[llvm] b99c91a - [NFC][SCEV] Piping to pass new SCEVCheapExpansionBudget option into SCEVExpander::isHighCostExpansionHelper()
Roman Lebedev via llvm-commits
llvm-commits at lists.llvm.org
Tue Feb 25 12:06:59 PST 2020
Author: Roman Lebedev
Date: 2020-02-25T23:05:57+03:00
New Revision: b99c91a0872f4b7b7e482c40818bbdda4c967bd5
URL: https://github.com/llvm/llvm-project/commit/b99c91a0872f4b7b7e482c40818bbdda4c967bd5
DIFF: https://github.com/llvm/llvm-project/commit/b99c91a0872f4b7b7e482c40818bbdda4c967bd5.diff
LOG: [NFC][SCEV] Piping to pass new SCEVCheapExpansionBudget option into SCEVExpander::isHighCostExpansionHelper()
Summary:
In future patches`SCEVExpander::isHighCostExpansionHelper()` will respect the budget allocated by performing TTI cost modelling.
This is a fully NFC patch to make things reviewable.
Reviewers: reames, mkazantsev, wmi, sanjoy
Reviewed By: mkazantsev
Subscribers: hiraditya, zzheng, javed.absar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D73705
Added:
Modified:
llvm/include/llvm/Analysis/ScalarEvolutionExpander.h
llvm/lib/Analysis/ScalarEvolutionExpander.cpp
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
llvm/lib/Transforms/Utils/LoopUtils.cpp
llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/Analysis/ScalarEvolutionExpander.h b/llvm/include/llvm/Analysis/ScalarEvolutionExpander.h
index 3f00b71c1c12..a1b2ed3666c7 100644
--- a/llvm/include/llvm/Analysis/ScalarEvolutionExpander.h
+++ b/llvm/include/llvm/Analysis/ScalarEvolutionExpander.h
@@ -19,11 +19,13 @@
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ScalarEvolutionNormalization.h"
#include "llvm/Analysis/TargetFolder.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/ValueHandle.h"
+#include "llvm/Support/CommandLine.h"
namespace llvm {
- class TargetTransformInfo;
+ extern cl::opt<unsigned> SCEVCheapExpansionBudget;
/// Return true if the given expression is safe to expand in the sense that
/// all materialized values are safe to speculate anywhere their operands are
@@ -177,11 +179,13 @@ namespace llvm {
/// At is an optional parameter which specifies point in code where user is
/// going to expand this expression. Sometimes this knowledge can lead to a
/// more accurate cost estimation.
- bool isHighCostExpansion(const SCEV *Expr, Loop *L,
+ bool isHighCostExpansion(const SCEV *Expr, Loop *L, unsigned Budget,
const TargetTransformInfo *TTI,
const Instruction *At = nullptr) {
SmallPtrSet<const SCEV *, 8> Processed;
- return isHighCostExpansionHelper(Expr, L, At, TTI, Processed);
+ int BudgetRemaining = Budget * TargetTransformInfo::TCC_Basic;
+ return isHighCostExpansionHelper(Expr, L, At, BudgetRemaining, TTI,
+ Processed);
}
/// This method returns the canonical induction variable of the specified
@@ -324,7 +328,7 @@ namespace llvm {
/// Recursive helper function for isHighCostExpansion.
bool isHighCostExpansionHelper(const SCEV *S, Loop *L,
- const Instruction *At,
+ const Instruction *At, int &BudgetRemaining,
const TargetTransformInfo *TTI,
SmallPtrSetImpl<const SCEV *> &Processed);
diff --git a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
index c560eea14b86..146db097d6aa 100644
--- a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -24,10 +24,17 @@
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PatternMatch.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
+
+cl::opt<unsigned> llvm::SCEVCheapExpansionBudget(
+ "scev-cheap-expansion-budget", cl::Hidden, cl::init(4),
+ cl::desc("When performing SCEV expansion only if it is cheap to do, this "
+ "controls the budget that is considered cheap (default = 4)"));
+
using namespace PatternMatch;
/// ReuseOrCreateCast - Arrange for there to be a cast of V to Ty at IP,
@@ -2129,7 +2136,7 @@ SCEVExpander::getRelatedExistingExpansion(const SCEV *S, const Instruction *At,
}
bool SCEVExpander::isHighCostExpansionHelper(
- const SCEV *S, Loop *L, const Instruction *At,
+ const SCEV *S, Loop *L, const Instruction *At, int &BudgetRemaining,
const TargetTransformInfo *TTI, SmallPtrSetImpl<const SCEV *> &Processed) {
// If we can find an existing value for this scev available at the point "At"
// then consider the expression cheap.
@@ -2143,13 +2150,13 @@ bool SCEVExpander::isHighCostExpansionHelper(
return false;
case scTruncate:
return isHighCostExpansionHelper(cast<SCEVTruncateExpr>(S)->getOperand(), L,
- At, TTI, Processed);
+ At, BudgetRemaining, TTI, Processed);
case scZeroExtend:
return isHighCostExpansionHelper(cast<SCEVZeroExtendExpr>(S)->getOperand(),
- L, At, TTI, Processed);
+ L, At, BudgetRemaining, TTI, Processed);
case scSignExtend:
return isHighCostExpansionHelper(cast<SCEVSignExtendExpr>(S)->getOperand(),
- L, At, TTI, Processed);
+ L, At, BudgetRemaining, TTI, Processed);
}
if (!Processed.insert(S).second)
@@ -2162,8 +2169,8 @@ bool SCEVExpander::isHighCostExpansionHelper(
// lowered into a right shift.
if (auto *SC = dyn_cast<SCEVConstant>(UDivExpr->getRHS()))
if (SC->getAPInt().isPowerOf2()) {
- if (isHighCostExpansionHelper(UDivExpr->getLHS(), L, At, TTI,
- Processed))
+ if (isHighCostExpansionHelper(UDivExpr->getLHS(), L, At,
+ BudgetRemaining, TTI, Processed))
return true;
const DataLayout &DL =
L->getHeader()->getParent()->getParent()->getDataLayout();
@@ -2200,7 +2207,7 @@ bool SCEVExpander::isHighCostExpansionHelper(
// they are not too expensive rematerialize.
if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(S)) {
for (auto *Op : NAry->operands())
- if (isHighCostExpansionHelper(Op, L, At, TTI, Processed))
+ if (isHighCostExpansionHelper(Op, L, At, BudgetRemaining, TTI, Processed))
return true;
}
diff --git a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
index e7055ef6baf8..e513070201e5 100644
--- a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -2759,7 +2759,8 @@ bool IndVarSimplify::run(Loop *L) {
// Avoid high cost expansions. Note: This heuristic is questionable in
// that our definition of "high cost" is not exactly principled.
- if (Rewriter.isHighCostExpansion(ExitCount, L, TTI))
+ if (Rewriter.isHighCostExpansion(ExitCount, L, SCEVCheapExpansionBudget,
+ TTI))
continue;
// Check preconditions for proper SCEVExpander operation. SCEV does not
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index c9cc511879db..b8f8cc35fa30 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -635,7 +635,8 @@ bool llvm::UnrollRuntimeLoopRemainder(
const DataLayout &DL = Header->getModule()->getDataLayout();
SCEVExpander Expander(*SE, DL, "loop-unroll");
if (!AllowExpensiveTripCount &&
- Expander.isHighCostExpansion(TripCountSC, L, TTI, PreHeaderBR)) {
+ Expander.isHighCostExpansion(TripCountSC, L, SCEVCheapExpansionBudget,
+ TTI, PreHeaderBR)) {
LLVM_DEBUG(dbgs() << "High cost for expanding trip count scev!\n");
return false;
}
diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 0e8f591d4808..347289e6f201 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -1361,7 +1361,8 @@ int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
hasHardUserWithinLoop(L, Inst))
continue;
- bool HighCost = Rewriter.isHighCostExpansion(ExitValue, L, TTI, Inst);
+ bool HighCost = Rewriter.isHighCostExpansion(
+ ExitValue, L, SCEVCheapExpansionBudget, TTI, Inst);
Value *ExitVal = Rewriter.expandCodeFor(ExitValue, PN->getType(), Inst);
LLVM_DEBUG(dbgs() << "rewriteLoopExitValues: AfterLoopVal = "
diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index 7bee8df0ce18..cc270018156b 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -669,7 +669,7 @@ bool SimplifyIndvar::replaceIVUserWithLoopInvariant(Instruction *I) {
return false;
// Do not generate something ridiculous even if S is loop invariant.
- if (Rewriter.isHighCostExpansion(S, L, TTI, I))
+ if (Rewriter.isHighCostExpansion(S, L, SCEVCheapExpansionBudget, TTI, I))
return false;
auto *IP = GetLoopInvariantInsertPosition(L, I);
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