[clang][CodeGen] Fix metadata when vectorization is disabled by pragma

There are two ways to disable vectorization with pragma,
`vectorize(disable)` and `vectorize_width(1)`. The document
(https://clang.llvm.org/docs/LanguageExtensions.html#vectorization-interleaving-and-predication)
states:

> Specifying a width/count of 1 disables the optimization, and is
equivalent to `vectorize(disable)` or `interleave(disable)`.

So the behavior should be the same when using either is used. However,
the current implementation doesn't satisfy this. When
`vectorize(disable)` is specified, it is converted internally to the
same as `vectorize_width(1)`, and the metadata is generated as if
vectorization is not explicitly specified as enabled or disabled. This
can cause a problem when other transformations are also specified by
pragma. For example, if `unroll_count(8)` is specified, the loop should
have a metadata that contains the information directly, like:

```
!loop0 = !{!"loop0", !vectorize_disable, !unroll}
!vectorize_disable = {...}
!unroll = !{!"llvm.loop.unroll_count", i32 8}
```

But now it's attached into followup metadata for vectorization.

```
!loop0 = !{!"loop0", !vectorize_width, !followup}
!vectorize_width = !{!"llvm.loop.vectorize.width", i32 1}
!followup = !{!"llvm.loop.vectorize.followup_all", !unroll}
!unroll = !{!"llvm.loop.unroll_count", i32 8}
```

As a result, the unroll attributes are ignored because the vectorization
is not applied.

This patch fixes this issue by generating metadata that disables
vectorization when `vectorize(disable)` or `vectorize_width(1)` are
specified.

The document also says:

> If the transformation is disabled (e.g. vectorize(disable)), that
takes precedence over transformations option pragmas implying that
transformation.

Therefore, if vectorization is disabled, all other vectorize options
like `vectorize_predicate` should be ignored. This patch also omits to
generate attributes for vectorization when it is disabled.

Fix #75839

Author: kasuga-fj

clang/lib/CodeGen/CGLoopInfo.cpp

@@ -200,7 +200,8 @@ LoopInfo::createLoopVectorizeMetadata(const LoopAttributes &Attrs,
   LLVMContext &Ctx = Header->getContext();
 
   std::optional<bool> Enabled;
-  if (Attrs.VectorizeEnable == LoopAttributes::Disable)
+  if (Attrs.VectorizeEnable == LoopAttributes::Disable ||
+      Attrs.VectorizeWidth == 1)
     Enabled = false;
   else if (Attrs.VectorizeEnable != LoopAttributes::Unspecified ||
            Attrs.VectorizePredicateEnable != LoopAttributes::Unspecified ||
@@ -643,9 +644,7 @@ void LoopInfoStack::push(BasicBlock *Header, clang::ASTContext &Ctx,
     case LoopHintAttr::Disable:
       switch (Option) {
       case LoopHintAttr::Vectorize:
-        // Disable vectorization by specifying a width of 1.
-        setVectorizeWidth(1);
-        setVectorizeScalable(LoopAttributes::Unspecified);
+        setVectorizeEnable(false);
         break;
       case LoopHintAttr::Interleave:
         // Disable interleaving by speciyfing a count of 1.

clang/test/CodeGenCXX/pragma-loop-pr27643.cpp

@@ -40,14 +40,14 @@ void loop4(int *List, int Length) {
     List[i] = i * 2;
 }
 
-// CHECK: ![[LOOP1]] = distinct !{![[LOOP1]], [[MP:![0-9]+]], ![[VEC_WIDTH_1:.*]], ![[FIXED_WIDTH:.*]], ![[VEC_ENABLE:.*]]}
-// CHECK: ![[VEC_WIDTH_1]] = !{!"llvm.loop.vectorize.width", i32 1}
-// CHECK: ![[FIXED_WIDTH]] = !{!"llvm.loop.vectorize.scalable.enable", i1 false}
-// CHECK: ![[VEC_ENABLE]] = !{!"llvm.loop.vectorize.enable", i1 true}
+// CHECK: ![[LOOP1]] = distinct !{![[LOOP1]], [[MP:![0-9]+]], ![[VEC_DISABLE:[0-9]+]]}
+// CHECK: ![[VEC_DISABLE]] = !{!"llvm.loop.vectorize.enable", i1 false}
 
-// CHECK: ![[LOOP2]] = distinct !{![[LOOP2]], [[MP]], ![[VEC_WIDTH_2:.*]], ![[FIXED_WIDTH:.*]], ![[VEC_ENABLE]]}
+// CHECK: ![[LOOP2]] = distinct !{![[LOOP2]], [[MP]], ![[VEC_WIDTH_2:.*]], ![[FIXED_WIDTH:[0-9]+]], ![[VEC_ENABLE:[0-9]+]]}
 // CHECK: ![[VEC_WIDTH_2]] = !{!"llvm.loop.vectorize.width", i32 2}
+// CHECK: ![[FIXED_WIDTH]] = !{!"llvm.loop.vectorize.scalable.enable", i1 false}
+// CHECK: ![[VEC_ENABLE]] = !{!"llvm.loop.vectorize.enable", i1 true}
 
-// CHECK: ![[LOOP3]] = distinct !{![[LOOP3]], [[MP]], ![[VEC_WIDTH_1]], ![[FIXED_WIDTH]]}
+// CHECK: ![[LOOP3]] = distinct !{![[LOOP3]], [[MP]], ![[VEC_DISABLE]]}
 
 // CHECK: ![[LOOP4]] = distinct !{![[LOOP4]], [[MP]], ![[VEC_WIDTH_2]], ![[FIXED_WIDTH]], ![[VEC_ENABLE]]}

clang/test/CodeGenCXX/pragma-loop-predicate.cpp

@@ -37,8 +37,8 @@ void test3(int *List, int Length) {
     List[i] = i * 2;
 }
 
-// Check that disabling vectorization means a vectorization width of 1, and
-// also that vectorization_predicate isn't enabled.
+// Check that vectorize is disabled, and also that vectorization_predicate is
+// ignored.
 void test4(int *List, int Length) {
 // CHECK-LABEL: @{{.*}}test4{{.*}}(
 // CHECK: br label {{.*}}, !llvm.loop ![[LOOP4:.*]]
@@ -48,7 +48,7 @@ void test4(int *List, int Length) {
     List[i] = i * 2;
 }
 
-// Check that vectorize and vectorize_predicate are disabled.
+// Check that vectorize is disabled and vectorize_predicate is ignored.
 void test5(int *List, int Length) {
 // CHECK-LABEL: @{{.*}}test5{{.*}}(
 // CHECK: br label {{.*}}, !llvm.loop ![[LOOP5:.*]]
@@ -114,16 +114,16 @@ void test9(int *List, int Length) {
 // CHECK-NEXT: ![[LOOP3]] = distinct !{![[LOOP3]], [[MP]], [[GEN6]], [[GEN3]]}
 
 // CHECK-NEXT: ![[LOOP4]] = distinct !{![[LOOP4]], [[MP]], [[GEN10:![0-9]+]]}
-// CHECK-NEXT: [[GEN10]] = !{!"llvm.loop.vectorize.width", i32 1}
+// CHECK-NEXT: [[GEN10]] = !{!"llvm.loop.vectorize.enable", i1 false}
 
-// CHECK-NEXT: ![[LOOP5]] = distinct !{![[LOOP5]], [[MP]], [[GEN6]], [[GEN10]]}
+// CHECK-NEXT: ![[LOOP5]] = distinct !{![[LOOP5]], [[MP]], [[GEN10]]}
 
-// CHECK-NEXT: ![[LOOP6]] = distinct !{![[LOOP6]], [[MP]], [[GEN8]], [[GEN10]], [[GEN11:![0-9]+]]}
-// CHECK-NEXT: [[GEN11]] = !{!"llvm.loop.vectorize.scalable.enable", i1 false}
+// CHECK-NEXT: ![[LOOP6]] = distinct !{![[LOOP6]], [[MP]], [[GEN10]]}
 
-// CHECK-NEXT: ![[LOOP7]] = distinct !{![[LOOP7]], [[MP]], [[GEN8]], [[GEN12:![0-9]+]], [[GEN11]], [[GEN3]]}
-// CHECK-NEXT: [[GEN12]] = !{!"llvm.loop.vectorize.width", i32 4}
+// CHECK-NEXT: ![[LOOP7]] = distinct !{![[LOOP7]], [[MP]], [[GEN8]], [[GEN11:![0-9]+]], [[GEN12:![0-9]+]], [[GEN3]]}
+// CHECK-NEXT: [[GEN11]] = !{!"llvm.loop.vectorize.width", i32 4}
+// CHECK-NEXT: [[GEN12]] = !{!"llvm.loop.vectorize.scalable.enable", i1 false}
 
-// CHECK-NEXT: ![[LOOP8]] = distinct !{![[LOOP8]], [[MP]], [[GEN6]], [[GEN10]], [[GEN11]]}
+// CHECK-NEXT: ![[LOOP8]] = distinct !{![[LOOP8]], [[MP]], [[GEN10]]}
 
-// CHECK-NEXT: ![[LOOP9]] = distinct !{![[LOOP9]], [[MP]], [[GEN6]], [[GEN12]], [[GEN11]], [[GEN3]]}
+// CHECK-NEXT: ![[LOOP9]] = distinct !{![[LOOP9]], [[MP]], [[GEN6]], [[GEN11]], [[GEN12]], [[GEN3]]}

clang/test/CodeGenCXX/pragma-loop-safety.cpp

@@ -53,6 +53,6 @@ void interleave_test(int *List, int Length) {
 // CHECK: ![[INTERLEAVE_1]] = !{!"llvm.loop.interleave.count", i32 1}
 // CHECK: ![[INTENABLE_1]] = !{!"llvm.loop.vectorize.enable", i1 true}
 // CHECK: ![[ACCESS_GROUP_8]] = distinct !{}
-// CHECK: ![[LOOP2_HINTS]] = distinct !{![[LOOP2_HINTS]], [[MP]], ![[PARALLEL_ACCESSES_11:[0-9]+]], ![[UNROLL_DISABLE]], ![[WIDTH_1:[0-9]+]], ![[INTENABLE_1]]}
+// CHECK: ![[LOOP2_HINTS]] = distinct !{![[LOOP2_HINTS]], [[MP]], ![[PARALLEL_ACCESSES_11:[0-9]+]], ![[UNROLL_DISABLE]], ![[VECTORIZE_DISABLED:[0-9]+]]}
 // CHECK: ![[PARALLEL_ACCESSES_11]] = !{!"llvm.loop.parallel_accesses", ![[ACCESS_GROUP_8]]}
-// CHECK: ![[WIDTH_1]] = !{!"llvm.loop.vectorize.width", i32 1}
+// CHECK: ![[VECTORIZE_DISABLED]] = !{!"llvm.loop.vectorize.enable", i1 false}

clang/test/CodeGenCXX/pragma-loop.cpp

@@ -194,7 +194,7 @@ void for_test_scalable(int *List, int Length) {
   }
 }
 
-// Verify for loop is performing scalable vectorization
+// Verify for loop is NOT performing vectorization because the width is 1
 void for_test_scalable_1(int *List, int Length) {
 #pragma clang loop vectorize_width(1, scalable) interleave_count(4) unroll(disable) distribute(disable)
   for (int i = 0; i < Length; i++) {
@@ -203,6 +203,24 @@ void for_test_scalable_1(int *List, int Length) {
   }
 }
 
+// Verify for loop is performing scalable vectorization
+void for_test_scalable_2(int *List, int Length) {
+#pragma clang loop vectorize_width(2, scalable) interleave_count(4) unroll(disable) distribute(disable)
+  for (int i = 0; i < Length; i++) {
+    // CHECK: br label {{.*}}, !llvm.loop ![[LOOP_20:.*]]
+    List[i] = i * 2;
+  }
+}
+
+// Verify unroll attributes are directly attached to the loop metadata
+void for_test_vectorize_disable_unroll(int *List, int Length) {
+#pragma clang loop vectorize(disable) unroll_count(8)
+  for (int i = 0; i < Length; i++) {
+    // CHECK: br label {{.*}}, !llvm.loop ![[LOOP_21:.*]]
+    List[i] = i * 2;
+  }
+}
+
 // CHECK-DAG: ![[MP:[0-9]+]] = !{!"llvm.loop.mustprogress"}
 
 // CHECK-DAG: ![[UNROLL_DISABLE:[0-9]+]] = !{!"llvm.loop.unroll.disable"}
@@ -220,9 +238,9 @@ void for_test_scalable_1(int *List, int Length) {
 // CHECK-DAG: ![[INTERLEAVE_16:[0-9]+]] = !{!"llvm.loop.interleave.count", i32 16}
 
 // CHECK-DAG: ![[VECTORIZE_ENABLE:[0-9]+]] = !{!"llvm.loop.vectorize.enable", i1 true}
+// CHECK-DAG: ![[VECTORIZE_DISABLE:[0-9]+]] = !{!"llvm.loop.vectorize.enable", i1 false}
 // CHECK-DAG: ![[FIXED_VEC:[0-9]+]] = !{!"llvm.loop.vectorize.scalable.enable", i1 false}
 // CHECK-DAG: ![[SCALABLE_VEC:[0-9]+]] = !{!"llvm.loop.vectorize.scalable.enable", i1 true}
-// CHECK-DAG: ![[WIDTH_1:[0-9]+]] = !{!"llvm.loop.vectorize.width", i32 1}
 // CHECK-DAG: ![[WIDTH_2:[0-9]+]] = !{!"llvm.loop.vectorize.width", i32 2}
 // CHECK-DAG: ![[WIDTH_5:[0-9]+]] = !{!"llvm.loop.vectorize.width", i32 5}
 // CHECK-DAG: ![[WIDTH_6:[0-9]+]] = !{!"llvm.loop.vectorize.width", i32 6}
@@ -241,7 +259,7 @@ void for_test_scalable_1(int *List, int Length) {
 
 // CHECK-DAG: ![[LOOP_4]] = distinct !{![[LOOP_4]], ![[WIDTH_2]], ![[FIXED_VEC]], ![[INTERLEAVE_2]], ![[VECTORIZE_ENABLE]]}
 
-// CHECK-DAG: ![[LOOP_5]] = distinct !{![[LOOP_5]], ![[MP]], ![[UNROLL_DISABLE]], ![[DISTRIBUTE_DISABLE]], ![[WIDTH_1]]}
+// CHECK-DAG: ![[LOOP_5]] = distinct !{![[LOOP_5]], ![[MP]], ![[UNROLL_DISABLE]], ![[DISTRIBUTE_DISABLE]], ![[VECTORIZE_DISABLE]]}
 
 // CHECK-DAG: ![[LOOP_6]] = distinct !{![[LOOP_6]], ![[MP]], ![[WIDTH_2]], ![[FIXED_VEC]], ![[INTERLEAVE_2]], ![[VECTORIZE_ENABLE]], ![[FOLLOWUP_VECTOR_3]]}
 
@@ -269,4 +287,7 @@ void for_test_scalable_1(int *List, int Length) {
 
 // CHECK-DAG: ![[LOOP_17]] = distinct !{![[LOOP_17]], ![[MP]], ![[UNROLL_DISABLE]], ![[DISTRIBUTE_DISABLE]], ![[FIXED_VEC]], ![[INTERLEAVE_4]], ![[VECTORIZE_ENABLE]]}
 // CHECK-DAG: ![[LOOP_18]] = distinct !{![[LOOP_18]], ![[MP]], ![[UNROLL_DISABLE]], ![[DISTRIBUTE_DISABLE]], ![[SCALABLE_VEC]], ![[INTERLEAVE_4]], ![[VECTORIZE_ENABLE]]}
-// CHECK-DAG: ![[LOOP_19]] = distinct !{![[LOOP_19]], ![[MP]], ![[UNROLL_DISABLE]], ![[DISTRIBUTE_DISABLE]], ![[WIDTH_1]], ![[SCALABLE_VEC]], ![[INTERLEAVE_4]], ![[VECTORIZE_ENABLE]]}
+// CHECK-DAG: ![[LOOP_19]] = distinct !{![[LOOP_19]], ![[MP]], ![[UNROLL_DISABLE]], ![[DISTRIBUTE_DISABLE]], ![[VECTORIZE_DISABLE]]}
+// CHECK-DAG: ![[LOOP_20]] = distinct !{![[LOOP_20]], ![[MP]], ![[UNROLL_DISABLE]], ![[DISTRIBUTE_DISABLE]], ![[WIDTH_2]], ![[SCALABLE_VEC]], ![[INTERLEAVE_4]], ![[VECTORIZE_ENABLE]]}
+
+// CHECK-DAG: ![[LOOP_21]] = distinct !{![[LOOP_21]], ![[MP]], ![[VECTORIZE_DISABLE]], ![[UNROLL_8]]}