[PATCH] D21773: [clang] Update an optimization remark test for change D18777

[Li Huang via cfe-commits]

lihuang created this revision.
lihuang added reviewers: sanjoy, reames.
lihuang added a subscriber: cfe-commits.

Update an optimization remark test for change D18777.

This test checks the loop-vectorization remarks when pointer checking threshold 
is exceeded. The change in D18777 would introduce zexts that cannot be removed 
so that the "loop not vectorized" reason is changed, hence breaking this test. 

Modified the offsets to be 1 and the zexts could be finally removed by indvars 
(this magic fact is attributed to some scev mechanisms). Since the purpose of 
this test is checking the vectorization options, the offset numbers don't 
matter. 

http://reviews.llvm.org/D21773

Files:
  test/Frontend/optimization-remark-options.c

Index: test/Frontend/optimization-remark-options.c
===
--- test/Frontend/optimization-remark-options.c
+++ test/Frontend/optimization-remark-options.c
@@ -16,6 +16,6 @@
 void foo2(int *dw, int *uw, int *A, int *B, int *C, int *D, int N) {
   for (int i = 0; i < N; i++) {
 dw[i] = A[i] + B[i - 1] + C[i - 2] + D[i - 3];
-uw[i] = A[i] + B[i + 1] + C[i + 2] + D[i + 3];
+uw[i] = A[i] + B[i + 1] + C[i + 1] + D[i + 1];
   }
 }


Index: test/Frontend/optimization-remark-options.c
===
--- test/Frontend/optimization-remark-options.c
+++ test/Frontend/optimization-remark-options.c
@@ -16,6 +16,6 @@
 void foo2(int *dw, int *uw, int *A, int *B, int *C, int *D, int N) {
   for (int i = 0; i < N; i++) {
 dw[i] = A[i] + B[i - 1] + C[i - 2] + D[i - 3];
-uw[i] = A[i] + B[i + 1] + C[i + 2] + D[i + 3];
+uw[i] = A[i] + B[i + 1] + C[i + 1] + D[i + 1];
   }
 }
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Re: [PATCH] D21773: [clang] Update an optimization remark test for change D18777

[Li Huang via cfe-commits]

lihuang added a comment.

Hi Adam,

The change in http://reviews.llvm.org/D18777 breaks this test becasue it 
converts some sexts to zexts, which cannot be eliminated by 
indvar-simplification after widening IV.

The IR after indvar-simplification and before loop-vectorization is like:

  ...
  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, 
%for.body.preheader ]
  ...
  add nuw nsw i64 %indvars.iv, 2  // i + 2
  %12 = trunc i64 %11 to i32
  %idxprom2047 = zext i32 %12 to i64
  %arrayidx21 = getelementptr inbounds i32, i32* %C, i64 %idxprom2047
  ...
  %14 = add nuw nsw i64 %indvars.iv, 3// i + 3
  %15 = trunc i64 %14 to i32
  %idxprom2448 = zext i32 %15 to i64
  ...

IV is promoted to 64-bit but the trunc/zext cannot be eliminated (at least 
cannot be eliminated with the -O1 pass pipeline). Then optimzation remark 
becomes:

  optimization-remark-options.c:17:3: remark: loop not vectorized: cannot 
identify array bounds
 [-Rpass-analysis=loop-vectorize]
  for (int i = 0; i < N; i++) {


http://reviews.llvm.org/D21773



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Re: [PATCH] D21773: [clang] Update an optimization remark test for change D18777

[Li Huang via cfe-commits]

lihuang added a comment.

You are right. A regression test could be:

  void foo2(int *dw, int *uw, int *A, int *B, int *C, int *D, int N) {
for (int i = 0; i < N; i++) {
  dw[i] = A[i] + B[i - 1] + C[i - 2];
  uw[i] = A[i] + B[i + 2];
}
  }

need to fix the fundamental problem.


http://reviews.llvm.org/D21773



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