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LoopVectorizer: Calculate the number of pointers to disambiguate at runtime based on the numbers of reads and writes.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180593 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nadav Rotem 2013-04-26 05:08:59 +00:00
parent 276b8549ee
commit 7557e521e5
2 changed files with 95 additions and 4 deletions
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15
lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -114,9 +114,9 @@ TinyTripCountVectorThreshold("vectorizer-min-trip-count", cl::init(16),
/// 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::canVectorizeMemory() {
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::canVectorizeMemory() {
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::canVectorizeMemory() {
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::canVectorizeMemory() {
// 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;
}

84
test/Transforms/LoopVectorize/runtime-limit.ll Normal file
View File

@ -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
}