[test][AArch64] Adjust vector insertion lit tests

[bjope]

The test cases test_insert_v16i8_insert_2_undef_base and test_insert_v16i8_insert_2_undef_base_different_valeus in CodeGen/AArch64/arm64-vector-insertion.ll was leaving element 8 in the vector as "undef" without any real explanation. It kind of looked like a typo as the input IR looked like this
%v.8 = insertelement <16 x i8> %v.7, i8 %a, i32 8
%v.10 = insertelement <16 x i8> %v.7, i8 %a, i32 10
leaving %v.8 as unused.

This patch is cleaning up the tests a bit by adding separate test cases to validate what is happening when skipping insert at index 8, while amending the original tests cases to use %v.8 instead of %v.7 when creating %v.10.

[llvmbot]

@llvm/pr-subscribers-backend-aarch64

Author: Björn Pettersson (bjope)

Changes

The test cases test_insert_v16i8_insert_2_undef_base and test_insert_v16i8_insert_2_undef_base_different_valeus in CodeGen/AArch64/arm64-vector-insertion.ll was leaving element 8 in the vector as "undef" without any real explanation. It kind of looked like a typo as the input IR looked like this
%v.8 = insertelement <16 x i8> %v.7, i8 %a, i32 8
%v.10 = insertelement <16 x i8> %v.7, i8 %a, i32 10
leaving %v.8 as unused.

This patch is cleaning up the tests a bit by adding separate test cases to validate what is happening when skipping insert at index 8, while amending the original tests cases to use %v.8 instead of %v.7 when creating %v.10.

---

Full diff: https://github.com/llvm/llvm-project/pull/143101.diff

1 Files Affected:

• (modified) llvm/test/CodeGen/AArch64/arm64-vector-insertion.ll (+65)

diff --git a/llvm/test/CodeGen/AArch64/arm64-vector-insertion.ll b/llvm/test/CodeGen/AArch64/arm64-vector-insertion.ll
index 94074d1689f6a..5962150ac9ffc 100644
--- a/llvm/test/CodeGen/AArch64/arm64-vector-insertion.ll
+++ b/llvm/test/CodeGen/AArch64/arm64-vector-insertion.ll
@@ -66,6 +66,35 @@ define <16 x i8> @test_insert_v16i8_insert_2_undef_base(i8 %a) {
   %v.6 = insertelement <16 x i8> %v.4, i8 %a, i32 6
   %v.7 = insertelement <16 x i8> %v.6, i8 %a, i32 7
   %v.8 = insertelement <16 x i8> %v.7, i8 %a, i32 8
+  %v.10 = insertelement <16 x i8> %v.8, i8 %a, i32 10
+  %v.11 = insertelement <16 x i8> %v.10, i8 %a, i32 11
+  %v.12 = insertelement <16 x i8> %v.11, i8 %a, i32 12
+  %v.13 = insertelement <16 x i8> %v.12, i8 %a, i32 13
+  %v.14 = insertelement <16 x i8> %v.13, i8 %a, i32 14
+  %v.15 = insertelement <16 x i8> %v.14, i8 %a, i32 15
+  ret <16 x i8> %v.15
+}
+
+; Similar to above, but we leave element 8 as undef. One interesting part with
+; this test case is that %a may be poison, so simply inserting %a also at
+; index 8 would make the result vector more poisonous.
+define <16 x i8> @test_insert_v16i8_insert_2_undef_base_skip8(i32 %a0) {
+; CHECK-LABEL: test_insert_v16i8_insert_2_undef_base_skip8:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    lsr w8, w0, #5
+; CHECK-NEXT:    dup.16b v0, w8
+; CHECK-NEXT:    mov.b v0[5], wzr
+; CHECK-NEXT:    mov.b v0[9], wzr
+; CHECK-NEXT:    ret
+  %a1 = lshr exact i32 %a0, 5
+  %a = trunc i32 %a1 to i8
+  %v.0 = insertelement <16 x i8> <i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 0, i8 undef, i8 undef, i8 undef, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef>  , i8 %a, i32 0
+  %v.1 = insertelement <16 x i8> %v.0, i8 %a, i32 1
+  %v.2 = insertelement <16 x i8> %v.1, i8 %a, i32 2
+  %v.3 = insertelement <16 x i8> %v.2, i8 %a, i32 3
+  %v.4 = insertelement <16 x i8> %v.3, i8 %a, i32 4
+  %v.6 = insertelement <16 x i8> %v.4, i8 %a, i32 6
+  %v.7 = insertelement <16 x i8> %v.6, i8 %a, i32 7
   %v.10 = insertelement <16 x i8> %v.7, i8 %a, i32 10
   %v.11 = insertelement <16 x i8> %v.10, i8 %a, i32 11
   %v.12 = insertelement <16 x i8> %v.11, i8 %a, i32 12
@@ -94,6 +123,42 @@ define <16 x i8> @test_insert_v16i8_insert_2_undef_base_different_valeus(i8 %a,
   %v.6 = insertelement <16 x i8> %v.4, i8 %a, i32 6
   %v.7 = insertelement <16 x i8> %v.6, i8 %b, i32 7
   %v.8 = insertelement <16 x i8> %v.7, i8 %a, i32 8
+  %v.10 = insertelement <16 x i8> %v.8, i8 %a, i32 10
+  %v.11 = insertelement <16 x i8> %v.10, i8 %a, i32 11
+  %v.12 = insertelement <16 x i8> %v.11, i8 %b, i32 12
+  %v.13 = insertelement <16 x i8> %v.12, i8 %a, i32 13
+  %v.14 = insertelement <16 x i8> %v.13, i8 %a, i32 14
+  %v.15 = insertelement <16 x i8> %v.14, i8 %b, i32 15
+  ret <16 x i8> %v.15
+}
+
+; Similar to above, but we leave element 8 as undef. One interesting part with
+; this test case is that %a and %b may be poison, so simply inserting %a or %b
+; at index 8 would make the result vector more poisonous.
+define <16 x i8> @test_insert_v16i8_insert_2_undef_base_different_valeus_skip8(i32 %a0, i32 %b0) {
+; CHECK-LABEL: test_insert_v16i8_insert_2_undef_base_different_valeus_skip8:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    lsr w8, w0, #5
+; CHECK-NEXT:    dup.16b v0, w8
+; CHECK-NEXT:    lsr w8, w1, #5
+; CHECK-NEXT:    mov.b v0[2], w8
+; CHECK-NEXT:    mov.b v0[5], wzr
+; CHECK-NEXT:    mov.b v0[7], w8
+; CHECK-NEXT:    mov.b v0[9], wzr
+; CHECK-NEXT:    mov.b v0[12], w8
+; CHECK-NEXT:    mov.b v0[15], w8
+; CHECK-NEXT:    ret
+  %a1 = lshr exact i32 %a0, 5
+  %a = trunc i32 %a1 to i8
+  %b1 = lshr exact i32 %b0, 5
+  %b = trunc i32 %b1 to i8
+  %v.0 = insertelement <16 x i8> <i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 0, i8 undef, i8 undef, i8 undef, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef>  , i8 %a, i32 0
+  %v.1 = insertelement <16 x i8> %v.0, i8 %a, i32 1
+  %v.2 = insertelement <16 x i8> %v.1, i8 %b, i32 2
+  %v.3 = insertelement <16 x i8> %v.2, i8 %a, i32 3
+  %v.4 = insertelement <16 x i8> %v.3, i8 %a, i32 4
+  %v.6 = insertelement <16 x i8> %v.4, i8 %a, i32 6
+  %v.7 = insertelement <16 x i8> %v.6, i8 %b, i32 7
   %v.10 = insertelement <16 x i8> %v.7, i8 %a, i32 10
   %v.11 = insertelement <16 x i8> %v.10, i8 %a, i32 11
   %v.12 = insertelement <16 x i8> %v.11, i8 %b, i32 12

[github-actions]

⚠️ undef deprecator found issues in your code. ⚠️

You can test this locally with the following command:

git diff -U0 --pickaxe-regex -S '([^a-zA-Z0-9#_-]undef[^a-zA-Z0-9_-]|UndefValue::get)' 'HEAD~1' HEAD llvm/test/CodeGen/AArch64/arm64-vector-insertion.ll

The following files introduce new uses of undef:

• llvm/test/CodeGen/AArch64/arm64-vector-insertion.ll

Undef is now deprecated and should only be used in the rare cases where no replacement is possible. For example, a load of uninitialized memory yields undef. You should use poison values for placeholders instead.

In tests, avoid using undef and having tests that trigger undefined behavior. If you need an operand with some unimportant value, you can add a new argument to the function and use that instead.

For example, this is considered a bad practice:

define void @fn() {
  ...
  br i1 undef, ...
}

Please use the following instead:

define void @fn(i1 %cond) {
  ...
  br i1 %cond, ...
}

Please refer to the Undefined Behavior Manual for more information.