[llvm] r219816 - [SLPVectorize] Basic ephemeral-value awareness
Hal Finkel
hfinkel at anl.gov
Wed Oct 15 10:35:01 PDT 2014
Author: hfinkel
Date: Wed Oct 15 12:35:01 2014
New Revision: 219816
URL: http://llvm.org/viewvc/llvm-project?rev=219816&view=rev
Log:
[SLPVectorize] Basic ephemeral-value awareness
The SLP vectorizer should not vectorize ephemeral values. These are used to
express information to the optimizer, and vectorizing them does not lead to
faster code (because the ephemeral values are dropped prior to code generation,
vectorized or not), and obscures the information the instructions are
attempting to communicate (the logic that interprets the arguments to
@llvm.assume generically does not understand vectorized conditions).
Also, uses by ephemeral values are free (because they, and the necessary
extractelement instructions, will be dropped prior to code generation).
Modified:
llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp
llvm/trunk/test/Transforms/SLPVectorizer/X86/insert-element-build-vector.ll
Modified: llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp?rev=219816&r1=219815&r2=219816&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp Wed Oct 15 12:35:01 2014
@@ -21,6 +21,8 @@
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/AssumptionTracker.h"
+#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
@@ -396,10 +398,12 @@ public:
BoUpSLP(Function *Func, ScalarEvolution *Se, const DataLayout *Dl,
TargetTransformInfo *Tti, TargetLibraryInfo *TLi, AliasAnalysis *Aa,
- LoopInfo *Li, DominatorTree *Dt)
+ LoopInfo *Li, DominatorTree *Dt, AssumptionTracker *AT)
: NumLoadsWantToKeepOrder(0), NumLoadsWantToChangeOrder(0),
F(Func), SE(Se), DL(Dl), TTI(Tti), TLI(TLi), AA(Aa), LI(Li), DT(Dt),
- Builder(Se->getContext()) {}
+ Builder(Se->getContext()) {
+ CodeMetrics::collectEphemeralValues(F, AT, EphValues);
+ }
/// \brief Vectorize the tree that starts with the elements in \p VL.
/// Returns the vectorized root.
@@ -555,6 +559,9 @@ private:
/// This list holds pairs of (Internal Scalar : External User).
UserList ExternalUses;
+ /// Values used only by @llvm.assume calls.
+ SmallPtrSet<const Value *, 32> EphValues;
+
/// Holds all of the instructions that we gathered.
SetVector<Instruction *> GatherSeq;
/// A list of blocks that we are going to CSE.
@@ -988,6 +995,16 @@ void BoUpSLP::buildTree_rec(ArrayRef<Val
// We now know that this is a vector of instructions of the same type from
// the same block.
+ // Don't vectorize ephemeral values.
+ for (unsigned i = 0, e = VL.size(); i != e; ++i) {
+ if (EphValues.count(VL[i])) {
+ DEBUG(dbgs() << "SLP: The instruction (" << *VL[i] <<
+ ") is ephemeral.\n");
+ newTreeEntry(VL, false);
+ return;
+ }
+ }
+
// Check if this is a duplicate of another entry.
if (ScalarToTreeEntry.count(VL[0])) {
int Idx = ScalarToTreeEntry[VL[0]];
@@ -1710,6 +1727,12 @@ int BoUpSLP::getTreeCost() {
if (!ExtractCostCalculated.insert(I->Scalar))
continue;
+ // Uses by ephemeral values are free (because the ephemeral value will be
+ // removed prior to code generation, and so the extraction will be
+ // removed as well).
+ if (EphValues.count(I->User))
+ continue;
+
VectorType *VecTy = VectorType::get(I->Scalar->getType(), BundleWidth);
ExtractCost += TTI->getVectorInstrCost(Instruction::ExtractElement, VecTy,
I->Lane);
@@ -2810,6 +2833,7 @@ struct SLPVectorizer : public FunctionPa
AliasAnalysis *AA;
LoopInfo *LI;
DominatorTree *DT;
+ AssumptionTracker *AT;
bool runOnFunction(Function &F) override {
if (skipOptnoneFunction(F))
@@ -2823,6 +2847,7 @@ struct SLPVectorizer : public FunctionPa
AA = &getAnalysis<AliasAnalysis>();
LI = &getAnalysis<LoopInfo>();
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ AT = &getAnalysis<AssumptionTracker>();
StoreRefs.clear();
bool Changed = false;
@@ -2845,7 +2870,7 @@ struct SLPVectorizer : public FunctionPa
// Use the bottom up slp vectorizer to construct chains that start with
// store instructions.
- BoUpSLP R(&F, SE, DL, TTI, TLI, AA, LI, DT);
+ BoUpSLP R(&F, SE, DL, TTI, TLI, AA, LI, DT, AT);
// Scan the blocks in the function in post order.
for (po_iterator<BasicBlock*> it = po_begin(&F.getEntryBlock()),
@@ -2872,6 +2897,7 @@ struct SLPVectorizer : public FunctionPa
void getAnalysisUsage(AnalysisUsage &AU) const override {
FunctionPass::getAnalysisUsage(AU);
+ AU.addRequired<AssumptionTracker>();
AU.addRequired<ScalarEvolution>();
AU.addRequired<AliasAnalysis>();
AU.addRequired<TargetTransformInfo>();
@@ -3746,6 +3772,7 @@ static const char lv_name[] = "SLP Vecto
INITIALIZE_PASS_BEGIN(SLPVectorizer, SV_NAME, lv_name, false, false)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_AG_DEPENDENCY(TargetTransformInfo)
+INITIALIZE_PASS_DEPENDENCY(AssumptionTracker)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
INITIALIZE_PASS_END(SLPVectorizer, SV_NAME, lv_name, false, false)
Modified: llvm/trunk/test/Transforms/SLPVectorizer/X86/insert-element-build-vector.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SLPVectorizer/X86/insert-element-build-vector.ll?rev=219816&r1=219815&r2=219816&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SLPVectorizer/X86/insert-element-build-vector.ll (original)
+++ llvm/trunk/test/Transforms/SLPVectorizer/X86/insert-element-build-vector.ll Wed Oct 15 12:35:01 2014
@@ -35,6 +35,49 @@ define <4 x float> @simple_select(<4 x f
ret <4 x float> %rd
}
+declare void @llvm.assume(i1) nounwind
+
+; This entire tree is ephemeral, don't vectorize any of it.
+define <4 x float> @simple_select_eph(<4 x float> %a, <4 x float> %b, <4 x i32> %c) #0 {
+; CHECK-LABEL: @simple_select_eph(
+; CHECK-NOT: icmp ne <4 x i32>
+; CHECK-NOT: select <4 x i1>
+ %c0 = extractelement <4 x i32> %c, i32 0
+ %c1 = extractelement <4 x i32> %c, i32 1
+ %c2 = extractelement <4 x i32> %c, i32 2
+ %c3 = extractelement <4 x i32> %c, i32 3
+ %a0 = extractelement <4 x float> %a, i32 0
+ %a1 = extractelement <4 x float> %a, i32 1
+ %a2 = extractelement <4 x float> %a, i32 2
+ %a3 = extractelement <4 x float> %a, i32 3
+ %b0 = extractelement <4 x float> %b, i32 0
+ %b1 = extractelement <4 x float> %b, i32 1
+ %b2 = extractelement <4 x float> %b, i32 2
+ %b3 = extractelement <4 x float> %b, i32 3
+ %cmp0 = icmp ne i32 %c0, 0
+ %cmp1 = icmp ne i32 %c1, 0
+ %cmp2 = icmp ne i32 %c2, 0
+ %cmp3 = icmp ne i32 %c3, 0
+ %s0 = select i1 %cmp0, float %a0, float %b0
+ %s1 = select i1 %cmp1, float %a1, float %b1
+ %s2 = select i1 %cmp2, float %a2, float %b2
+ %s3 = select i1 %cmp3, float %a3, float %b3
+ %ra = insertelement <4 x float> undef, float %s0, i32 0
+ %rb = insertelement <4 x float> %ra, float %s1, i32 1
+ %rc = insertelement <4 x float> %rb, float %s2, i32 2
+ %rd = insertelement <4 x float> %rc, float %s3, i32 3
+ %q0 = extractelement <4 x float> %rd, i32 0
+ %q1 = extractelement <4 x float> %rd, i32 1
+ %q2 = extractelement <4 x float> %rd, i32 2
+ %q3 = extractelement <4 x float> %rd, i32 3
+ %q4 = fadd float %q0, %q1
+ %q5 = fadd float %q2, %q3
+ %q6 = fadd float %q4, %q5
+ %qi = fcmp olt float %q6, %q5
+ call void @llvm.assume(i1 %qi)
+ ret <4 x float> undef
+}
+
; Insert in an order different from the vector indices to make sure it
; doesn't matter
define <4 x float> @simple_select_insert_out_of_order(<4 x float> %a, <4 x float> %b, <4 x i32> %c) #0 {
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