[llvm] r278573 - [LoopVectorize] Detect loops in the innermost loop before creating InnerLoopVectorizer
Tim Shen via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 12 15:47:13 PDT 2016
Author: timshen
Date: Fri Aug 12 17:47:13 2016
New Revision: 278573
URL: http://llvm.org/viewvc/llvm-project?rev=278573&view=rev
Log:
[LoopVectorize] Detect loops in the innermost loop before creating InnerLoopVectorizer
InnerLoopVectorizer shouldn't handle a loop with cycles inside the loop
body, even if that cycle isn't a natural loop.
Fixes PR28541.
Differential Revision: https://reviews.llvm.org/D22952
Added:
llvm/trunk/test/Transforms/LoopVectorize/pr28541.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=278573&r1=278572&r2=278573&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Fri Aug 12 17:47:13 2016
@@ -50,6 +50,7 @@
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/SCCIterator.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
@@ -220,6 +221,81 @@ class LoopVectorizationLegality;
class LoopVectorizationCostModel;
class LoopVectorizationRequirements;
+// A traits type that is intended to be used in graph algorithms. The graph it
+// models starts at the loop header, and traverses the BasicBlocks that are in
+// the loop body, but not the loop header. Since the loop header is skipped,
+// the back edges are excluded.
+struct LoopBodyTraits {
+ using NodeRef = std::pair<const Loop *, BasicBlock *>;
+
+ // This wraps a const Loop * into the iterator, so we know which edges to
+ // filter out.
+ class WrappedSuccIterator
+ : public iterator_adaptor_base<
+ WrappedSuccIterator, succ_iterator,
+ typename std::iterator_traits<succ_iterator>::iterator_category,
+ NodeRef, std::ptrdiff_t, NodeRef *, NodeRef> {
+ using BaseT = iterator_adaptor_base<
+ WrappedSuccIterator, succ_iterator,
+ typename std::iterator_traits<succ_iterator>::iterator_category,
+ NodeRef, std::ptrdiff_t, NodeRef *, NodeRef>;
+
+ const Loop *L;
+
+ public:
+ WrappedSuccIterator(succ_iterator Begin, const Loop *L)
+ : BaseT(Begin), L(L) {}
+
+ NodeRef operator*() const { return {L, *I}; }
+ };
+
+ struct LoopBodyFilter {
+ bool operator()(NodeRef N) const {
+ const Loop *L = N.first;
+ return N.second != L->getHeader() && L->contains(N.second);
+ }
+ };
+
+ using ChildIteratorType =
+ filter_iterator<WrappedSuccIterator, LoopBodyFilter>;
+
+ static NodeRef getEntryNode(const Loop &G) { return {&G, G.getHeader()}; }
+
+ static ChildIteratorType child_begin(NodeRef Node) {
+ return make_filter_range(make_range<WrappedSuccIterator>(
+ {succ_begin(Node.second), Node.first},
+ {succ_end(Node.second), Node.first}),
+ LoopBodyFilter{})
+ .begin();
+ }
+
+ static ChildIteratorType child_end(NodeRef Node) {
+ return make_filter_range(make_range<WrappedSuccIterator>(
+ {succ_begin(Node.second), Node.first},
+ {succ_end(Node.second), Node.first}),
+ LoopBodyFilter{})
+ .end();
+ }
+};
+
+/// Returns true if the given loop body has a cycle, excluding the loop
+/// itself.
+static bool hasCyclesInLoopBody(const Loop &L) {
+ if (!L.empty())
+ return true;
+
+ for (const auto SCC :
+ make_range(scc_iterator<Loop, LoopBodyTraits>::begin(L),
+ scc_iterator<Loop, LoopBodyTraits>::end(L))) {
+ if (SCC.size() > 1) {
+ DEBUG(dbgs() << "LVL: Detected a cycle in the loop body:\n");
+ DEBUG(L.dump());
+ return true;
+ }
+ }
+ return false;
+}
+
/// \brief This modifies LoopAccessReport to initialize message with
/// loop-vectorizer-specific part.
class VectorizationReport : public LoopAccessReport {
@@ -1843,12 +1919,14 @@ private:
OptimizationRemarkEmitter &ORE;
};
-static void addInnerLoop(Loop &L, SmallVectorImpl<Loop *> &V) {
- if (L.empty())
- return V.push_back(&L);
-
+static void addAcyclicInnerLoop(Loop &L, SmallVectorImpl<Loop *> &V) {
+ if (L.empty()) {
+ if (!hasCyclesInLoopBody(L))
+ V.push_back(&L);
+ return;
+ }
for (Loop *InnerL : L)
- addInnerLoop(*InnerL, V);
+ addAcyclicInnerLoop(*InnerL, V);
}
/// The LoopVectorize Pass.
@@ -4549,6 +4627,9 @@ bool LoopVectorizationLegality::canVecto
return false;
}
+ // FIXME: The code is currently dead, since the loop gets sent to
+ // LoopVectorizationLegality is already an innermost loop.
+ //
// We can only vectorize innermost loops.
if (!TheLoop->empty()) {
emitAnalysis(VectorizationReport() << "loop is not the innermost loop");
@@ -6800,7 +6881,7 @@ bool LoopVectorizePass::runImpl(
SmallVector<Loop *, 8> Worklist;
for (Loop *L : *LI)
- addInnerLoop(*L, Worklist);
+ addAcyclicInnerLoop(*L, Worklist);
LoopsAnalyzed += Worklist.size();
Added: llvm/trunk/test/Transforms/LoopVectorize/pr28541.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/pr28541.ll?rev=278573&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/pr28541.ll (added)
+++ llvm/trunk/test/Transforms/LoopVectorize/pr28541.ll Fri Aug 12 17:47:13 2016
@@ -0,0 +1,71 @@
+; RUN: opt -loop-vectorize -pass-remarks=loop-vectorize -S < %s 2>&1 | FileCheck %s
+
+; FIXME: Check for -pass-remarks-missed and -pass-remarks-analysis output when
+; addAcyclicInnerLoop emits analysis.
+
+; Check that opt does not crash on such input:
+;
+; a, b, c;
+; fn1() {
+; while (b--) {
+; c = a;
+; switch (a & 3)
+; case 0:
+; do
+; case 3:
+; case 2:
+; case 1:
+; ;
+; while (--c)
+; ;
+; }
+; }
+
+ at b = common global i32 0, align 4
+ at a = common global i32 0, align 4
+ at c = common global i32 0, align 4
+
+; CHECK-NOT: vectorized loop
+; CHECK-LABEL: fn1
+
+define i32 @fn1() {
+entry:
+ %tmp2 = load i32, i32* @b, align 4
+ %dec3 = add nsw i32 %tmp2, -1
+ store i32 %dec3, i32* @b, align 4
+ %tobool4 = icmp eq i32 %tmp2, 0
+ br i1 %tobool4, label %while.end, label %while.body.lr.ph
+
+while.body.lr.ph: ; preds = %entry
+ %tmp1 = load i32, i32* @a, align 4
+ %and = and i32 %tmp1, 3
+ %switch = icmp eq i32 %and, 0
+ br label %while.body
+
+while.cond: ; preds = %do.cond
+ %dec = add nsw i32 %dec7, -1
+ %tobool = icmp eq i32 %dec7, 0
+ br i1 %tobool, label %while.cond.while.end_crit_edge, label %while.body
+
+while.body: ; preds = %while.body.lr.ph, %while.cond
+ %dec7 = phi i32 [ %dec3, %while.body.lr.ph ], [ %dec, %while.cond ]
+ br i1 %switch, label %do.body, label %do.cond
+
+do.body: ; preds = %do.cond, %while.body
+ %dec25 = phi i32 [ %dec2, %do.cond ], [ %tmp1, %while.body ]
+ br label %do.cond
+
+do.cond: ; preds = %do.body, %while.body
+ %dec26 = phi i32 [ %dec25, %do.body ], [ %tmp1, %while.body ]
+ %dec2 = add nsw i32 %dec26, -1
+ %tobool3 = icmp eq i32 %dec2, 0
+ br i1 %tobool3, label %while.cond, label %do.body
+
+while.cond.while.end_crit_edge: ; preds = %while.cond
+ store i32 0, i32* @c, align 4
+ store i32 -1, i32* @b, align 4
+ br label %while.end
+
+while.end: ; preds = %while.cond.while.end_crit_edge, %entry
+ ret i32 undef
+}
More information about the llvm-commits
mailing list