[llvm] r214599 - Add diagnostics to the vectorizer cost model.
Tyler Nowicki
tnowicki at apple.com
Fri Aug 1 17:14:03 PDT 2014
Author: tnowicki
Date: Fri Aug 1 19:14:03 2014
New Revision: 214599
URL: http://llvm.org/viewvc/llvm-project?rev=214599&view=rev
Log:
Add diagnostics to the vectorizer cost model.
When the cost model determines vectorization is not possible/profitable these remarks print an analysis of that decision.
Note that in selectVectorizationFactor() we can assume that OptForSize and ForceVectorization are mutually exclusive.
Reviewed by Arnold Schwaighofer
Added:
llvm/trunk/test/Transforms/LoopVectorize/conditional-assignment.ll
Modified:
llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
Modified: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp?rev=214599&r1=214598&r2=214599&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Fri Aug 1 19:14:03 2014
@@ -209,6 +209,7 @@ namespace {
// Forward declarations.
class LoopVectorizationLegality;
class LoopVectorizationCostModel;
+class LoopVectorizeHints;
/// Optimization analysis message produced during vectorization. Messages inform
/// the user why vectorization did not occur.
@@ -877,8 +878,9 @@ public:
LoopVectorizationCostModel(Loop *L, ScalarEvolution *SE, LoopInfo *LI,
LoopVectorizationLegality *Legal,
const TargetTransformInfo &TTI,
- const DataLayout *DL, const TargetLibraryInfo *TLI)
- : TheLoop(L), SE(SE), LI(LI), Legal(Legal), TTI(TTI), DL(DL), TLI(TLI) {}
+ const DataLayout *DL, const TargetLibraryInfo *TLI,
+ const Function *F, const LoopVectorizeHints *Hints)
+ : TheLoop(L), SE(SE), LI(LI), Legal(Legal), TTI(TTI), DL(DL), TLI(TLI), TheFunction(F), Hints(Hints) {}
/// Information about vectorization costs
struct VectorizationFactor {
@@ -889,9 +891,7 @@ public:
/// This method checks every power of two up to VF. If UserVF is not ZERO
/// then this vectorization factor will be selected if vectorization is
/// possible.
- VectorizationFactor selectVectorizationFactor(bool OptForSize,
- unsigned UserVF,
- bool ForceVectorization);
+ VectorizationFactor selectVectorizationFactor(bool OptForSize);
/// \return The size (in bits) of the widest type in the code that
/// needs to be vectorized. We ignore values that remain scalar such as
@@ -903,8 +903,7 @@ public:
/// based on register pressure and other parameters.
/// VF and LoopCost are the selected vectorization factor and the cost of the
/// selected VF.
- unsigned selectUnrollFactor(bool OptForSize, unsigned UserUF, unsigned VF,
- unsigned LoopCost);
+ unsigned selectUnrollFactor(bool OptForSize, unsigned VF, unsigned LoopCost);
/// \brief A struct that represents some properties of the register usage
/// of a loop.
@@ -940,6 +939,16 @@ private:
/// as a vector operation.
bool isConsecutiveLoadOrStore(Instruction *I);
+ /// Report an analysis message to assist the user in diagnosing loops that are
+ /// not vectorized.
+ void emitAnalysis(Report &Message) {
+ DebugLoc DL = TheLoop->getStartLoc();
+ if (Instruction *I = Message.getInstr())
+ DL = I->getDebugLoc();
+ emitOptimizationRemarkAnalysis(TheFunction->getContext(), DEBUG_TYPE,
+ *TheFunction, DL, Message.str());
+ }
+
/// The loop that we evaluate.
Loop *TheLoop;
/// Scev analysis.
@@ -954,6 +963,9 @@ private:
const DataLayout *DL;
/// Target Library Info.
const TargetLibraryInfo *TLI;
+ const Function *TheFunction;
+ // Loop Vectorize Hint.
+ const LoopVectorizeHints *Hints;
};
/// Utility class for getting and setting loop vectorizer hints in the form
@@ -1301,7 +1313,7 @@ struct LoopVectorize : public FunctionPa
}
// Use the cost model.
- LoopVectorizationCostModel CM(L, SE, LI, &LVL, *TTI, DL, TLI);
+ LoopVectorizationCostModel CM(L, SE, LI, &LVL, *TTI, DL, TLI, F, &Hints);
// Check the function attributes to find out if this function should be
// optimized for size.
@@ -1336,13 +1348,11 @@ struct LoopVectorize : public FunctionPa
// Select the optimal vectorization factor.
const LoopVectorizationCostModel::VectorizationFactor VF =
- CM.selectVectorizationFactor(OptForSize, Hints.getWidth(),
- Hints.getForce() ==
- LoopVectorizeHints::FK_Enabled);
+ CM.selectVectorizationFactor(OptForSize);
// Select the unroll factor.
const unsigned UF =
- CM.selectUnrollFactor(OptForSize, Hints.getUnroll(), VF.Width, VF.Cost);
+ CM.selectUnrollFactor(OptForSize, VF.Width, VF.Cost);
DEBUG(dbgs() << "LV: Found a vectorizable loop (" << VF.Width << ") in "
<< DebugLocStr << '\n');
@@ -5263,17 +5273,17 @@ bool LoopVectorizationLegality::blockCan
}
LoopVectorizationCostModel::VectorizationFactor
-LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize,
- unsigned UserVF,
- bool ForceVectorization) {
+LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize) {
// Width 1 means no vectorize
VectorizationFactor Factor = { 1U, 0U };
if (OptForSize && Legal->getRuntimePointerCheck()->Need) {
+ emitAnalysis(Report() << "runtime pointer checks needed. Enable vectorization of this loop with '#pragma clang loop vectorize(enable)' when compiling with -Os");
DEBUG(dbgs() << "LV: Aborting. Runtime ptr check is required in Os.\n");
return Factor;
}
if (!EnableCondStoresVectorization && Legal->NumPredStores) {
+ emitAnalysis(Report() << "store that is conditionally executed prevents vectorization");
DEBUG(dbgs() << "LV: No vectorization. There are conditional stores.\n");
return Factor;
}
@@ -5308,6 +5318,7 @@ LoopVectorizationCostModel::selectVector
if (OptForSize) {
// If we are unable to calculate the trip count then don't try to vectorize.
if (TC < 2) {
+ emitAnalysis(Report() << "unable to calculate the loop count due to complex control flow");
DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
return Factor;
}
@@ -5321,11 +5332,13 @@ LoopVectorizationCostModel::selectVector
// If the trip count that we found modulo the vectorization factor is not
// zero then we require a tail.
if (VF < 2) {
+ emitAnalysis(Report() << "cannot optimize for size and vectorize at the same time. Enable vectorization of this loop with '#pragma clang loop vectorize(enable)' when compiling with -Os");
DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
return Factor;
}
}
+ int UserVF = Hints->getWidth();
if (UserVF != 0) {
assert(isPowerOf2_32(UserVF) && "VF needs to be a power of two");
DEBUG(dbgs() << "LV: Using user VF " << UserVF << ".\n");
@@ -5341,6 +5354,7 @@ LoopVectorizationCostModel::selectVector
unsigned Width = 1;
DEBUG(dbgs() << "LV: Scalar loop costs: " << (int)ScalarCost << ".\n");
+ bool ForceVectorization = Hints->getForce() == LoopVectorizeHints::FK_Enabled;
// Ignore scalar width, because the user explicitly wants vectorization.
if (ForceVectorization && VF > 1) {
Width = 2;
@@ -5410,7 +5424,6 @@ unsigned LoopVectorizationCostModel::get
unsigned
LoopVectorizationCostModel::selectUnrollFactor(bool OptForSize,
- unsigned UserUF,
unsigned VF,
unsigned LoopCost) {
@@ -5429,6 +5442,7 @@ LoopVectorizationCostModel::selectUnroll
// to the increased register pressure.
// Use the user preference, unless 'auto' is selected.
+ int UserUF = Hints->getUnroll();
if (UserUF != 0)
return UserUF;
Added: llvm/trunk/test/Transforms/LoopVectorize/conditional-assignment.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/conditional-assignment.ll?rev=214599&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/conditional-assignment.ll (added)
+++ llvm/trunk/test/Transforms/LoopVectorize/conditional-assignment.ll Fri Aug 1 19:14:03 2014
@@ -0,0 +1,58 @@
+; RUN: opt < %s -loop-vectorize -S -pass-remarks-missed='loop-vectorize' -pass-remarks-analysis='loop-vectorize' 2>&1 | FileCheck %s
+
+; CHECK: remark: source.c:2:8: loop not vectorized: store that is conditionally executed prevents vectorization
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.9.0"
+
+; Function Attrs: nounwind ssp uwtable
+define void @conditional_store(i32* noalias nocapture %indices) #0 {
+entry:
+ br label %for.body, !dbg !10
+
+for.body: ; preds = %for.inc, %entry
+ %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.inc ]
+ %arrayidx = getelementptr inbounds i32* %indices, i64 %indvars.iv, !dbg !12
+ %0 = load i32* %arrayidx, align 4, !dbg !12, !tbaa !14
+ %cmp1 = icmp eq i32 %0, 1024, !dbg !12
+ br i1 %cmp1, label %if.then, label %for.inc, !dbg !12
+
+if.then: ; preds = %for.body
+ store i32 0, i32* %arrayidx, align 4, !dbg !18, !tbaa !14
+ br label %for.inc, !dbg !18
+
+for.inc: ; preds = %for.body, %if.then
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1, !dbg !10
+ %exitcond = icmp eq i64 %indvars.iv.next, 4096, !dbg !10
+ br i1 %exitcond, label %for.end, label %for.body, !dbg !10
+
+for.end: ; preds = %for.inc
+ ret void, !dbg !19
+}
+
+attributes #0 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7, !8}
+!llvm.ident = !{!9}
+
+!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.6.0", i1 true, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !"", i32 2}
+!1 = metadata !{metadata !"source.c", metadata !"."}
+!2 = metadata !{}
+!3 = metadata !{metadata !4}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"conditional_store", metadata !"conditional_store", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 true, void (i32*)* @conditional_store, null, null, metadata !2, i32 1}
+!5 = metadata !{i32 786473, metadata !1}
+!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !2, i32 0, null, null, null}
+!7 = metadata !{i32 2, metadata !"Dwarf Version", i32 2}
+!8 = metadata !{i32 2, metadata !"Debug Info Version", i32 1}
+!9 = metadata !{metadata !"clang version 3.6.0"}
+!10 = metadata !{i32 2, i32 8, metadata !11, null}
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+!13 = metadata !{i32 786443, metadata !1, metadata !11, i32 3, i32 9, i32 0, i32 1}
+!14 = metadata !{metadata !15, metadata !15, i64 0}
+!15 = metadata !{metadata !"int", metadata !16, i64 0}
+!16 = metadata !{metadata !"omnipotent char", metadata !17, i64 0}
+!17 = metadata !{metadata !"Simple C/C++ TBAA"}
+!18 = metadata !{i32 3, i32 29, metadata !13, null}
+!19 = metadata !{i32 4, i32 1, metadata !4, null}
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