[mlir] Fix crash in RewriterGen when a TypeConstraint is not given an argument

The code assumes that a TypeConstraint in the additional constraints list specifies precisely one argument.
If the user were to not specify any, it'd result in a crash. If given more than one, the additional ones were ignored.

This patch fixes the crash and disallows user errors by adding a check that a single argument is supplied to the TypeConstraint

Differential Revision: https://reviews.llvm.org/D118763

Author: zero9178

mlir/test/mlir-tblgen/rewriter-errors.td

@@ -3,6 +3,8 @@
 // RUN: not mlir-tblgen -gen-rewriters -I %S/../../include -DERROR3 %s 2>&1 | FileCheck --check-prefix=ERROR3 %s
 // RUN: not mlir-tblgen -gen-rewriters -I %S/../../include -DERROR4 %s 2>&1 | FileCheck --check-prefix=ERROR4 %s
 // RUN: not mlir-tblgen -gen-rewriters -I %S/../../include -DERROR5 %s 2>&1 | FileCheck --check-prefix=ERROR5 %s
+// RUN: not mlir-tblgen -gen-rewriters -I %S/../../include -DERROR6 %s 2>&1 | FileCheck --check-prefix=ERROR6 %s
+// RUN: not mlir-tblgen -gen-rewriters -I %S/../../include -DERROR7 %s 2>&1 | FileCheck --check-prefix=ERROR7 %s
 
 include "mlir/IR/OpBase.td"
 
@@ -49,3 +51,15 @@ def : Pat<(OpB $val, AnyI32Attr:$attr), (OpA (OpA $val, $val, (returnType (OpA $
 // ERROR5: [[@LINE+1]]:1: error: Cannot specify explicit return types in an op
 def : Pat<(OpB $val, AnyI32Attr:$attr), (OpA $val, $val, (returnType "someType()"))>;
 #endif
+
+#ifdef ERROR6
+// Check that type constraint has one argument
+// ERROR6: [[@LINE+1]]:1: error: type constraint requires exactly one argument
+def : Pat<(OpB:$result $val, $attr), (OpA $val, $val), [(AnyInteger:$result)]>;
+#endif
+
+#ifdef ERROR7
+// Check that type constraint has one argument
+// ERROR7: [[@LINE+1]]:1: error: type constraint requires exactly one argument
+def : Pat<(OpB:$opB $val, $attr), (OpA $val, $val), [(AnyInteger $opB, $val)]>;
+#endif

mlir/tools/mlir-tblgen/RewriterGen.cpp

@@ -853,6 +853,9 @@ void PatternEmitter::emitMatchLogic(DagNode tree, StringRef opName) {
 
     auto condition = constraint.getConditionTemplate();
     if (isa<TypeConstraint>(constraint)) {
+      if (entities.size() != 1)
+        PrintFatalError(loc, "type constraint requires exactly one argument");
+
       auto self = formatv("({0}.getType())",
                           symbolInfoMap.getValueAndRangeUse(entities.front()));
       emitMatchCheck(