[llvm] r278378 - Target independent codesize heuristics for Loop Idiom Recognition
Andrew Kaylor via llvm-commits
llvm-commits at lists.llvm.org
Thu Aug 11 11:28:33 PDT 2016
Author: akaylor
Date: Thu Aug 11 13:28:33 2016
New Revision: 278378
URL: http://llvm.org/viewvc/llvm-project?rev=278378&view=rev
Log:
Target independent codesize heuristics for Loop Idiom Recognition
Patch by Sunita Marathe
Differential Revision: https://reviews.llvm.org/D21449
Added:
llvm/trunk/test/Transforms/LoopIdiom/lir-heurs-multi-block-loop.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp?rev=278378&r1=278377&r2=278378&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp Thu Aug 11 13:28:33 2016
@@ -11,6 +11,12 @@
// non-loop form. In cases that this kicks in, it can be a significant
// performance win.
//
+// If compiling for code size we avoid idiom recognition if the resulting
+// code could be larger than the code for the original loop. One way this could
+// happen is if the loop is not removable after idiom recognition due to the
+// presence of non-idiom instructions. The initial implementation of the
+// heuristics applies to idioms in multi-block loops.
+//
//===----------------------------------------------------------------------===//
//
// TODO List:
@@ -65,6 +71,12 @@ using namespace llvm;
STATISTIC(NumMemSet, "Number of memset's formed from loop stores");
STATISTIC(NumMemCpy, "Number of memcpy's formed from loop load+stores");
+static cl::opt<bool> UseLIRCodeSizeHeurs(
+ "use-lir-code-size-heurs",
+ cl::desc("Use loop idiom recognition code size heuristics when compiling"
+ "with -Os/-Oz"),
+ cl::init(true), cl::Hidden);
+
namespace {
class LoopIdiomRecognize {
@@ -76,6 +88,7 @@ class LoopIdiomRecognize {
TargetLibraryInfo *TLI;
const TargetTransformInfo *TTI;
const DataLayout *DL;
+ bool ApplyCodeSizeHeuristics;
public:
explicit LoopIdiomRecognize(AliasAnalysis *AA, DominatorTree *DT,
@@ -117,8 +130,10 @@ private:
Instruction *TheStore,
SmallPtrSetImpl<Instruction *> &Stores,
const SCEVAddRecExpr *Ev, const SCEV *BECount,
- bool NegStride);
+ bool NegStride, bool IsLoopMemset = false);
bool processLoopStoreOfLoopLoad(StoreInst *SI, const SCEV *BECount);
+ bool avoidLIRForMultiBlockLoop(bool IsMemset = false,
+ bool IsLoopMemset = false);
/// @}
/// \name Noncountable Loop Idiom Handling
@@ -229,6 +244,10 @@ bool LoopIdiomRecognize::runOnLoop(Loop
if (Name == "memset" || Name == "memcpy")
return false;
+ // Determine if code size heuristics need to be applied.
+ ApplyCodeSizeHeuristics =
+ L->getHeader()->getParent()->optForSize() && UseLIRCodeSizeHeurs;
+
HasMemset = TLI->has(LibFunc::memset);
HasMemsetPattern = TLI->has(LibFunc::memset_pattern16);
HasMemcpy = TLI->has(LibFunc::memcpy);
@@ -689,7 +708,7 @@ bool LoopIdiomRecognize::processLoopMemS
bool NegStride = SizeInBytes == -Stride;
return processLoopStridedStore(Pointer, (unsigned)SizeInBytes,
MSI->getAlignment(), SplatValue, MSI, MSIs, Ev,
- BECount, NegStride);
+ BECount, NegStride, /*IsLoopMemset=*/true);
}
/// mayLoopAccessLocation - Return true if the specified loop might access the
@@ -745,7 +764,7 @@ bool LoopIdiomRecognize::processLoopStri
Value *DestPtr, unsigned StoreSize, unsigned StoreAlignment,
Value *StoredVal, Instruction *TheStore,
SmallPtrSetImpl<Instruction *> &Stores, const SCEVAddRecExpr *Ev,
- const SCEV *BECount, bool NegStride) {
+ const SCEV *BECount, bool NegStride, bool IsLoopMemset) {
Value *SplatValue = isBytewiseValue(StoredVal);
Constant *PatternValue = nullptr;
@@ -786,6 +805,9 @@ bool LoopIdiomRecognize::processLoopStri
return false;
}
+ if (avoidLIRForMultiBlockLoop(/*IsMemset=*/true, IsLoopMemset))
+ return false;
+
// Okay, everything looks good, insert the memset.
// The # stored bytes is (BECount+1)*Size. Expand the trip count out to
@@ -917,6 +939,9 @@ bool LoopIdiomRecognize::processLoopStor
return false;
}
+ if (avoidLIRForMultiBlockLoop())
+ return false;
+
// Okay, everything is safe, we can transform this!
// The # stored bytes is (BECount+1)*Size. Expand the trip count out to
@@ -948,6 +973,23 @@ bool LoopIdiomRecognize::processLoopStor
return true;
}
+// When compiling for codesize we avoid idiom recognition for a multi-block loop
+// unless it is a loop_memset idiom or a memset/memcpy idiom in a nested loop.
+//
+bool LoopIdiomRecognize::avoidLIRForMultiBlockLoop(bool IsMemset,
+ bool IsLoopMemset) {
+ if (ApplyCodeSizeHeuristics && CurLoop->getNumBlocks() > 1) {
+ if (!CurLoop->getParentLoop() && (!IsMemset || !IsLoopMemset)) {
+ DEBUG(dbgs() << " " << CurLoop->getHeader()->getParent()->getName()
+ << " : LIR " << (IsMemset ? "Memset" : "Memcpy")
+ << " avoided: multi-block top-level loop\n");
+ return true;
+ }
+ }
+
+ return false;
+}
+
bool LoopIdiomRecognize::runOnNoncountableLoop() {
return recognizePopcount();
}
Added: llvm/trunk/test/Transforms/LoopIdiom/lir-heurs-multi-block-loop.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopIdiom/lir-heurs-multi-block-loop.ll?rev=278378&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopIdiom/lir-heurs-multi-block-loop.ll (added)
+++ llvm/trunk/test/Transforms/LoopIdiom/lir-heurs-multi-block-loop.ll Thu Aug 11 13:28:33 2016
@@ -0,0 +1,182 @@
+; RUN: opt -basicaa -loop-idiom -use-lir-code-size-heurs=true < %s -S | FileCheck %s
+
+; When compiling for codesize we avoid idiom recognition for a
+; multi-block loop unless it is one of
+; - a loop_memset idiom, or
+; - a memset/memcpy idiom in a nested loop.
+
+declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1)
+ at APPLES = common global i32 0, align 4
+ at ORANGES = common global i32 0, align 4
+
+; LIR allowed: loop_memset idiom in multi-block loop.
+; ===================================================
+; CHECK-LABEL: @LoopMemset
+; CHECK: for.body.preheader:
+; CHECK: call void @llvm.memset
+; CHECK: for.body:
+;
+define i32 @LoopMemset([2048 x i8]* noalias nocapture %DST, i32 %SIZE) local_unnamed_addr optsize {
+entry:
+ %cmp12 = icmp sgt i32 %SIZE, 0
+ br i1 %cmp12, label %for.body.preheader, label %for.end
+
+for.body.preheader: ; preds = %entry
+ br label %for.body
+
+for.body: ; preds = %for.body.preheader, %for.inc
+ %indvars.iv = phi i64 [ 0, %for.body.preheader ], [ %indvars.iv.next, %for.inc ]
+ %BASKET.013 = phi i32 [ %BASKET.1, %for.inc ], [ 0, %for.body.preheader ]
+ %arraydecay = getelementptr inbounds [2048 x i8], [2048 x i8]* %DST, i64 %indvars.iv, i64 0
+ tail call void @llvm.memset.p0i8.i64(i8* %arraydecay, i8 -1, i64 2048, i32 1, i1 false)
+ %0 = trunc i64 %indvars.iv to i32
+ %rem11 = and i32 %0, 1
+ %cmp1 = icmp eq i32 %rem11, 0
+ %1 = load i32, i32* @ORANGES, align 4
+ %2 = load i32, i32* @APPLES, align 4
+ br i1 %cmp1, label %if.then, label %if.else
+
+if.else: ; preds = %for.body
+ %dec3 = add nsw i32 %2, -1
+ store i32 %dec3, i32* @APPLES, align 4
+ br label %for.inc
+
+if.then: ; preds = %for.body
+ %dec = add nsw i32 %1, -1
+ store i32 %dec, i32* @ORANGES, align 4
+ br label %for.inc
+
+for.inc: ; preds = %if.then, %if.else
+ %.pn = phi i32 [ %2, %if.then ], [ %1, %if.else ]
+ %BASKET.1 = add nsw i32 %.pn, %BASKET.013
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+ %exitcond = icmp ne i32 %lftr.wideiv, %SIZE
+ br i1 %exitcond, label %for.body, label %for.end.loopexit
+
+for.end.loopexit: ; preds = %for.inc
+ %BASKET.1.lcssa = phi i32 [ %BASKET.1, %for.inc ]
+ br label %for.end
+
+for.end: ; preds = %for.end.loopexit, %entry
+ %BASKET.0.lcssa = phi i32 [ 0, %entry ], [ %BASKET.1.lcssa, %for.end.loopexit ]
+ ret i32 %BASKET.0.lcssa
+}
+
+; LIR allowed: memset idiom in multi-block nested loop,
+; which is recognized as a loop_memset in its turn.
+; =====================================================
+; CHECK-LABEL: @NestedMemset_LoopMemset
+; CHECK: for.cond1.preheader.preheader:
+; CHECK: call void @llvm.memset
+; CHECK: for.cond1.preheader:
+;
+define i32 @NestedMemset_LoopMemset([2046 x i8]* noalias nocapture %DST, i32 %SIZE) local_unnamed_addr optsize {
+entry:
+ %cmp25 = icmp sgt i32 %SIZE, 0
+ br i1 %cmp25, label %for.cond1.preheader.preheader, label %for.end11
+
+for.cond1.preheader.preheader: ; preds = %entry
+ br label %for.cond1.preheader
+
+for.cond1.preheader: ; preds = %for.cond1.preheader.preheader, %for.inc9
+ %i.027 = phi i32 [ %inc10, %for.inc9 ], [ 0, %for.cond1.preheader.preheader ]
+ %BASKET.026 = phi i32 [ %BASKET.2.lcssa, %for.inc9 ], [ 0, %for.cond1.preheader.preheader ]
+ %idxprom4 = sext i32 %i.027 to i64
+ %rem22 = and i32 %i.027, 1
+ %cmp6 = icmp eq i32 %rem22, 0
+ br label %for.body3
+
+for.body3: ; preds = %for.cond1.preheader, %for.inc
+ %indvars.iv = phi i64 [ 0, %for.cond1.preheader ], [ %indvars.iv.next, %for.inc ]
+ %BASKET.123 = phi i32 [ %BASKET.026, %for.cond1.preheader ], [ %BASKET.2, %for.inc ]
+ %arrayidx5 = getelementptr inbounds [2046 x i8], [2046 x i8]* %DST, i64 %idxprom4, i64 %indvars.iv
+ store i8 -1, i8* %arrayidx5, align 1
+ %0 = load i32, i32* @APPLES, align 4
+ %1 = load i32, i32* @ORANGES, align 4
+ br i1 %cmp6, label %if.then, label %if.else
+
+if.else: ; preds = %for.body3
+ %dec8 = add nsw i32 %0, -1
+ store i32 %dec8, i32* @APPLES, align 4
+ br label %for.inc
+
+if.then: ; preds = %for.body3
+ %dec = add nsw i32 %1, -1
+ store i32 %dec, i32* @ORANGES, align 4
+ br label %for.inc
+
+for.inc: ; preds = %if.then, %if.else
+ %.pn = phi i32 [ %0, %if.then ], [ %1, %if.else ]
+ %BASKET.2 = add nsw i32 %.pn, %BASKET.123
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %exitcond = icmp ne i64 %indvars.iv.next, 2046
+ br i1 %exitcond, label %for.body3, label %for.inc9
+
+for.inc9: ; preds = %for.inc
+ %BASKET.2.lcssa = phi i32 [ %BASKET.2, %for.inc ]
+ %inc10 = add nsw i32 %i.027, 1
+ %cmp = icmp slt i32 %inc10, %SIZE
+ br i1 %cmp, label %for.cond1.preheader, label %for.end11.loopexit
+
+for.end11.loopexit: ; preds = %for.inc9
+ %BASKET.2.lcssa.lcssa = phi i32 [ %BASKET.2.lcssa, %for.inc9 ]
+ br label %for.end11
+
+for.end11: ; preds = %for.end11.loopexit, %entry
+ %BASKET.0.lcssa = phi i32 [ 0, %entry ], [ %BASKET.2.lcssa.lcssa, %for.end11.loopexit ]
+ ret i32 %BASKET.0.lcssa
+}
+
+; LIR avoided: memset idiom in multi-block top-level loop.
+; ========================================================
+; CHECK-LABEL: @Non_NestedMemset
+; CHECK-NOT: call void @llvm.memset
+;
+define i32 @Non_NestedMemset(i8* noalias nocapture %DST, i32 %SIZE) local_unnamed_addr optsize {
+entry:
+ %cmp12 = icmp sgt i32 %SIZE, 0
+ br i1 %cmp12, label %for.body.preheader, label %for.end
+
+for.body.preheader: ; preds = %entry
+ br label %for.body
+
+for.body: ; preds = %for.body.preheader, %for.inc
+ %indvars.iv = phi i64 [ 0, %for.body.preheader ], [ %indvars.iv.next, %for.inc ]
+ %BASKET.013 = phi i32 [ %BASKET.1, %for.inc ], [ 0, %for.body.preheader ]
+ %arrayidx = getelementptr inbounds i8, i8* %DST, i64 %indvars.iv
+ store i8 -1, i8* %arrayidx, align 1
+ %0 = trunc i64 %indvars.iv to i32
+ %rem11 = and i32 %0, 1
+ %cmp1 = icmp eq i32 %rem11, 0
+ %1 = load i32, i32* @ORANGES, align 4
+ %2 = load i32, i32* @APPLES, align 4
+ br i1 %cmp1, label %if.then, label %if.else
+
+if.else: ; preds = %for.body
+ %dec3 = add nsw i32 %2, -1
+ store i32 %dec3, i32* @APPLES, align 4
+ br label %for.inc
+
+if.then: ; preds = %for.body
+ %dec = add nsw i32 %1, -1
+ store i32 %dec, i32* @ORANGES, align 4
+ br label %for.inc
+
+for.inc: ; preds = %if.then, %if.else
+ %.pn = phi i32 [ %2, %if.then ], [ %1, %if.else ]
+ %BASKET.1 = add nsw i32 %.pn, %BASKET.013
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+ %exitcond = icmp ne i32 %lftr.wideiv, %SIZE
+ br i1 %exitcond, label %for.body, label %for.end.loopexit
+
+for.end.loopexit: ; preds = %for.inc
+ %BASKET.1.lcssa = phi i32 [ %BASKET.1, %for.inc ]
+ br label %for.end
+
+for.end: ; preds = %for.end.loopexit, %entry
+ %BASKET.0.lcssa = phi i32 [ 0, %entry ], [ %BASKET.1.lcssa, %for.end.loopexit ]
+ ret i32 %BASKET.0.lcssa
+}
+
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