertElse(Term);
+ eraseIfUnused(Phi);
+ continue;
+ }
+ closeControlFlow(*I);
+ }
+ openIf(Term);
+ }
+
+ assert(Stack.empty());
+ return true;
+}
+
+/// \brief Create the annotation pass
+FunctionPass *llvm::createSIAnnotateControlFlowPass() {
+
+ return new SIAnnotateControlFlow();
+}