[polly] r248120 - Allow loops with multiple back edges
Johannes Doerfert via llvm-commits
llvm-commits at lists.llvm.org
Sun Sep 20 08:00:20 PDT 2015
Author: jdoerfert
Date: Sun Sep 20 10:00:20 2015
New Revision: 248120
URL: http://llvm.org/viewvc/llvm-project?rev=248120&view=rev
Log:
Allow loops with multiple back edges
In order to allow multiple back edges we:
- compute the conditions under which each back edge is taken
- build the union over all these conditions, thus the condition that
any back edge is taken
- apply the same logic to the union we applied to a single back edge
Added:
polly/trunk/test/ScopInfo/multiple_latch_blocks.ll
Modified:
polly/trunk/lib/Analysis/ScopDetection.cpp
polly/trunk/lib/Analysis/ScopInfo.cpp
Modified: polly/trunk/lib/Analysis/ScopDetection.cpp
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/Analysis/ScopDetection.cpp?rev=248120&r1=248119&r2=248120&view=diff
==============================================================================
--- polly/trunk/lib/Analysis/ScopDetection.cpp (original)
+++ polly/trunk/lib/Analysis/ScopDetection.cpp Sun Sep 20 10:00:20 2015
@@ -699,10 +699,6 @@ bool ScopDetection::isValidInstruction(I
bool ScopDetection::canUseISLTripCount(Loop *L,
DetectionContext &Context) const {
- // Ensure the loop has a single back edge.
- if (L->getNumBackEdges() != 1)
- return false;
-
// Ensure the loop has valid exiting blocks, otherwise we need to
// overapproximate it as a boxed loop.
SmallVector<BasicBlock *, 4> ExitingBlocks;
Modified: polly/trunk/lib/Analysis/ScopInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/Analysis/ScopInfo.cpp?rev=248120&r1=248119&r2=248120&view=diff
==============================================================================
--- polly/trunk/lib/Analysis/ScopInfo.cpp (original)
+++ polly/trunk/lib/Analysis/ScopInfo.cpp Sun Sep 20 10:00:20 2015
@@ -1913,28 +1913,7 @@ void Scop::addLoopBoundsToHeaderDomains(
int LoopDepth = getRelativeLoopDepth(L);
assert(LoopDepth >= 0 && "Loop in region should have at least depth one");
- BasicBlock *LatchBB = L->getLoopLatch();
- assert(LatchBB && "TODO implement multiple exit loop handling");
-
- isl_set *LatchBBDom = DomainMap[LatchBB];
- isl_set *BackedgeCondition = nullptr;
-
BasicBlock *HeaderBB = L->getHeader();
-
- BranchInst *BI = cast<BranchInst>(LatchBB->getTerminator());
- if (BI->isUnconditional())
- BackedgeCondition = isl_set_copy(LatchBBDom);
- else {
- SmallVector<isl_set *, 2> ConditionSets;
- int idx = BI->getSuccessor(0) != HeaderBB;
- buildConditionSets(*this, BI, L, LatchBBDom, ConditionSets);
-
- // Free the non back edge condition set as we do not need it.
- isl_set_free(ConditionSets[1 - idx]);
-
- BackedgeCondition = ConditionSets[idx];
- }
-
isl_set *&HeaderBBDom = DomainMap[HeaderBB];
isl_set *FirstIteration =
createFirstIterationDomain(isl_set_get_space(HeaderBBDom), LoopDepth);
@@ -1942,23 +1921,52 @@ void Scop::addLoopBoundsToHeaderDomains(
isl_map *NextIterationMap =
createNextIterationMap(isl_set_get_space(HeaderBBDom), LoopDepth);
- int LatchLoopDepth = getRelativeLoopDepth(LI.getLoopFor(LatchBB));
- assert(LatchLoopDepth >= LoopDepth);
- BackedgeCondition =
- isl_set_project_out(BackedgeCondition, isl_dim_set, LoopDepth + 1,
- LatchLoopDepth - LoopDepth);
+ isl_set *UnionBackedgeCondition =
+ isl_set_empty(isl_set_get_space(HeaderBBDom));
+
+ SmallVector<llvm::BasicBlock *, 4> LatchBlocks;
+ L->getLoopLatches(LatchBlocks);
+
+ for (BasicBlock *LatchBB : LatchBlocks) {
+ assert(DomainMap.count(LatchBB));
+ isl_set *LatchBBDom = DomainMap[LatchBB];
+ isl_set *BackedgeCondition = nullptr;
+
+ BranchInst *BI = cast<BranchInst>(LatchBB->getTerminator());
+ if (BI->isUnconditional())
+ BackedgeCondition = isl_set_copy(LatchBBDom);
+ else {
+ SmallVector<isl_set *, 2> ConditionSets;
+ int idx = BI->getSuccessor(0) != HeaderBB;
+ buildConditionSets(*this, BI, L, LatchBBDom, ConditionSets);
+
+ // Free the non back edge condition set as we do not need it.
+ isl_set_free(ConditionSets[1 - idx]);
+
+ BackedgeCondition = ConditionSets[idx];
+ }
+
+ int LatchLoopDepth = getRelativeLoopDepth(LI.getLoopFor(LatchBB));
+ assert(LatchLoopDepth >= LoopDepth);
+ BackedgeCondition =
+ isl_set_project_out(BackedgeCondition, isl_dim_set, LoopDepth + 1,
+ LatchLoopDepth - LoopDepth);
+ UnionBackedgeCondition =
+ isl_set_union(UnionBackedgeCondition, BackedgeCondition);
+ }
isl_map *ForwardMap = isl_map_lex_le(isl_set_get_space(HeaderBBDom));
for (int i = 0; i < LoopDepth; i++)
ForwardMap = isl_map_equate(ForwardMap, isl_dim_in, i, isl_dim_out, i);
- isl_set *BackedgeConditionComplement =
- isl_set_complement(BackedgeCondition);
- BackedgeConditionComplement = isl_set_lower_bound_si(
- BackedgeConditionComplement, isl_dim_set, LoopDepth, 0);
- BackedgeConditionComplement =
- isl_set_apply(BackedgeConditionComplement, ForwardMap);
- HeaderBBDom = isl_set_subtract(HeaderBBDom, BackedgeConditionComplement);
+ isl_set *UnionBackedgeConditionComplement =
+ isl_set_complement(UnionBackedgeCondition);
+ UnionBackedgeConditionComplement = isl_set_lower_bound_si(
+ UnionBackedgeConditionComplement, isl_dim_set, LoopDepth, 0);
+ UnionBackedgeConditionComplement =
+ isl_set_apply(UnionBackedgeConditionComplement, ForwardMap);
+ HeaderBBDom =
+ isl_set_subtract(HeaderBBDom, UnionBackedgeConditionComplement);
auto Parts = partitionSetParts(HeaderBBDom, LoopDepth);
Added: polly/trunk/test/ScopInfo/multiple_latch_blocks.ll
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/test/ScopInfo/multiple_latch_blocks.ll?rev=248120&view=auto
==============================================================================
--- polly/trunk/test/ScopInfo/multiple_latch_blocks.ll (added)
+++ polly/trunk/test/ScopInfo/multiple_latch_blocks.ll Sun Sep 20 10:00:20 2015
@@ -0,0 +1,47 @@
+; RUN: opt %loadPolly -analyze -polly-scops -polly-detect-unprofitable < %s | FileCheck %s
+;
+; CHECK: Domain :=
+; CHECK: [N, P] -> { Stmt_if_end[i0] : (i0 >= 1 + P and i0 >= 0 and i0 <= -1 + N) or (i0 >= 0 and i0 <= -1 + P and i0 <= -1 + N) };
+;
+; void f(int *A, int N, int P, int Q) {
+; for (int i = 0; i < N; i++) {
+; if (i == P)
+; continue;
+; A[i]++;
+; }
+; }
+;
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @f(i32* %A, i32 %N, i32 %P, i32 %Q) {
+entry:
+ %tmp = sext i32 %N to i64
+ br label %for.cond
+
+for.cond: ; preds = %for.inc, %entry
+ %indvars.iv = phi i64 [ %indvars.iv.next, %if.then ], [ %indvars.iv.next, %for.inc ], [ 0, %entry ]
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %cmp = icmp slt i64 %indvars.iv, %tmp
+ br i1 %cmp, label %for.body, label %for.end
+
+for.body: ; preds = %for.cond
+ %tmp1 = trunc i64 %indvars.iv to i32
+ %cmp1 = icmp eq i32 %tmp1, %P
+ br i1 %cmp1, label %if.then, label %if.end
+
+if.then: ; preds = %for.body
+ br label %for.cond
+
+if.end: ; preds = %for.body
+ %arrayidx = getelementptr inbounds i32, i32* %A, i64 %indvars.iv
+ %tmp2 = load i32, i32* %arrayidx, align 4
+ %inc = add nsw i32 %tmp2, 1
+ store i32 %inc, i32* %arrayidx, align 4
+ br label %for.inc
+
+for.inc: ; preds = %if.end, %if.then
+ br label %for.cond
+
+for.end: ; preds = %for.cond
+ ret void
+}
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