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-rw-r--r--llvm/include/llvm/InitializePasses.h2
-rw-r--r--llvm/include/llvm/Transforms/Scalar/SpeculativeExecution.h92
-rw-r--r--llvm/lib/Passes/PassBuilder.cpp1
-rw-r--r--llvm/lib/Passes/PassRegistry.def1
-rw-r--r--llvm/lib/Transforms/Scalar/Scalar.cpp2
-rw-r--r--llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp96
-rw-r--r--llvm/test/Transforms/SpeculativeExecution/spec.ll3
7 files changed, 156 insertions, 41 deletions
diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h
index e0bb575ae2f..b9a699d40d0 100644
--- a/llvm/include/llvm/InitializePasses.h
+++ b/llvm/include/llvm/InitializePasses.h
@@ -313,7 +313,7 @@ void initializeSingleLoopExtractorPass(PassRegistry&);
void initializeSinkingLegacyPassPass(PassRegistry&);
void initializeSjLjEHPreparePass(PassRegistry&);
void initializeSlotIndexesPass(PassRegistry&);
-void initializeSpeculativeExecutionPass(PassRegistry&);
+void initializeSpeculativeExecutionLegacyPassPass(PassRegistry&);
void initializeSpillPlacementPass(PassRegistry&);
void initializeStackColoringPass(PassRegistry&);
void initializeStackMapLivenessPass(PassRegistry&);
diff --git a/llvm/include/llvm/Transforms/Scalar/SpeculativeExecution.h b/llvm/include/llvm/Transforms/Scalar/SpeculativeExecution.h
new file mode 100644
index 00000000000..068f81776a0
--- /dev/null
+++ b/llvm/include/llvm/Transforms/Scalar/SpeculativeExecution.h
@@ -0,0 +1,92 @@
+//===- SpeculativeExecution.h -----------------------------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass hoists instructions to enable speculative execution on
+// targets where branches are expensive. This is aimed at GPUs. It
+// currently works on simple if-then and if-then-else
+// patterns.
+//
+// Removing branches is not the only motivation for this
+// pass. E.g. consider this code and assume that there is no
+// addressing mode for multiplying by sizeof(*a):
+//
+// if (b > 0)
+// c = a[i + 1]
+// if (d > 0)
+// e = a[i + 2]
+//
+// turns into
+//
+// p = &a[i + 1];
+// if (b > 0)
+// c = *p;
+// q = &a[i + 2];
+// if (d > 0)
+// e = *q;
+//
+// which could later be optimized to
+//
+// r = &a[i];
+// if (b > 0)
+// c = r[1];
+// if (d > 0)
+// e = r[2];
+//
+// Later passes sink back much of the speculated code that did not enable
+// further optimization.
+//
+// This pass is more aggressive than the function SpeculativeyExecuteBB in
+// SimplifyCFG. SimplifyCFG will not speculate if no selects are introduced and
+// it will speculate at most one instruction. It also will not speculate if
+// there is a value defined in the if-block that is only used in the then-block.
+// These restrictions make sense since the speculation in SimplifyCFG seems
+// aimed at introducing cheap selects, while this pass is intended to do more
+// aggressive speculation while counting on later passes to either capitalize on
+// that or clean it up.
+//
+// If the pass was created by calling
+// createSpeculativeExecutionIfHasBranchDivergencePass or the
+// -spec-exec-only-if-divergent-target option is present, this pass only has an
+// effect on targets where TargetTransformInfo::hasBranchDivergence() is true;
+// on other targets, it is a nop.
+//
+// This lets you include this pass unconditionally in the IR pass pipeline, but
+// only enable it for relevant targets.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_TRANSFORMS_SCALAR_SPECULATIVEEXECUTION_H
+#define LLVM_TRANSFORMS_SCALAR_SPECULATIVEEXECUTION_H
+
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+class SpeculativeExecutionPass
+ : public PassInfoMixin<SpeculativeExecutionPass> {
+public:
+ SpeculativeExecutionPass(bool OnlyIfDivergentTarget = false);
+
+ PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
+
+ // Glue for old PM
+ bool runImpl(Function &F, TargetTransformInfo *TTI);
+
+private:
+ bool runOnBasicBlock(BasicBlock &B);
+ bool considerHoistingFromTo(BasicBlock &FromBlock, BasicBlock &ToBlock);
+
+ // If true, this pass is a nop unless the target architecture has branch
+ // divergence.
+ const bool OnlyIfDivergentTarget = false;
+
+ TargetTransformInfo *TTI = nullptr;
+};
+}
+
+#endif //LLVM_TRANSFORMS_SCALAR_SPECULATIVEEXECUTION_H
diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
index 44ac46f3dae..6b994ff5b60 100644
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -112,6 +112,7 @@
#include "llvm/Transforms/Scalar/SROA.h"
#include "llvm/Transforms/Scalar/SimplifyCFG.h"
#include "llvm/Transforms/Scalar/Sink.h"
+#include "llvm/Transforms/Scalar/SpeculativeExecution.h"
#include "llvm/Transforms/Scalar/TailRecursionElimination.h"
#include "llvm/Transforms/Utils/AddDiscriminators.h"
#include "llvm/Transforms/Utils/BreakCriticalEdges.h"
diff --git a/llvm/lib/Passes/PassRegistry.def b/llvm/lib/Passes/PassRegistry.def
index 86ff8fae9ae..76672227540 100644
--- a/llvm/lib/Passes/PassRegistry.def
+++ b/llvm/lib/Passes/PassRegistry.def
@@ -175,6 +175,7 @@ FUNCTION_PASS("sccp", SCCPPass())
FUNCTION_PASS("simplify-cfg", SimplifyCFGPass())
FUNCTION_PASS("sink", SinkingPass())
FUNCTION_PASS("slp-vectorizer", SLPVectorizerPass())
+FUNCTION_PASS("speculative-execution", SpeculativeExecutionPass())
FUNCTION_PASS("sroa", SROA())
FUNCTION_PASS("tailcallelim", TailCallElimPass())
FUNCTION_PASS("unreachableblockelim", UnreachableBlockElimPass())
diff --git a/llvm/lib/Transforms/Scalar/Scalar.cpp b/llvm/lib/Transforms/Scalar/Scalar.cpp
index a122984fcf7..4cc61d64647 100644
--- a/llvm/lib/Transforms/Scalar/Scalar.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -80,7 +80,7 @@ void llvm::initializeScalarOpts(PassRegistry &Registry) {
initializeSinkingLegacyPassPass(Registry);
initializeTailCallElimPass(Registry);
initializeSeparateConstOffsetFromGEPPass(Registry);
- initializeSpeculativeExecutionPass(Registry);
+ initializeSpeculativeExecutionLegacyPassPass(Registry);
initializeStraightLineStrengthReducePass(Registry);
initializeLoadCombinePass(Registry);
initializePlaceBackedgeSafepointsImplPass(Registry);
diff --git a/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp b/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
index 9bf2d620681..b33ca5cbc99 100644
--- a/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
+++ b/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
@@ -61,9 +61,9 @@
//
//===----------------------------------------------------------------------===//
+#include "llvm/Transforms/Scalar/SpeculativeExecution.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/Analysis/GlobalsModRef.h"
-#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
@@ -101,58 +101,62 @@ static cl::opt<bool> SpecExecOnlyIfDivergentTarget(
namespace {
-class SpeculativeExecution : public FunctionPass {
- public:
- static char ID;
- explicit SpeculativeExecution(bool OnlyIfDivergentTarget = false)
- : FunctionPass(ID),
- OnlyIfDivergentTarget(OnlyIfDivergentTarget ||
- SpecExecOnlyIfDivergentTarget) {}
-
- void getAnalysisUsage(AnalysisUsage &AU) const override;
- bool runOnFunction(Function &F) override;
-
- const char *getPassName() const override {
- if (OnlyIfDivergentTarget)
- return "Speculatively execute instructions if target has divergent "
- "branches";
- return "Speculatively execute instructions";
- }
-
- private:
- bool runOnBasicBlock(BasicBlock &B);
- bool considerHoistingFromTo(BasicBlock &FromBlock, BasicBlock &ToBlock);
-
- // If true, this pass is a nop unless the target architecture has branch
- // divergence.
+class SpeculativeExecutionLegacyPass : public FunctionPass {
+public:
+ static char ID;
+ explicit SpeculativeExecutionLegacyPass(bool OnlyIfDivergentTarget = false)
+ : FunctionPass(ID), OnlyIfDivergentTarget(OnlyIfDivergentTarget ||
+ SpecExecOnlyIfDivergentTarget),
+ Impl(OnlyIfDivergentTarget) {}
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+ bool runOnFunction(Function &F) override;
+
+ const char *getPassName() const override {
+ if (OnlyIfDivergentTarget)
+ return "Speculatively execute instructions if target has divergent "
+ "branches";
+ return "Speculatively execute instructions";
+ }
+
+private:
+ // Variable preserved purely for correct name printing.
const bool OnlyIfDivergentTarget;
- const TargetTransformInfo *TTI = nullptr;
+
+ SpeculativeExecutionPass Impl;
};
} // namespace
-char SpeculativeExecution::ID = 0;
-INITIALIZE_PASS_BEGIN(SpeculativeExecution, "speculative-execution",
+char SpeculativeExecutionLegacyPass::ID = 0;
+INITIALIZE_PASS_BEGIN(SpeculativeExecutionLegacyPass, "speculative-execution",
"Speculatively execute instructions", false, false)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
-INITIALIZE_PASS_END(SpeculativeExecution, "speculative-execution",
+INITIALIZE_PASS_END(SpeculativeExecutionLegacyPass, "speculative-execution",
"Speculatively execute instructions", false, false)
-void SpeculativeExecution::getAnalysisUsage(AnalysisUsage &AU) const {
+void SpeculativeExecutionLegacyPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<TargetTransformInfoWrapperPass>();
AU.addPreserved<GlobalsAAWrapperPass>();
}
-bool SpeculativeExecution::runOnFunction(Function &F) {
+bool SpeculativeExecutionLegacyPass::runOnFunction(Function &F) {
if (skipFunction(F))
return false;
- TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
+ auto *TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
+ return Impl.runImpl(F, TTI);
+}
+
+namespace llvm {
+
+bool SpeculativeExecutionPass::runImpl(Function &F, TargetTransformInfo *TTI) {
if (OnlyIfDivergentTarget && !TTI->hasBranchDivergence()) {
DEBUG(dbgs() << "Not running SpeculativeExecution because "
"TTI->hasBranchDivergence() is false.\n");
return false;
}
+ this->TTI = TTI;
bool Changed = false;
for (auto& B : F) {
Changed |= runOnBasicBlock(B);
@@ -160,7 +164,7 @@ bool SpeculativeExecution::runOnFunction(Function &F) {
return Changed;
}
-bool SpeculativeExecution::runOnBasicBlock(BasicBlock &B) {
+bool SpeculativeExecutionPass::runOnBasicBlock(BasicBlock &B) {
BranchInst *BI = dyn_cast<BranchInst>(B.getTerminator());
if (BI == nullptr)
return false;
@@ -227,8 +231,8 @@ static unsigned ComputeSpeculationCost(const Instruction *I,
}
}
-bool SpeculativeExecution::considerHoistingFromTo(BasicBlock &FromBlock,
- BasicBlock &ToBlock) {
+bool SpeculativeExecutionPass::considerHoistingFromTo(
+ BasicBlock &FromBlock, BasicBlock &ToBlock) {
SmallSet<const Instruction *, 8> NotHoisted;
const auto AllPrecedingUsesFromBlockHoisted = [&NotHoisted](User *U) {
for (Value* V : U->operand_values()) {
@@ -270,14 +274,28 @@ bool SpeculativeExecution::considerHoistingFromTo(BasicBlock &FromBlock,
return true;
}
-namespace llvm {
-
FunctionPass *createSpeculativeExecutionPass() {
- return new SpeculativeExecution();
+ return new SpeculativeExecutionLegacyPass();
}
FunctionPass *createSpeculativeExecutionIfHasBranchDivergencePass() {
- return new SpeculativeExecution(/* OnlyIfDivergentTarget = */ true);
+ return new SpeculativeExecutionLegacyPass(/* OnlyIfDivergentTarget = */ true);
}
+SpeculativeExecutionPass::SpeculativeExecutionPass(bool OnlyIfDivergentTarget)
+ : OnlyIfDivergentTarget(OnlyIfDivergentTarget ||
+ SpecExecOnlyIfDivergentTarget) {}
+
+PreservedAnalyses SpeculativeExecutionPass::run(Function &F,
+ FunctionAnalysisManager &AM) {
+ auto *TTI = &AM.getResult<TargetIRAnalysis>(F);
+
+ bool Changed = runImpl(F, TTI);
+
+ if (!Changed)
+ return PreservedAnalyses::all();
+ PreservedAnalyses PA;
+ PA.preserve<GlobalsAA>();
+ return PA;
+}
} // namespace llvm
diff --git a/llvm/test/Transforms/SpeculativeExecution/spec.ll b/llvm/test/Transforms/SpeculativeExecution/spec.ll
index b0953c85dd4..0aa718f031a 100644
--- a/llvm/test/Transforms/SpeculativeExecution/spec.ll
+++ b/llvm/test/Transforms/SpeculativeExecution/spec.ll
@@ -1,6 +1,9 @@
; RUN: opt < %s -S -speculative-execution \
; RUN: -spec-exec-max-speculation-cost 4 -spec-exec-max-not-hoisted 3 \
; RUN: | FileCheck %s
+; RUN: opt < %s -S -passes='speculative-execution' \
+; RUN: -spec-exec-max-speculation-cost 4 -spec-exec-max-not-hoisted 3 \
+; RUN: | FileCheck %s
target datalayout = "e-i64:64-v16:16-v32:32-n16:32:64"
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