[llvm] r249685 - Make demanded bits lazy
James Molloy via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 8 05:39:50 PDT 2015
Author: jamesm
Date: Thu Oct 8 07:39:50 2015
New Revision: 249685
URL: http://llvm.org/viewvc/llvm-project?rev=249685&view=rev
Log:
Make demanded bits lazy
The algorithm itself is still eager, but it doesn't get run until a
query function is called. This greatly reduces the compile-time impact
of requiring DemandedBits when at runtime it is not often used.
NFCI.
Modified:
llvm/trunk/include/llvm/Analysis/DemandedBits.h
llvm/trunk/lib/Analysis/DemandedBits.cpp
Modified: llvm/trunk/include/llvm/Analysis/DemandedBits.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/DemandedBits.h?rev=249685&r1=249684&r2=249685&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/DemandedBits.h (original)
+++ llvm/trunk/include/llvm/Analysis/DemandedBits.h Thu Oct 8 07:39:50 2015
@@ -49,6 +49,7 @@ struct DemandedBits : public FunctionPas
bool isInstructionDead(Instruction *I);
private:
+ void performAnalysis();
void determineLiveOperandBits(const Instruction *UserI,
const Instruction *I, unsigned OperandNo,
const APInt &AOut, APInt &AB,
@@ -57,6 +58,8 @@ private:
AssumptionCache *AC;
DominatorTree *DT;
+ Function *F;
+ bool Analyzed;
// The set of visited instructions (non-integer-typed only).
SmallPtrSet<Instruction*, 128> Visited;
Modified: llvm/trunk/lib/Analysis/DemandedBits.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/DemandedBits.cpp?rev=249685&r1=249684&r2=249685&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/DemandedBits.cpp (original)
+++ llvm/trunk/lib/Analysis/DemandedBits.cpp Thu Oct 8 07:39:50 2015
@@ -51,7 +51,7 @@ INITIALIZE_PASS_DEPENDENCY(DominatorTree
INITIALIZE_PASS_END(DemandedBits, "demanded-bits", "Demanded bits analysis",
false, false)
-DemandedBits::DemandedBits() : FunctionPass(ID) {
+DemandedBits::DemandedBits() : FunctionPass(ID), F(nullptr), Analyzed(false) {
initializeDemandedBitsPass(*PassRegistry::getPassRegistry());
}
@@ -243,17 +243,27 @@ void DemandedBits::determineLiveOperandB
}
}
-bool DemandedBits::runOnFunction(Function& F) {
- AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
- DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+bool DemandedBits::runOnFunction(Function& Fn) {
+ F = &Fn;
+ Analyzed = false;
+ return false;
+}
+void DemandedBits::performAnalysis() {
+ if (Analyzed)
+ // Analysis already completed for this function.
+ return;
+ Analyzed = true;
+ AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(*F);
+ DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+
Visited.clear();
AliveBits.clear();
SmallVector<Instruction*, 128> Worklist;
// Collect the set of "root" instructions that are known live.
- for (Instruction &I : instructions(F)) {
+ for (Instruction &I : instructions(*F)) {
if (!isAlwaysLive(&I))
continue;
@@ -340,11 +350,11 @@ bool DemandedBits::runOnFunction(Functio
}
}
}
-
- return false;
}
APInt DemandedBits::getDemandedBits(Instruction *I) {
+ performAnalysis();
+
const DataLayout &DL = I->getParent()->getModule()->getDataLayout();
if (AliveBits.count(I))
return AliveBits[I];
@@ -352,6 +362,8 @@ APInt DemandedBits::getDemandedBits(Inst
}
bool DemandedBits::isInstructionDead(Instruction *I) {
+ performAnalysis();
+
return !Visited.count(I) && AliveBits.find(I) == AliveBits.end() &&
!isAlwaysLive(I);
}
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