[llvm] c491949 - [LV] Pick correct BB as insert point when fixing PHI for FORs.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Sat Dec 7 11:33:00 PST 2019
Author: Florian Hahn
Date: 2019-12-07T19:32:00Z
New Revision: c49194969430f0ee817498a7000a979a7a0ded03
URL: https://github.com/llvm/llvm-project/commit/c49194969430f0ee817498a7000a979a7a0ded03
DIFF: https://github.com/llvm/llvm-project/commit/c49194969430f0ee817498a7000a979a7a0ded03.diff
LOG: [LV] Pick correct BB as insert point when fixing PHI for FORs.
Currently we fail to pick the right insertion point when
PreviousLastPart of a first-order-recurrence is a PHI node not in the
LoopVectorBody. This can happen when PreviousLastPart is produce in a
predicated block. In that case, we should pick the insertion point in
the BB the PHI is in.
Fixes PR44020.
Reviewers: hsaito, fhahn, Ayal, dorit
Reviewed By: Ayal
Differential Revision: https://reviews.llvm.org/D71071
Added:
llvm/test/Transforms/LoopVectorize/SystemZ/predicated-first-order-recurrence.ll
Modified:
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 3d21c9353e62..dd9b44a1c8e8 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -3556,17 +3556,27 @@ void InnerLoopVectorizer::fixFirstOrderRecurrence(PHINode *Phi) {
// among all unrolled iterations, due to the order of their construction.
Value *PreviousLastPart = getOrCreateVectorValue(Previous, UF - 1);
- // Set the insertion point after the previous value if it is an instruction.
+ // Find and set the insertion point after the previous value if it is an
+ // instruction.
+ BasicBlock::iterator InsertPt;
// Note that the previous value may have been constant-folded so it is not
- // guaranteed to be an instruction in the vector loop. Also, if the previous
- // value is a phi node, we should insert after all the phi nodes to avoid
- // breaking basic block verification.
- if (LI->getLoopFor(LoopVectorBody)->isLoopInvariant(PreviousLastPart) ||
- isa<PHINode>(PreviousLastPart))
- Builder.SetInsertPoint(&*LoopVectorBody->getFirstInsertionPt());
- else
- Builder.SetInsertPoint(
- &*++BasicBlock::iterator(cast<Instruction>(PreviousLastPart)));
+ // guaranteed to be an instruction in the vector loop.
+ // FIXME: Loop invariant values do not form recurrences. We should deal with
+ // them earlier.
+ if (LI->getLoopFor(LoopVectorBody)->isLoopInvariant(PreviousLastPart))
+ InsertPt = LoopVectorBody->getFirstInsertionPt();
+ else {
+ Instruction *PreviousInst = cast<Instruction>(PreviousLastPart);
+ if (isa<PHINode>(PreviousLastPart))
+ // If the previous value is a phi node, we should insert after all the phi
+ // nodes in the block containing the PHI to avoid breaking basic block
+ // verification. Note that the basic block may be
diff erent to
+ // LoopVectorBody, in case we predicate the loop.
+ InsertPt = PreviousInst->getParent()->getFirstInsertionPt();
+ else
+ InsertPt = ++PreviousInst->getIterator();
+ }
+ Builder.SetInsertPoint(&*InsertPt);
// We will construct a vector for the recurrence by combining the values for
// the current and previous iterations. This is the required shuffle mask.
diff --git a/llvm/test/Transforms/LoopVectorize/SystemZ/predicated-first-order-recurrence.ll b/llvm/test/Transforms/LoopVectorize/SystemZ/predicated-first-order-recurrence.ll
new file mode 100644
index 000000000000..7c5b5c53e931
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/SystemZ/predicated-first-order-recurrence.ll
@@ -0,0 +1,103 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -loop-vectorize -mtriple=s390x-ibm-linux -mcpu=z13 -force-vector-width=2 -S %s | FileCheck %s
+
+; Test case from PR44020.
+
+; In func_21, %rec forms a first order recurrence and we predicate to avoid
+; scalar iteration overhead for a low trip count loop. Make sure we pick
+; the correct insertion point when fixing first order recurrences.
+
+ at A = external dso_local global [5 x i32], align 4
+ at B = external dso_local global [5 x i32], align 4
+
+define void @func_21() {
+; CHECK-LABEL: @func_21(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK: vector.ph:
+; CHECK-NEXT: br label [[VECTOR_BODY:%.*]]
+; CHECK: vector.body:
+; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[PRED_STORE_CONTINUE4:%.*]] ]
+; CHECK-NEXT: [[VECTOR_RECUR:%.*]] = phi <2 x i32> [ <i32 undef, i32 0>, [[VECTOR_PH]] ], [ [[TMP12:%.*]], [[PRED_STORE_CONTINUE4]] ]
+; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x i64> undef, i64 [[INDEX]], i32 0
+; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <2 x i64> [[BROADCAST_SPLATINSERT]], <2 x i64> undef, <2 x i32> zeroinitializer
+; CHECK-NEXT: [[INDUCTION:%.*]] = add <2 x i64> [[BROADCAST_SPLAT]], <i64 0, i64 1>
+; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[INDEX]], 0
+; CHECK-NEXT: [[TMP1:%.*]] = add i64 [[INDEX]], 1
+; CHECK-NEXT: [[TMP2:%.*]] = icmp ule <2 x i64> [[INDUCTION]], <i64 4, i64 4>
+; CHECK-NEXT: [[TMP3:%.*]] = extractelement <2 x i1> [[TMP2]], i32 0
+; CHECK-NEXT: br i1 [[TMP3]], label [[PRED_LOAD_IF:%.*]], label [[PRED_LOAD_CONTINUE:%.*]]
+; CHECK: pred.load.if:
+; CHECK-NEXT: [[TMP4:%.*]] = getelementptr inbounds [5 x i32], [5 x i32]* @A, i64 0, i64 [[TMP0]]
+; CHECK-NEXT: [[TMP5:%.*]] = load i32, i32* [[TMP4]], align 4
+; CHECK-NEXT: [[TMP6:%.*]] = insertelement <2 x i32> undef, i32 [[TMP5]], i32 0
+; CHECK-NEXT: br label [[PRED_LOAD_CONTINUE]]
+; CHECK: pred.load.continue:
+; CHECK-NEXT: [[TMP7:%.*]] = phi <2 x i32> [ undef, [[VECTOR_BODY]] ], [ [[TMP6]], [[PRED_LOAD_IF]] ]
+; CHECK-NEXT: [[TMP8:%.*]] = extractelement <2 x i1> [[TMP2]], i32 1
+; CHECK-NEXT: br i1 [[TMP8]], label [[PRED_LOAD_IF1:%.*]], label [[PRED_LOAD_CONTINUE2:%.*]]
+; CHECK: pred.load.if1:
+; CHECK-NEXT: [[TMP9:%.*]] = getelementptr inbounds [5 x i32], [5 x i32]* @A, i64 0, i64 [[TMP1]]
+; CHECK-NEXT: [[TMP10:%.*]] = load i32, i32* [[TMP9]], align 4
+; CHECK-NEXT: [[TMP11:%.*]] = insertelement <2 x i32> [[TMP7]], i32 [[TMP10]], i32 1
+; CHECK-NEXT: br label [[PRED_LOAD_CONTINUE2]]
+; CHECK: pred.load.continue2:
+; CHECK-NEXT: [[TMP12]] = phi <2 x i32> [ [[TMP7]], [[PRED_LOAD_CONTINUE]] ], [ [[TMP11]], [[PRED_LOAD_IF1]] ]
+; CHECK-NEXT: [[TMP13:%.*]] = shufflevector <2 x i32> [[VECTOR_RECUR]], <2 x i32> [[TMP12]], <2 x i32> <i32 1, i32 2>
+; CHECK-NEXT: [[TMP14:%.*]] = extractelement <2 x i1> [[TMP2]], i32 0
+; CHECK-NEXT: br i1 [[TMP14]], label [[PRED_STORE_IF:%.*]], label [[PRED_STORE_CONTINUE:%.*]]
+; CHECK: pred.store.if:
+; CHECK-NEXT: [[TMP15:%.*]] = getelementptr inbounds [5 x i32], [5 x i32]* @B, i64 0, i64 [[TMP0]]
+; CHECK-NEXT: [[TMP16:%.*]] = extractelement <2 x i32> [[TMP13]], i32 0
+; CHECK-NEXT: store i32 [[TMP16]], i32* [[TMP15]], align 4
+; CHECK-NEXT: br label [[PRED_STORE_CONTINUE]]
+; CHECK: pred.store.continue:
+; CHECK-NEXT: [[TMP17:%.*]] = extractelement <2 x i1> [[TMP2]], i32 1
+; CHECK-NEXT: br i1 [[TMP17]], label [[PRED_STORE_IF3:%.*]], label [[PRED_STORE_CONTINUE4]]
+; CHECK: pred.store.if3:
+; CHECK-NEXT: [[TMP18:%.*]] = getelementptr inbounds [5 x i32], [5 x i32]* @B, i64 0, i64 [[TMP1]]
+; CHECK-NEXT: [[TMP19:%.*]] = extractelement <2 x i32> [[TMP13]], i32 1
+; CHECK-NEXT: store i32 [[TMP19]], i32* [[TMP18]], align 4
+; CHECK-NEXT: br label [[PRED_STORE_CONTINUE4]]
+; CHECK: pred.store.continue4:
+; CHECK-NEXT: [[INDEX_NEXT]] = add i64 [[INDEX]], 2
+; CHECK-NEXT: [[TMP20:%.*]] = icmp eq i64 [[INDEX_NEXT]], 6
+; CHECK-NEXT: br i1 [[TMP20]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop !0
+; CHECK: middle.block:
+; CHECK-NEXT: [[VECTOR_RECUR_EXTRACT:%.*]] = extractelement <2 x i32> [[TMP12]], i32 1
+; CHECK-NEXT: [[VECTOR_RECUR_EXTRACT_FOR_PHI:%.*]] = extractelement <2 x i32> [[TMP12]], i32 0
+; CHECK-NEXT: br i1 true, label [[EXIT:%.*]], label [[SCALAR_PH]]
+; CHECK: scalar.ph:
+; CHECK-NEXT: [[SCALAR_RECUR_INIT:%.*]] = phi i32 [ [[VECTOR_RECUR_EXTRACT]], [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ 6, [[MIDDLE_BLOCK]] ], [ 0, [[ENTRY]] ]
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: [[SCALAR_RECUR:%.*]] = phi i32 [ [[SCALAR_RECUR_INIT]], [[SCALAR_PH]] ], [ [[LV:%.*]], [[LOOP]] ]
+; CHECK-NEXT: [[INDVARS_IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[INDVARS_IV_NEXT:%.*]], [[LOOP]] ]
+; CHECK-NEXT: [[A_PTR:%.*]] = getelementptr inbounds [5 x i32], [5 x i32]* @A, i64 0, i64 [[INDVARS_IV]]
+; CHECK-NEXT: [[LV]] = load i32, i32* [[A_PTR]], align 4
+; CHECK-NEXT: [[B_PTR:%.*]] = getelementptr inbounds [5 x i32], [5 x i32]* @B, i64 0, i64 [[INDVARS_IV]]
+; CHECK-NEXT: store i32 [[SCALAR_RECUR]], i32* [[B_PTR]], align 4
+; CHECK-NEXT: [[INDVARS_IV_NEXT]] = add nuw nsw i64 [[INDVARS_IV]], 1
+; CHECK-NEXT: [[EXITCOND:%.*]] = icmp eq i64 [[INDVARS_IV_NEXT]], 5
+; CHECK-NEXT: br i1 [[EXITCOND]], label [[EXIT]], label [[LOOP]], !llvm.loop !2
+; CHECK: exit:
+; CHECK-NEXT: ret void
+;
+entry:
+ br label %loop
+
+loop: ; preds = %loop, %entry
+ %rec = phi i32 [ 0, %entry], [ %lv, %loop ]
+ %indvars.iv = phi i64 [ 0, %entry], [ %indvars.iv.next, %loop ]
+ %A.ptr= getelementptr inbounds [5 x i32], [5 x i32]* @A, i64 0, i64 %indvars.iv
+ %lv = load i32, i32* %A.ptr, align 4
+ %B.ptr = getelementptr inbounds [5 x i32], [5 x i32]* @B, i64 0, i64 %indvars.iv
+ store i32 %rec, i32* %B.ptr, align 4
+ %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+ %exitcond = icmp eq i64 %indvars.iv.next, 5
+ br i1 %exitcond, label %exit, label %loop
+
+exit: ; preds = %loop
+ ret void
+}
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