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authorArnold Schwaighofer <aschwaighofer@apple.com>2013-04-12 15:15:19 +0000
committerArnold Schwaighofer <aschwaighofer@apple.com>2013-04-12 15:15:19 +0000
commit08a0e8f8dbae6314dade60e1ef92e73e89c5ff23 (patch)
treec92a7deba86db295ab34ac2acbcd84ed94d77325 /test/Transforms
parentb6ad2bd51195f7675db0f71c5826a12a2b7090fc (diff)
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LoopVectorizer: integer division is not a reduction operation
Don't classify idiv/udiv as a reduction operation. Integer division is lossy. For example : (1 / 2) * 4 != 4/2. Example: int a[] = { 2, 5, 2, 2} int x = 80; for() x /= a[i]; Scalar: x /= 2 // = 40 x /= 5 // = 8 x /= 2 // = 4 x /= 2 // = 2 Vectorized: <80, 1> / <2,5> //= <40,0> <40, 0> / <2,2> //= <20,0> 20*0 = 0 radar://13640654 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179381 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test/Transforms')
-rw-r--r--test/Transforms/LoopVectorize/no_idiv_reduction.ll24
1 files changed, 24 insertions, 0 deletions
diff --git a/test/Transforms/LoopVectorize/no_idiv_reduction.ll b/test/Transforms/LoopVectorize/no_idiv_reduction.ll
new file mode 100644
index 0000000..cdfb3fd
--- /dev/null
+++ b/test/Transforms/LoopVectorize/no_idiv_reduction.ll
@@ -0,0 +1,24 @@
+; RUN: opt -loop-vectorize -force-vector-width=2 -force-vector-unroll=1 -S < %s | FileCheck %s
+@a = common global [128 x i32] zeroinitializer, align 16
+
+;; Must not vectorize division reduction. Division is lossy.
+define i32 @g() {
+entry:
+ br label %for.body
+
+for.body:
+ ; CHECK: @g
+ ; CHECK-NOT: sdiv <2 x i32>
+ %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+ %r.05 = phi i32 [ 80, %entry ], [ %div, %for.body ]
+ %arrayidx = getelementptr inbounds [128 x i32]* @a, i64 0, i64 %indvars.iv
+ %0 = load i32* %arrayidx, align 4
+ %div = sdiv i32 %r.05, %0
+ %indvars.iv.next = add i64 %indvars.iv, 1
+ %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+ %exitcond = icmp eq i32 %lftr.wideiv, 1024
+ br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+ ret i32 %div
+}