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[LV] Fix insertion point for shuffle vectors in first order recurrence

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Summary:
In first order recurrence vectorization, when the previous value is a phi node, we need to
set the insertion point to the first non-phi node.
We can have the previous value being a phi node, due to the generation of new
IVs as part of trunc optimization [1].

[1] https://reviews.llvm.org/rL294967

Reviewers: mssimpso, mkuper

Subscribers: mzolotukhin, llvm-commits

Differential Revision: https://reviews.llvm.org/D32969

llvm-svn: 302532
This commit is contained in:
Anna Thomas 2017-05-09 14:29:33 +00:00
parent f74a6f060f
commit 3580c4d010
2 changed files with 50 additions and 2 deletions
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7
lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -4052,8 +4052,11 @@ void InnerLoopVectorizer::fixFirstOrderRecurrence(PHINode *Phi) {
// Set the insertion point after the previous value if it is an instruction.
// Note that the previous value may have been constant-folded so it is not
// guaranteed to be an instruction in the vector loop.
if (LI->getLoopFor(LoopVectorBody)->isLoopInvariant(PreviousParts[UF - 1]))
// 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(PreviousParts[UF - 1]) ||
isa<PHINode>(PreviousParts[UF - 1]))
Builder.SetInsertPoint(&*LoopVectorBody->getFirstInsertionPt());
else
Builder.SetInsertPoint(

45
test/Transforms/LoopVectorize/induction.ll
View File

@ -849,3 +849,48 @@ for.end:
%tmp7 = phi i32 [ %tmp6, %for.inc ]
ret i32 %tmp7
}
; Ensure that the shuffle vector for first order recurrence is inserted
; correctly after all the phis. These new phis correspond to new IVs
; that are generated by optimizing non-free truncs of IVs to IVs themselves
define i64 @trunc_with_first_order_recurrence() {
; CHECK-LABEL: trunc_with_first_order_recurrence
; CHECK-LABEL: vector.body:
; CHECK-NEXT: %index = phi i64 [ 0, %vector.ph ], [ %index.next, %vector.body ]
; CHECK-NEXT: %vec.phi = phi <2 x i64>
; CHECK-NEXT: %vec.ind = phi <2 x i64> [ <i64 1, i64 2>, %vector.ph ], [ %vec.ind.next, %vector.body ]
; CHECK-NEXT: %vec.ind2 = phi <2 x i32> [ <i32 1, i32 2>, %vector.ph ], [ %vec.ind.next3, %vector.body ]
; CHECK-NEXT: %vector.recur = phi <2 x i32> [ <i32 undef, i32 42>, %vector.ph ], [ %vec.ind5, %vector.body ]
; CHECK-NEXT: %vec.ind5 = phi <2 x i32> [ <i32 1, i32 2>, %vector.ph ], [ %vec.ind.next6, %vector.body ]
; CHECK-NEXT: %vec.ind7 = phi <2 x i32> [ <i32 1, i32 2>, %vector.ph ], [ %vec.ind.next8, %vector.body ]
; CHECK-NEXT: shufflevector <2 x i32> %vector.recur, <2 x i32> %vec.ind5, <2 x i32> <i32 1, i32 2>
entry:
br label %loop
exit: ; preds = %loop
%.lcssa = phi i64 [ %c23, %loop ]
ret i64 %.lcssa
loop: ; preds = %loop, %entry
%c5 = phi i64 [ %c23, %loop ], [ 0, %entry ]
%indvars.iv = phi i64 [ %indvars.iv.next, %loop ], [ 1, %entry ]
%x = phi i32 [ %c24, %loop ], [ 1, %entry ]
%y = phi i32 [ %c6, %loop ], [ 42, %entry ]
%c6 = trunc i64 %indvars.iv to i32
%c8 = mul i32 %x, %c6
%c9 = add i32 %c8, 42
%c10 = add i32 %y, %c6
%c11 = add i32 %c10, %c9
%c12 = sext i32 %c11 to i64
%c13 = add i64 %c5, %c12
%indvars.iv.tr = trunc i64 %indvars.iv to i32
%c14 = shl i32 %indvars.iv.tr, 1
%c15 = add i32 %c9, %c14
%c16 = sext i32 %c15 to i64
%c23 = add i64 %c13, %c16
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%c24 = add nuw nsw i32 %x, 1
%exitcond.i = icmp eq i64 %indvars.iv.next, 114
br i1 %exitcond.i, label %exit, label %loop
}