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Don't vectorize if there are outside loop users of the induction variable.

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We would have to compute the pre increment value, either by computing it on
every loop iteration or by splitting the edge out of the loop and inserting a
computation for it there.

For now, just give up vectorizing such loops.

Fixes PR17179.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190790 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Arnold Schwaighofer 2013-09-16 16:17:24 +00:00
parent e5c8c5a1bc
commit 5721d2f674
2 changed files with 36 additions and 0 deletions
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6
lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -2866,6 +2866,12 @@ bool LoopVectorizationLegality::canVectorizeInstrs() {
DEBUG(dbgs() << "LV: Found an induction variable.\n");
Inductions[Phi] = InductionInfo(StartValue, IK);
// Until we explicitly handle the case of an induction variable with
// an outside loop user we have to give up vectorizing this loop.
if (hasOutsideLoopUser(TheLoop, it, AllowedExit))
return false;
continue;
}

30
test/Transforms/LoopVectorize/no_outside_user.ll
View File

@ -12,6 +12,7 @@ target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f3
; We used to vectorize this loop. But it has a value that is used outside of the
; and is not a recognized reduction variable "tmp17".
; CHECK-LABEL: main
; CHECK-NOT: <2 x i32>
define i32 @main() {
@ -38,4 +39,33 @@ f1.exit.loopexit:
ret i32 %.lcssa
}
; Don't vectorize this loop. Its phi node (induction variable) has an outside
; loop user. We currently don't handle this case.
; PR17179
; CHECK-LABEL: test2
; CHECK-NOT: <2 x
@x1 = common global i32 0, align 4
@x2 = common global i32 0, align 4
@x0 = common global i32 0, align 4
define i32 @test2() {
entry:
store i32 0, i32* @x1, align 4
%0 = load i32* @x0, align 4
br label %for.cond1.preheader
for.cond1.preheader:
%inc7 = phi i32 [ 0, %entry ], [ %inc, %for.cond1.preheader ]
%inc = add nsw i32 %inc7, 1
%cmp = icmp eq i32 %inc, 52
br i1 %cmp, label %for.end5, label %for.cond1.preheader
for.end5:
%inc7.lcssa = phi i32 [ %inc7, %for.cond1.preheader ]
%xor = xor i32 %inc7.lcssa, %0
store i32 52, i32* @x1, align 4
store i32 1, i32* @x2, align 4
ret i32 %xor
}