[llvm] r180593 - LoopVectorizer: Calculate the number of pointers to disambiguate at runtime based on the numbers of reads and writes.
Nadav Rotem
nrotem at apple.com
Thu Apr 25 22:08:59 PDT 2013
Author: nadav
Date: Fri Apr 26 00:08:59 2013
New Revision: 180593
URL: http://llvm.org/viewvc/llvm-project?rev=180593&view=rev
Log:
LoopVectorizer: Calculate the number of pointers to disambiguate at runtime based on the numbers of reads and writes.
Added:
llvm/trunk/test/Transforms/LoopVectorize/runtime-limit.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=180593&r1=180592&r2=180593&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Fri Apr 26 00:08:59 2013
@@ -114,9 +114,9 @@ TinyTripCountVectorThreshold("vectorizer
/// We don't unroll loops with a known constant trip count below this number.
static const unsigned TinyTripCountUnrollThreshold = 128;
-/// When performing a runtime memory check, do not check more than this
-/// number of pointers. Notice that the check is quadratic!
-static const unsigned RuntimeMemoryCheckThreshold = 4;
+/// When performing memory disambiguation checks at runtime do not make more
+/// than this number of comparisons.
+static const unsigned RuntimeMemoryCheckThreshold = 8;
/// We use a metadata with this name to indicate that a scalar loop was
/// vectorized and that we don't need to re-vectorize it if we run into it
@@ -2679,6 +2679,9 @@ bool LoopVectorizationLegality::canVecto
return true;
}
+ unsigned NumReadPtrs = 0;
+ unsigned NumWritePtrs = 0;
+
// Find pointers with computable bounds. We are going to use this information
// to place a runtime bound check.
bool CanDoRT = true;
@@ -2687,6 +2690,7 @@ bool LoopVectorizationLegality::canVecto
Value *V = (*MI).first;
if (hasComputableBounds(V)) {
PtrRtCheck.insert(SE, TheLoop, V, true);
+ NumWritePtrs++;
DEBUG(dbgs() << "LV: Found a runtime check ptr:" << *V <<"\n");
} else {
CanDoRT = false;
@@ -2697,6 +2701,7 @@ bool LoopVectorizationLegality::canVecto
Value *V = (*MI).first;
if (hasComputableBounds(V)) {
PtrRtCheck.insert(SE, TheLoop, V, false);
+ NumReadPtrs++;
DEBUG(dbgs() << "LV: Found a runtime check ptr:" << *V <<"\n");
} else {
CanDoRT = false;
@@ -2706,7 +2711,9 @@ bool LoopVectorizationLegality::canVecto
// Check that we did not collect too many pointers or found a
// unsizeable pointer.
- if (!CanDoRT || PtrRtCheck.Pointers.size() > RuntimeMemoryCheckThreshold) {
+ unsigned NumComparisons = (NumWritePtrs * (NumReadPtrs + NumWritePtrs - 1));
+ DEBUG(dbgs() << "LV: We need to compare " << NumComparisons << " ptrs.\n");
+ if (!CanDoRT || NumComparisons > RuntimeMemoryCheckThreshold) {
PtrRtCheck.reset();
CanDoRT = false;
}
Added: llvm/trunk/test/Transforms/LoopVectorize/runtime-limit.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/runtime-limit.ll?rev=180593&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/runtime-limit.ll (added)
+++ llvm/trunk/test/Transforms/LoopVectorize/runtime-limit.ll Fri Apr 26 00:08:59 2013
@@ -0,0 +1,84 @@
+; RUN: opt < %s -loop-vectorize -force-vector-unroll=1 -force-vector-width=4 -dce -instcombine -S | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.8.0"
+
+; We are vectorizing with 6 runtime checks.
+;CHECK: func1x6
+;CHECK: <4 x i32>
+;CHECK: ret
+define i32 @func1x6(i32* nocapture %out, i32* nocapture %A, i32* nocapture %B, i32* nocapture %C, i32* nocapture %D, i32* nocapture %E, i32* nocapture %F) {
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.body, %entry
+ %i.016 = phi i64 [ 0, %entry ], [ %inc, %for.body ]
+ %arrayidx = getelementptr inbounds i32* %A, i64 %i.016
+ %0 = load i32* %arrayidx, align 4
+ %arrayidx1 = getelementptr inbounds i32* %B, i64 %i.016
+ %1 = load i32* %arrayidx1, align 4
+ %add = add nsw i32 %1, %0
+ %arrayidx2 = getelementptr inbounds i32* %C, i64 %i.016
+ %2 = load i32* %arrayidx2, align 4
+ %add3 = add nsw i32 %add, %2
+ %arrayidx4 = getelementptr inbounds i32* %E, i64 %i.016
+ %3 = load i32* %arrayidx4, align 4
+ %add5 = add nsw i32 %add3, %3
+ %arrayidx6 = getelementptr inbounds i32* %F, i64 %i.016
+ %4 = load i32* %arrayidx6, align 4
+ %add7 = add nsw i32 %add5, %4
+ %arrayidx8 = getelementptr inbounds i32* %out, i64 %i.016
+ store i32 %add7, i32* %arrayidx8, align 4
+ %inc = add i64 %i.016, 1
+ %exitcond = icmp eq i64 %inc, 256
+ br i1 %exitcond, label %for.end, label %for.body
+
+for.end: ; preds = %for.body
+ ret i32 undef
+}
+
+; We are not vectorizing with 12 runtime checks.
+;CHECK: func2x6
+;CHECK-NOT: <4 x i32>
+;CHECK: ret
+define i32 @func2x6(i32* nocapture %out, i32* nocapture %out2, i32* nocapture %A, i32* nocapture %B, i32* nocapture %C, i32* nocapture %D, i32* nocapture %E, i32* nocapture %F) {
+entry:
+ br label %for.body
+
+for.body: ; preds = %for.body, %entry
+ %i.037 = phi i64 [ 0, %entry ], [ %inc, %for.body ]
+ %arrayidx = getelementptr inbounds i32* %A, i64 %i.037
+ %0 = load i32* %arrayidx, align 4
+ %arrayidx1 = getelementptr inbounds i32* %B, i64 %i.037
+ %1 = load i32* %arrayidx1, align 4
+ %add = add nsw i32 %1, %0
+ %arrayidx2 = getelementptr inbounds i32* %C, i64 %i.037
+ %2 = load i32* %arrayidx2, align 4
+ %add3 = add nsw i32 %add, %2
+ %arrayidx4 = getelementptr inbounds i32* %E, i64 %i.037
+ %3 = load i32* %arrayidx4, align 4
+ %add5 = add nsw i32 %add3, %3
+ %arrayidx6 = getelementptr inbounds i32* %F, i64 %i.037
+ %4 = load i32* %arrayidx6, align 4
+ %add7 = add nsw i32 %add5, %4
+ %arrayidx8 = getelementptr inbounds i32* %out, i64 %i.037
+ store i32 %add7, i32* %arrayidx8, align 4
+ %5 = load i32* %arrayidx, align 4
+ %6 = load i32* %arrayidx1, align 4
+ %add11 = add nsw i32 %6, %5
+ %7 = load i32* %arrayidx2, align 4
+ %add13 = add nsw i32 %add11, %7
+ %8 = load i32* %arrayidx4, align 4
+ %add15 = add nsw i32 %add13, %8
+ %9 = load i32* %arrayidx6, align 4
+ %add17 = add nsw i32 %add15, %9
+ %arrayidx18 = getelementptr inbounds i32* %out2, i64 %i.037
+ store i32 %add17, i32* %arrayidx18, align 4
+ %inc = add i64 %i.037, 1
+ %exitcond = icmp eq i64 %inc, 256
+ br i1 %exitcond, label %for.end, label %for.body
+
+for.end: ; preds = %for.body
+ ret i32 undef
+}
+
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