[SVE] Add codegen support for vscale_range() function attribute

This commit adds support for the `vscale_range()` LLVM function attribute to be generated for SVE and SME targets.
Some LLVM optimisation passes make use of the `vscale_range()` function attribute when scalable vectors are present (e.g. BasicAA llvm/llvm-project/pull/80445), so we include it alongside the "target_cpu" and "target-features" attributes.

Author: Anndrey24

src/target/llvm/codegen_llvm.cc

@@ -104,6 +104,7 @@
 #include <vector>
 
 #include "../../arith/pattern_match.h"
+#include "../../arith/scalable_expression.h"
 #include "../build_common.h"
 #include "../func_registry_generator.h"
 #include "codegen_params.h"
@@ -1127,6 +1128,13 @@ void CodeGenLLVM::SetTargetAttributes(llvm::Function* func) {
   if (!features.empty()) {
     func->addFnAttr("target-features", features);
   }
+#if TVM_LLVM_VERSION >= 130
+  // Add vscale_range() function attribute when appropriate.
+  if (llvm_target_->TargetHasCPUFeature("sve") || llvm_target_->TargetHasCPUFeature("sme")) {
+    func->addFnAttr(llvm::Attribute::getWithVScaleRangeArgs(
+        *llvm_target_->GetContext(), 1, tvm::arith::kAArch64VScaleValues.size()));
+  }
+#endif
 }
 
 void CodeGenLLVM::EmitFloat16ConversionBuiltins(bool use_float16_abi) {

src/target/llvm/codegen_llvm.h

@@ -427,7 +427,7 @@ class CodeGenLLVM : public ExprFunctor<llvm::Value*(const PrimExpr&)>,
                                    llvm::ArrayRef<llvm::Type*> arg_types);
   /*!
    * \brief Set target-related attributes on the LLVM function \p func. This
-   *        includes "target-cpu" and "target-features" if present.
+   *        includes "target-cpu", "target-features" and "vscale_range()" if present.
    *
    * \param func The function to set attributes on.
    */

tests/python/codegen/test_target_codegen_aarch64.py

@@ -537,6 +537,44 @@ def my_func(a: T.handle):
     assert re.findall(r" store <vscale x 4 x float>", llvm), "No scalable store in generated LLVM."
 
 
+@pytest.mark.skipif(
+    llvm_version_major() < 13,
+    reason="Function attribute vscale_range() is not supported in earlier versions of LLVM",
+)
+@pytest.mark.parametrize(
+    "mattr,expect_attr",
+    [
+        ("+neon", False),
+        ("+sve", True),
+        ("+v9a", True),
+        ("+sme", True),
+    ],
+)
+def test_vscale_range_function_attribute(mattr, expect_attr):
+    target = f"llvm -mtriple=aarch64-linux-gnu -mattr={mattr}"
+
+    m = te.var("m")
+    A = te.placeholder(m, dtype="float32", name="A")
+    C = te.compute((m), lambda i: A[i] + 1, name="C")
+    s = te.create_schedule([C.op])
+
+    with tvm.target.Target(target) as target:
+        f = tvm.build(s, [A, C], target)
+
+    # Check if the vscale_range() attribute exists
+    ll = f.get_source("ll")
+    attr = re.findall(rf".*vscale_range\(\d+,\d+\)*.", ll)
+
+    if expect_attr:
+        assert (
+            len(attr) > 0
+        ), f"Function attribute vscale_range() was not found in generated LLVM IR"
+    else:
+        assert (
+            len(attr) == 0
+        ), f"Unexpected function attribute vscale_range() was found in generated LLVM IR"
+
+
 @pytest.mark.skipif(
     llvm_version_major() < 16, reason="Test requires an LLVM version of at least 16 to target SME"
 )