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

[zero9178]

Summary

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

[Mogball]

+1 I have stepped on this crash before

[jpienaar]

Thanks!

[Chia-hungDuan]

mlir/tools/mlir-tblgen/RewriterGen.cpp

856–858

Lint: Simple single-statement body doesn't need bracket

[zero9178]

mlir/tools/mlir-tblgen/RewriterGen.cpp

856–858

Thank you! Fixed it in the final commit

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

 // RUN: not mlir-tblgen -gen-rewriters -I %S/../../include -DERROR1 %s 2>&1 | FileCheck --check-prefix=ERROR1 %s
 // RUN: not mlir-tblgen -gen-rewriters -I %S/../../include -DERROR2 %s 2>&1 | FileCheck --check-prefix=ERROR2 %s
 // 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"
 
 // Check using the dialect name as the namespace
 def A_Dialect : Dialect {
   let name = "a";
 }
 

 def : Pat<(OpB $val, AnyI32Attr:$attr), (OpA (OpA $val, $val, (returnType (OpA $val, $val))), $val)>;
 #endif
 
 #ifdef ERROR5
 // Check that trying to specify explicit types at the root node fails.
 // 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

void PatternEmitter::emitMatchLogic(DagNode tree, StringRef opName) {
   emitMatch(tree, opName, depth);
 
   for (auto &appliedConstraint : pattern.getConstraints()) {
     auto &constraint = appliedConstraint.constraint;
     auto &entities = appliedConstraint.entities;
 
     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(
           opName, tgfmt(condition, &fmtCtx.withSelf(self.str())),
           formatv("\"value entity '{0}' failed to satisfy constraint: '{1}'\"",
                   entities.front(), escapeString(constraint.getSummary())));
 
     } else if (isa<AttrConstraint>(constraint)) {