[VFABI] Add LLVM internal mangling for vector functions.

Summary:
This patch adds a custom ISA for vector functions for internal use
in LLVM. The <isa> token is set to "_LLVM_", and it is not attached
to any specific instruction Vector ISA, or Vector Function ABI.

The ISA is used as a token for handling Vector Function ABI-style
vectorization for those vector functions that are not directly
associated to any existing Vector Function ABI (for example, some of
the vector functions exposed by TargetLibraryInfo). The demangling
function for this ISA in a Vector Function ABI context is set to be
the same as the common one shared between X86 and AArch64.

Reviewers: jdoerfert, sdesmalen, simoll

Subscribers: kristof.beyls, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70089

3 files changed, 39 insertions, 10 deletions

diff --git a/llvm/include/llvm/Analysis/VectorUtils.h b/llvm/include/llvm/Analysis/VectorUtils.h
index 850bc10f037..e9c96cc96cb 100644
--- a/llvm/include/llvm/Analysis/VectorUtils.h
+++ b/llvm/include/llvm/Analysis/VectorUtils.h
@@ -48,7 +48,9 @@ enum class VFISAKind {
   AVX,          // x86 AVX
   AVX2,         // x86 AVX2
   AVX512,       // x86 AVX512
-  Unknown       // Unknown ISA
+  LLVM,         // LLVM internal ISA for functions that are not
+  // attached to an existing ABI via name mangling.
+  Unknown // Unknown ISA
 };
 
 /// Encapsulates information needed to describe a parameter.
@@ -103,6 +105,9 @@ struct VFInfo {
 };
 
 namespace VFABI {
+/// LLVM Internal VFABI ISA token for vector functions.
+static constexpr char const *_LLVM_ = "_LLVM_";
+
 /// Function to contruct a VFInfo out of a mangled names in the
 /// following format:
 ///
diff --git a/llvm/lib/Analysis/VFABIDemangling.cpp b/llvm/lib/Analysis/VFABIDemangling.cpp
index 152f7ae4667..067283d38b6 100644
--- a/llvm/lib/Analysis/VFABIDemangling.cpp
+++ b/llvm/lib/Analysis/VFABIDemangling.cpp
@@ -28,15 +28,20 @@ ParseRet tryParseISA(StringRef &MangledName, VFISAKind &ISA) {
   if (MangledName.empty())
     return ParseRet::Error;
 
-  ISA = StringSwitch<VFISAKind>(MangledName.take_front(1))
-            .Case("n", VFISAKind::AdvancedSIMD)
-            .Case("s", VFISAKind::SVE)
-            .Case("b", VFISAKind::SSE)
-            .Case("c", VFISAKind::AVX)
-            .Case("d", VFISAKind::AVX2)
-            .Case("e", VFISAKind::AVX512)
-            .Default(VFISAKind::Unknown);
-  MangledName = MangledName.drop_front(1);
+  if (MangledName.startswith(VFABI::_LLVM_)) {
+    MangledName = MangledName.drop_front(strlen(VFABI::_LLVM_));
+    ISA = VFISAKind::LLVM;
+  } else {
+    ISA = StringSwitch<VFISAKind>(MangledName.take_front(1))
+              .Case("n", VFISAKind::AdvancedSIMD)
+              .Case("s", VFISAKind::SVE)
+              .Case("b", VFISAKind::SSE)
+              .Case("c", VFISAKind::AVX)
+              .Case("d", VFISAKind::AVX2)
+              .Case("e", VFISAKind::AVX512)
+              .Default(VFISAKind::Unknown);
+    MangledName = MangledName.drop_front(1);
+  }
 
   return ParseRet::OK;
 }
@@ -287,6 +292,7 @@ ParseRet tryParseAlign(StringRef &ParseString, Align &Alignment) {
 // Format of the ABI name:
 // _ZGV<isa><mask><vlen><parameters>_<scalarname>[(<redirection>)]
 Optional<VFInfo> VFABI::tryDemangleForVFABI(StringRef MangledName) {
+  const StringRef OriginalName = MangledName;
   // Assume there is no custom name <redirection>, and therefore the
   // vector name consists of
   // _ZGV<isa><mask><vlen><parameters>_<scalarname>.
@@ -370,6 +376,11 @@ Optional<VFInfo> VFABI::tryDemangleForVFABI(StringRef MangledName) {
       return None;
   }
 
+  // LLVM internal mapping via the TargetLibraryInfo (TLI) must be
+  // redirected to an existing name.
+  if (ISA == VFISAKind::LLVM && VectorName == OriginalName)
+    return None;
+
   // When <mask> is "M", we need to add a parameter that is used as
   // global predicate for the function.
   if (IsMasked) {
diff --git a/llvm/unittests/Analysis/VectorFunctionABITest.cpp b/llvm/unittests/Analysis/VectorFunctionABITest.cpp
index 331f46b39b3..6fe85298d54 100644
--- a/llvm/unittests/Analysis/VectorFunctionABITest.cpp
+++ b/llvm/unittests/Analysis/VectorFunctionABITest.cpp
@@ -346,6 +346,13 @@ TEST_F(VFABIParserTest, ISAIndependentMangling) {
   __COMMON_CHECKS;
   EXPECT_EQ(VectorName, "_ZGVeN2vls2Ls27Us4Rs5l1L10U100R1000u2_sin");
 
+  // LLVM: <isa> = "_LLVM_" internal vector function.
+  EXPECT_TRUE(
+      invokeParser("_ZGV_LLVM_N2vls2Ls27Us4Rs5l1L10U100R1000u2_sin(vectorf)"));
+  EXPECT_EQ(ISA, VFISAKind::LLVM);
+  __COMMON_CHECKS;
+  EXPECT_EQ(VectorName, "vectorf");
+
   // Unknown ISA (randomly using "q"). This test will need update if
   // some targets decide to use "q" as their ISA token.
   EXPECT_TRUE(invokeParser("_ZGVqN2vls2Ls27Us4Rs5l1L10U100R1000u2_sin"));
@@ -473,3 +480,9 @@ TEST_F(VFABIAttrTest, Read) {
   Exp.push_back("_ZGVnN4v_g");
   EXPECT_EQ(Mappings, Exp);
 }
+
+TEST_F(VFABIParserTest, LLVM_InternalISA) {
+  EXPECT_FALSE(invokeParser("_ZGV_LLVM_N2v_sin"));
+  EXPECT_TRUE(invokeParser("_ZGV_LLVM_N2v_sin_(vector_name)"));
+  EXPECT_EQ(ISA, VFISAKind::LLVM);
+}