[VFABI] Read/Write functions for the VFABI attribute.

The attribute is stored at the `FunctionIndex` attribute set, with the
name "vector-function-abi-variant".

The get/set methods of the attribute have assertion to verify that:

1. Each name in the attribute is a valid VFABI mangled name.

2. Each name in the attribute correspond to a function declared in the
   module.

Differential Revision: https://reviews.llvm.org/D69976

llvm/include/llvm/Analysis/VectorUtils.h

@@ -14,6 +14,7 @@
 #define LLVM_ANALYSIS_VECTORUTILS_H
 
 #include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/Analysis/LoopAccessAnalysis.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/Support/CheckedArithmetic.h"
@@ -121,14 +122,20 @@ namespace VFABI {
 /// * x86 (libmvec): https://sourceware.org/glibc/wiki/libmvec and
 ///  https://sourceware.org/glibc/wiki/libmvec?action=AttachFile&do=view&target=VectorABI.txt
 ///
-///
-///
 /// \param MangledName -> input string in the format
 /// _ZGV<isa><mask><vlen><parameters>_<scalarname>[(<redirection>)].
 Optional<VFInfo> tryDemangleForVFABI(StringRef MangledName);
 
 /// Retrieve the `VFParamKind` from a string token.
 VFParamKind getVFParamKindFromString(const StringRef Token);
+
+// Name of the attribute where the variant mappings are stored.
+static constexpr char const *MappingsAttrName = "vector-function-abi-variant";
+
+/// Populates a set of strings representing the Vector Function ABI variants
+/// associated to the CallInst CI.
+void getVectorVariantNames(const CallInst &CI,
+                           SmallVectorImpl<std::string> &VariantMappings);
 } // end namespace VFABI
 
 template <typename T> class ArrayRef;
@@ -137,7 +144,6 @@ class GetElementPtrInst;
 template <typename InstTy> class InterleaveGroup;
 class Loop;
 class ScalarEvolution;
-class TargetLibraryInfo;
 class TargetTransformInfo;
 class Type;
 class Value;

llvm/include/llvm/Transforms/Utils/ModuleUtils.h

@@ -13,6 +13,7 @@
 #ifndef LLVM_TRANSFORMS_UTILS_MODULEUTILS_H
 #define LLVM_TRANSFORMS_UTILS_MODULEUTILS_H
 
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringRef.h"
 #include <utility> // for std::pair
 
@@ -108,6 +109,23 @@ void filterDeadComdatFunctions(
 /// unique identifier for this module, so we return the empty string.
 std::string getUniqueModuleId(Module *M);
 
+class TargetLibraryInfo;
+class CallInst;
+namespace VFABI {
+
+/// \defgroup Vector Function ABI (VABI) Module functions.
+///
+/// Utility functions for VFABI data that can modify the module.
+///
+/// @{
+/// Overwrite the Vector Function ABI variants attribute with the names provide
+/// in \p VariantMappings.
+void setVectorVariantNames(CallInst *CI,
+                           const SmallVector<std::string, 8> &VariantMappings);
+
+/// @}
+} // End VFABI namespace
+
 } // End llvm namespace
 
 #endif //  LLVM_TRANSFORMS_UTILS_MODULEUTILS_H

llvm/lib/Analysis/VFABIDemangling.cpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallString.h"
 #include "llvm/Analysis/VectorUtils.h"
 
 using namespace llvm;
@@ -34,7 +36,6 @@ ParseRet tryParseISA(StringRef &MangledName, VFISAKind &ISA) {
             .Case("d", VFISAKind::AVX2)
             .Case("e", VFISAKind::AVX512)
             .Default(VFISAKind::Unknown);
-
   MangledName = MangledName.drop_front(1);
 
   return ParseRet::OK;
@@ -338,7 +339,7 @@ Optional<VFInfo> VFABI::tryDemangleForVFABI(StringRef MangledName) {
     }
   } while (ParamFound == ParseRet::OK);
 
-  // A valid MangledName mus have at least one valid entry in the
+  // A valid MangledName must have at least one valid entry in the
   // <parameters>.
   if (Parameters.empty())
     return None;

llvm/lib/Analysis/VectorUtils.cpp

@@ -1159,3 +1159,22 @@ void InterleaveGroup<Instruction>::addMetadata(Instruction *NewInst) const {
   propagateMetadata(NewInst, VL);
 }
 }
+
+void VFABI::getVectorVariantNames(
+    const CallInst &CI, SmallVectorImpl<std::string> &VariantMappings) {
+  const StringRef S =
+      CI.getAttribute(AttributeList::FunctionIndex, VFABI::MappingsAttrName)
+          .getValueAsString();
+  SmallVector<StringRef, 8> ListAttr;
+  S.split(ListAttr, ",");
+
+  for (auto &S : SetVector<StringRef>(ListAttr.begin(), ListAttr.end())) {
+#ifndef NDEBUG
+    Optional<VFInfo> Info = VFABI::tryDemangleForVFABI(S);
+    assert(Info.hasValue() && "Invalid name for a VFABI variant.");
+    assert(CI.getModule()->getFunction(Info.getValue().VectorName) &&
+           "Vector function is missing.");
+#endif
+    VariantMappings.push_back(S);
+  }
+}

llvm/lib/Transforms/Utils/ModuleUtils.cpp

@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Utils/ModuleUtils.h"
+#include "llvm/Analysis/VectorUtils.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/IRBuilder.h"
@@ -280,3 +281,31 @@ std::string llvm::getUniqueModuleId(Module *M) {
   MD5::stringifyResult(R, Str);
   return ("$" + Str).str();
 }
+
+void VFABI::setVectorVariantNames(
+    CallInst *CI, const SmallVector<std::string, 8> &VariantMappings) {
+  if (VariantMappings.empty())
+    return;
+
+  SmallString<256> Buffer;
+  llvm::raw_svector_ostream Out(Buffer);
+  for (const std::string &VariantMapping : VariantMappings)
+    Out << VariantMapping << ",";
+  // Get rid of the trailing ','.
+  assert(!Buffer.str().empty() && "Must have at least one char.");
+  Buffer.pop_back();
+
+  Module *M = CI->getModule();
+#ifndef NDEBUG
+  for (const std::string &VariantMapping : VariantMappings) {
+    Optional<VFInfo> VI = VFABI::tryDemangleForVFABI(VariantMapping);
+    assert(VI.hasValue() && "Canno add an invalid VFABI name.");
+    assert(M->getNamedValue(VI.getValue().VectorName) &&
+           "Cannot add variant to attribute: "
+           "vector function declaration is missing.");
+  }
+#endif
+  CI->addAttribute(
+      AttributeList::FunctionIndex,
+      Attribute::get(M->getContext(), MappingsAttrName, Buffer.str()));
+}

llvm/unittests/Analysis/VectorFunctionABITest.cpp

@@ -7,6 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/VectorUtils.h"
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/IR/InstIterator.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -437,3 +439,37 @@ TEST_F(VFABIParserTest, ParseMaskingAVX512) {
   EXPECT_EQ(Parameters[1], VFParameter({1, VFParamKind::GlobalPredicate}));
   EXPECT_EQ(ScalarName, "sin");
 }
+
+class VFABIAttrTest : public testing::Test {
+protected:
+  void SetUp() override {
+    M = parseAssemblyString(IR, Err, Ctx);
+    // Get the only call instruction in the block, which is the first
+    // instruction.
+    CI = dyn_cast<CallInst>(&*(instructions(M->getFunction("f")).begin()));
+  }
+  const char *IR = "define i32 @f(i32 %a) {\n"
+                   " %1 = call i32 @g(i32 %a) #0\n"
+                   "  ret i32 %1\n"
+                   "}\n"
+                   "declare i32 @g(i32)\n"
+                   "declare <2 x i32> @custom_vg(<2 x i32>)"
+                   "declare <4 x i32> @_ZGVnN4v_g(<4 x i32>)"
+                   "declare <8 x i32> @_ZGVnN8v_g(<8 x i32>)"
+                   "attributes #0 = { "
+                   "\"vector-function-abi-variant\"=\""
+                   "_ZGVnN2v_g(custom_vg),_ZGVnN4v_g\" }";
+  LLVMContext Ctx;
+  SMDiagnostic Err;
+  std::unique_ptr<Module> M;
+  CallInst *CI;
+  SmallVector<std::string, 8> Mappings;
+};
+
+TEST_F(VFABIAttrTest, Read) {
+  VFABI::getVectorVariantNames(*CI, Mappings);
+  SmallVector<std::string, 8> Exp;
+  Exp.push_back("_ZGVnN2v_g(custom_vg)");
+  Exp.push_back("_ZGVnN4v_g");
+  EXPECT_EQ(Mappings, Exp);
+}

llvm/unittests/Transforms/Utils/CMakeLists.txt

@@ -18,4 +18,5 @@ add_llvm_unittest(UtilsTests
   SSAUpdaterBulkTest.cpp
   UnrollLoopTest.cpp
   ValueMapperTest.cpp
+  VFABIUtils.cpp
   )

llvm/unittests/Transforms/Utils/VFABIUtils.cpp

@@ -0,0 +1,55 @@
+//===------- VFABIUtils.cpp - VFABI Unittests  ----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/IR/InstIterator.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+class VFABIAttrTest : public testing::Test {
+protected:
+  void SetUp() override {
+    M = parseAssemblyString(IR, Err, Ctx);
+    // Get the only call instruction in the block, which is the first
+    // instruction.
+    CI = dyn_cast<CallInst>(&*(instructions(M->getFunction("f")).begin()));
+  }
+  const char *IR = "define i32 @f(i32 %a) {\n"
+                   " %1 = call i32 @g(i32 %a) #0\n"
+                   "  ret i32 %1\n"
+                   "}\n"
+                   "declare i32 @g(i32)\n"
+                   "declare <2 x i32> @custom_vg(<2 x i32>)"
+                   "declare <4 x i32> @_ZGVnN4v_g(<4 x i32>)"
+                   "declare <8 x i32> @_ZGVnN8v_g(<8 x i32>)"
+                   "attributes #0 = { "
+                   "\"vector-function-abi-variant\"=\""
+                   "_ZGVnN2v_g(custom_vg),_ZGVnN4v_g\" }";
+  LLVMContext Ctx;
+  SMDiagnostic Err;
+  std::unique_ptr<Module> M;
+  CallInst *CI;
+  SmallVector<std::string, 8> Mappings;
+};
+
+TEST_F(VFABIAttrTest, Write) {
+  Mappings.push_back("_ZGVnN8v_g");
+  Mappings.push_back("_ZGVnN2v_g(custom_vg)");
+  VFABI::setVectorVariantNames(CI, Mappings);
+  const AttributeList Attrs = CI->getAttributes();
+  const AttributeSet FnAttrs = Attrs.getFnAttributes();
+  const StringRef S = CI->getAttribute(AttributeList::FunctionIndex,
+                                       "vector-function-abi-variant")
+                          .getValueAsString();
+  EXPECT_EQ(S, "_ZGVnN8v_g,_ZGVnN2v_g(custom_vg)");
+}