[mlir] Generalize intrinsic builders in the LLVM dialect definition

[ftynse]

Summary

All LLVM IR intrinsics are constructed in a similar way. The ODS definition of
the LLVM dialect in MLIR also lists multiple intrinsics, many of which
reproduce the same (or similar enough) code stanza to translate the MLIR
operation into the LLVM IR intrinsic. Provide a single base class containing
parameterizable code to build LLVM IR intrinsics given their name and the lists
of overloadable operands and results. Use this class to remove (almost)
duplicate translations for intrinsics defined in LLVMOps.td.

[aartbik]

I like where this is going a lot. Some suggestions on the doc though

mlir/include/mlir/Dialect/LLVMIR/LLVMOpBase.td

78

If this is deprecated, add a TODO on the plan on the path forward (e.g. remove when ....)

125

typo: operation

140

in *the* LLVM sense

167

since this (and L157) is the class doc most people will read (and not the doc of the implementation oriented base class), some more doc on sample use would be useful.

E.g.
sample use:

LLVM_OneResultIntrOp<"name",  [0], [1], []>,   Arguments<(ins LLVM_Type, LLVM_Type)>;

means
....

[ftynse]

Address review

mlir/include/mlir/Dialect/LLVMIR/LLVMOpBase.td

78

After all, I'll update this and all users in the next commit.

[nicolasvasilache]

LG!

[shraiysh]

Hi, I was trying to implement some llvm intrinsics and wanted to understand the purpose of overloaded operands. The LLVM reference manual does not say that prefetch is overloaded.

mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td

719

Can you please clarify why [0] is added to prefetch?

mlir/include/mlir/Dialect/LLVMIR/LLVMOpBase.td

 
 // Base class for LLVM operations. All operations get an "llvm." prefix in
 // their name automatically. LLVM operations have either zero or one result,
 // this class is specialized below for both cases and should not be used
 // directly.
 class LLVM_Op<string mnemonic, list<OpTrait> traits = []> :
     LLVM_OpBase<LLVM_Dialect, mnemonic, traits>;
 
-// Base class for LLVM intrinsics operation. It is the same as an LLVM_Op
-// but the operation has a ".intr." element in the prefix becoming
-// "llvm.intr.*".
+// Compatibility class for LLVM intrinsic operations.
 class LLVM_IntrOp<string mnemonic, list<OpTrait> traits = []> :
     LLVM_Op<"intr."#mnemonic, traits>;
 
 // Case of the LLVM enum attribute backed by I64Attr with customized string
 // representation that corresponds to what is visible in the textual IR form.
 // The parameters are as follows:
 //   - `cppSym`: name of the C++ enumerant for this case in MLIR API;
 //   - `irSym`: keyword used in the custom form of MLIR operation;

 class LLVM_EnumAttr<string name, string llvmName, string description,
                     list<LLVM_EnumAttrCase> cases> :
     I64EnumAttr<name, description, cases> {
 
   // The equivalent enum class name in LLVM.
   string llvmClassName = llvmName;
 }
 
-// LLVM vector reduction over a single vector.
-class LLVM_VectorReduction<string mnem> :
-  LLVM_IntrOp<"experimental.vector.reduce." # mnem, []>,
-  Arguments<(ins LLVM_Type)>, Results<(outs LLVM_Type:$res)> {
-    let llvmBuilder = [{
-      llvm::Module *module = builder.GetInsertBlock()->getModule();
-      llvm::Function *fn = llvm::Intrinsic::getDeclaration(
-        module,
-        llvm::Intrinsic::experimental_vector_reduce_}] #
-        !subst(".","_", mnem) # [{, {
-          opInst.getOperand(0).getType().cast<LLVM::LLVMType>()
-          .getUnderlyingType(),
-        });
-      auto operands = lookupValues(opInst.getOperands());
-      $res = builder.CreateCall(fn, operands);
-    }];
+// For every value in the list, substitutes the value in the place of "$0" in
+// "pattern" and stores the list of strings as "lst".
+class ListIntSubst<string pattern, list<int> values> {
+  list<string> lst = !foreach(x, values,
+                              !subst("$0", !cast<string>(x), pattern));
+}
+
+// Patterns with code obtaining the LLVM IR type of the given operand or result
+// of operation. "$0" is expected to be replaced by the position of the operand
+// or result in the operation.
+def LLVM_IntrPatterns {
+  string operand =
+    [{opInst.getOperand($0).getType()
+      .cast<LLVM::LLVMType>().getUnderlyingType()}];
+  string result =
+    [{opInst.getResult($0).getType()
+      .cast<LLVM::LLVMType>().getUnderlyingType()}];
 }
 
-// LLVM vector reduction over a single vector, with an initial value.
-class LLVM_VectorReductionV2<string mnem> :
-  LLVM_IntrOp<"experimental.vector.reduce.v2." # mnem, []>,
-  Arguments<(ins LLVM_Type, LLVM_Type)>, Results<(outs LLVM_Type:$res)> {
-    let llvmBuilder = [{
-      llvm::Module *module = builder.GetInsertBlock()->getModule();
-      llvm::Function *fn = llvm::Intrinsic::getDeclaration(
+
+// Base class for LLVM intrinsics operation. It is similar to LLVM_Op, but
+// provides the "llvmBuilder" field for constructing the intrinsic. The builder
+// relies on the contents on "overloadedResults" and "overloadedOperands" lists
+// that contain the positions of intrinsic results and operands that are
+// overloadable in the LLVM sense, that is their types must be passed in during
+// the construction of the intrinsic declaration to differentiate between
+// differently-typed versions of the intrinsic. "opName" contains the name of
+// the operation to be associated with the intrinsic and "enumName" contains the
+// name of the intrinsic as appears in `llvm::Intrinsic` enum; one usually wants
+// these to be related.
+class LLVM_IntrOpBase<Dialect dialect, string opName, string enumName,
+                      list<int> overloadedResults, list<int> overloadedOperands,
+                      list<OpTrait> traits, bit hasResult>
+    : LLVM_OpBase<dialect, opName, traits>,
+      Results<!if(hasResult, (outs LLVM_Type:$res), (outs))> {
         module,
-        llvm::Intrinsic::experimental_vector_reduce_v2_}] #
-        !subst(".","_", mnem) # [{, {
-          opInst.getResult(0).getType().cast<LLVM::LLVMType>()
-          .getUnderlyingType(),
-          opInst.getOperand(1).getType().cast<LLVM::LLVMType>()
-          .getUnderlyingType(),
+        llvm::Intrinsic::}] # enumName # [{,
+        { }] # StrJoin<!listconcat(
+            ListIntSubst<LLVM_IntrPatterns.result, overloadedResults>.lst,
+            ListIntSubst<LLVM_IntrPatterns.operand,
+                         overloadedOperands>.lst)>.result # [{
         });
-      auto operands = lookupValues(opInst.getOperands());
-      $res = builder.CreateCall(fn, operands);
-    }];
+    }] # !if(hasResult, "$res = ", "") # [{builder.CreateCall(fn, operands);
 }
 
+// Base class for LLVM intrinsic operations returning no results. Places the
+// intrinsic into the LLVM dialect and prefixes its name with "intr.".
+//
+// Sample use: derive an entry from this class and populate the fields.
+//
+//    def LLVM_Name : LLVM_ZeroResultIntrOp<"name", [0], [NoSideEffect]>,
+//                    Arguments<(ins LLVM_Type, LLVM_Type)>;
+//
+// The mnemonic will be prefixed with "llvm.intr.", where the "llvm." part comes
+// from the LLVM dialect. The overloadedOperands list contains the indices of
+// the operands the type of which will be passed in the LLVM IR intrinsic
+// builder. In the example above, the Op has two arguments, but only the first
+// one (as indicated by `[0]`) is necessary to resolve the overloaded intrinsic.
+// The Op has no results.
+class LLVM_ZeroResultIntrOp<string mnem, list<int> overloadedOperands = [],
+                            list<OpTrait> traits = []>
+    : LLVM_IntrOpBase<LLVM_Dialect, "intr." # mnem, !subst(".", "_", mnem),
+                      [], overloadedOperands, traits, 0>;
+
+// Base class for LLVM intrinsic operations returning one result. Places the
+// intrinsic into the LLVM dialect and prefixes its name with "intr.". This is
+// similar to LLVM_ZeroResultIntrOp but allows one to define Ops returning one
+// result, called "res". Additionally, the overloadedResults list should contain
+// "0" if the result must be used to resolve overloaded intrinsics, or remain
+// empty otherwise.
+class LLVM_OneResultIntrOp<string mnem, list<int> overloadedResults = [],
+                           list<int> overloadedOperands = [],
+                           list<OpTrait> traits = []>
+    : LLVM_IntrOpBase<LLVM_Dialect, "intr." # mnem, !subst(".", "_", mnem),
+                      overloadedResults, overloadedOperands, traits, 1>;
+
+// LLVM vector reduction over a single vector.
+class LLVM_VectorReduction<string mnem>
+    : LLVM_OneResultIntrOp<"experimental.vector.reduce." # mnem, [], [0], []>,
+      Arguments<(ins LLVM_Type)>;
+
+// LLVM vector reduction over a single vector, with an initial value.
+class LLVM_VectorReductionV2<string mnem>
+    : LLVM_OneResultIntrOp<"experimental.vector.reduce.v2." # mnem,
+                           [0], [1], []>,
+      Arguments<(ins LLVM_Type, LLVM_Type)>;
+
 #endif  // LLVMIR_OP_BASE

mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td

 }
 
 // Operations that correspond to LLVM intrinsics. With MLIR operation set being
 // extendable, there is no reason to introduce a hard boundary between "core"
 // operations and intrinsics. However, we systematically prefix them with
 // "intr." to avoid potential name clashes.
 
 class LLVM_UnaryIntrinsicOp<string func, list<OpTrait> traits = []> :
-    LLVM_OneResultOp<"intr." # func,
+    LLVM_OneResultIntrOp<func, [], [0],
            !listconcat([NoSideEffect, SameOperandsAndResultType], traits)>,
-    Arguments<(ins LLVM_Type:$in)>,
-    LLVM_Builder<"$res = builder.CreateCall(llvm::Intrinsic::getDeclaration("
-      "builder.GetInsertBlock()->getModule(), llvm::Intrinsic::" # func # ","
-      "{$in->getType()}), {$in});"> {
-}
+    Arguments<(ins LLVM_Type:$in)>;
 
 class LLVM_BinarySameArgsIntrinsicOp<string func, list<OpTrait> traits = []> :
-    LLVM_OneResultOp<"intr." # func,
+    LLVM_OneResultIntrOp<func, [], [0],
            !listconcat([NoSideEffect, SameOperandsAndResultType], traits)>,
-    Arguments<(ins LLVM_Type:$a, LLVM_Type:$b)>,
-    LLVM_Builder<"$res = builder.CreateCall(llvm::Intrinsic::getDeclaration("
-      "builder.GetInsertBlock()->getModule(), llvm::Intrinsic::" # func # ","
-      "{$a->getType()}), {$a, $b});"> {
-}
+    Arguments<(ins LLVM_Type:$a, LLVM_Type:$b)>;
 
 class LLVM_TernarySameArgsIntrinsicOp<string func, list<OpTrait> traits = []> :
-    LLVM_OneResultOp<"intr." # func,
+    LLVM_OneResultIntrOp<func, [], [0],
            !listconcat([NoSideEffect, SameOperandsAndResultType], traits)>,
-    Arguments<(ins LLVM_Type:$a, LLVM_Type:$b, LLVM_Type:$c)>,
-    LLVM_Builder<"$res = builder.CreateCall(llvm::Intrinsic::getDeclaration("
-      "builder.GetInsertBlock()->getModule(), llvm::Intrinsic::" # func # ","
-      "{$a->getType()}), {$a, $b, $c});"> {
-}
+    Arguments<(ins LLVM_Type:$a, LLVM_Type:$b, LLVM_Type:$c)>;
 
+def LLVM_CopySignOp : LLVM_BinarySameArgsIntrinsicOp<"copysign">;
+def LLVM_CosOp : LLVM_UnaryIntrinsicOp<"cos">;
 def LLVM_ExpOp : LLVM_UnaryIntrinsicOp<"exp">;
 def LLVM_FAbsOp : LLVM_UnaryIntrinsicOp<"fabs">;
 def LLVM_FCeilOp : LLVM_UnaryIntrinsicOp<"ceil">;
-def LLVM_CosOp : LLVM_UnaryIntrinsicOp<"cos">;
-def LLVM_CopySignOp : LLVM_BinarySameArgsIntrinsicOp<"copysign">;
 def LLVM_FMAOp : LLVM_TernarySameArgsIntrinsicOp<"fma">;
 def LLVM_FMulAddOp : LLVM_TernarySameArgsIntrinsicOp<"fmuladd">;
-def LLVM_SqrtOp : LLVM_UnaryIntrinsicOp<"sqrt">;
-
-def LLVM_LogOp : LLVM_Op<"intr.log", [NoSideEffect]>,
-                   Arguments<(ins LLVM_Type:$in)>,
-                   Results<(outs LLVM_Type:$res)> {
-  let llvmBuilder = [{
-    llvm::Module *module = builder.GetInsertBlock()->getModule();
-    llvm::Function *fn = llvm::Intrinsic::getDeclaration(
-        module, llvm::Intrinsic::log, {$in->getType()});
-    $res = builder.CreateCall(fn, {$in});
-  }];
-}
-
-def LLVM_Log10Op : LLVM_Op<"intr.log10", [NoSideEffect]>,
-                   Arguments<(ins LLVM_Type:$in)>,
-                   Results<(outs LLVM_Type:$res)> {
-  let llvmBuilder = [{
-    llvm::Module *module = builder.GetInsertBlock()->getModule();
-    llvm::Function *fn = llvm::Intrinsic::getDeclaration(
-        module, llvm::Intrinsic::log10, {$in->getType()});
-    $res = builder.CreateCall(fn, {$in});
-  }];
-}
-
-def LLVM_Log2Op : LLVM_Op<"intr.log2", [NoSideEffect]>,
-                   Arguments<(ins LLVM_Type:$in)>,
-                   Results<(outs LLVM_Type:$res)> {
-  let llvmBuilder = [{
-    llvm::Module *module = builder.GetInsertBlock()->getModule();
-    llvm::Function *fn = llvm::Intrinsic::getDeclaration(
-        module, llvm::Intrinsic::log2, {$in->getType()});
-    $res = builder.CreateCall(fn, {$in});
-  }];
-}
-
-def LLVM_Prefetch : LLVM_ZeroResultOp<"intr.prefetch">,
+def LLVM_Log10Op : LLVM_UnaryIntrinsicOp<"log10">;
+def LLVM_Log2Op : LLVM_UnaryIntrinsicOp<"log2">;
+def LLVM_LogOp : LLVM_UnaryIntrinsicOp<"log">;
+def LLVM_Prefetch : LLVM_ZeroResultIntrOp<"prefetch", [0]>,
                     Arguments<(ins LLVM_Type:$addr, LLVM_Type:$rw,
-                    LLVM_Type:$hint, LLVM_Type:$cache)> {
-  let llvmBuilder = [{
-    llvm::Module *module = builder.GetInsertBlock()->getModule();
-    llvm::Function *fn = llvm::Intrinsic::getDeclaration(
-        module, llvm::Intrinsic::prefetch, $addr->getType());
-    builder.CreateCall(fn, {$addr, $rw, $hint, $cache});
-  }];
-}
+                               LLVM_Type:$hint, LLVM_Type:$cache)>;
+def LLVM_SqrtOp : LLVM_UnaryIntrinsicOp<"sqrt">;
 
 //
 // Vector Reductions.
 //
 
 def LLVM_experimental_vector_reduce_add : LLVM_VectorReduction<"add">;
 def LLVM_experimental_vector_reduce_and : LLVM_VectorReduction<"and">;
 def LLVM_experimental_vector_reduce_mul : LLVM_VectorReduction<"mul">;