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LoopVectorizer: Don't assert on the absence of induction variables

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A computable loop exit count does not imply the presence of an induction
variable. Scalar evolution can return a value for an infinite loop.

Fixes PR15926.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181495 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Arnold Schwaighofer 2013-05-09 00:32:18 +00:00
parent 96e70b2a00
commit c121f5dc26
2 changed files with 36 additions and 1 deletions
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3
lib/Transforms/Vectorize/LoopVectorize.cpp
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@ -2523,7 +2523,8 @@ bool LoopVectorizationLegality::canVectorizeInstrs() {
if (!Induction) {
DEBUG(dbgs() << "LV: Did not find one integer induction var.\n");
assert(getInductionVars()->size() && "No induction variables");
if (Inductions.empty())
return false;
}
return true;

34
test/Transforms/LoopVectorize/infiniteloop.ll Normal file
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@ -0,0 +1,34 @@
; RUN: opt -S -indvars -loop-vectorize -force-vector-width=2 < %s | FileCheck %s
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32-S128"
@a = common global i64 0, align 8
@x = common global i32 0, align 4
; We used to assert on this loop because we could not find an induction
; variable but assumed there must be one. Scalar evolution returned a exit
; count for the loop below and from there on we assumed that there must be an
; induction variable. This is not a valid assumption:
; // getExitCount - Get the expression for the number of loop iterations for
; // which this loop is *guaranteed not to exit* via ExitingBlock. Otherwise
; // return SCEVCouldNotCompute.
; For an infinite loop SE can return any number.
; CHECK: fn1
define void @fn1() {
entry:
store i64 0, i64* @a, align 8
br label %for.body
for.body: ; preds = %for.body, %entry
%inc1 = phi i64 [ 0, %entry ], [ %inc, %for.body ]
store volatile i32 0, i32* @x, align 4
%inc = add nsw i64 %inc1, 1
%cmp = icmp sgt i64 %inc1, -2
br i1 %cmp, label %for.body, label %for.end
for.end: ; preds = %for.body
%inc.lcssa = phi i64 [ %inc, %for.body ]
store i64 %inc.lcssa, i64* @a, align 8
ret void
}