[TableGen] Fix null pointer dereferences in TreePattern::ParseTreePattern()

[SweetVishnya]

Summary

Bugs were found by Svace static analysis tool. Null pointers are
dereferenced right after error checking that does not return from
function.

[arsenm]

LGTM. Tests would be nice

[SweetVishnya]

In D147706#4252375, @arsenm wrote:

LGTM. Tests would be nice

These bugs were found by a static analyzer based on the fact that null pointer is checked right before dereference. I don't really know how to hand-craft test cases for these errors.

[SweetVishnya]

Can we merge this fix into main branch?

[arsenm]

In D147706#4330642, @SweetVishnya wrote:

Can we merge this fix into main branch?

Don’t see why not

[arsenm]

In D147706#4330830, @arsenm wrote:

In D147706#4330642, @SweetVishnya wrote:

Can we merge this fix into main branch?

Don’t see why not

Have you opened an issue to merge it?

[SweetVishnya]

In D147706#4330840, @arsenm wrote:

In D147706#4330830, @arsenm wrote:

In D147706#4330642, @SweetVishnya wrote:

Can we merge this fix into main branch?

Don’t see why not

Have you opened an issue to merge it?

No, I haven't. I thought that patches are merged some time after approval. What further actions should I take?

[craig.topper]

In D147706#4330864, @SweetVishnya wrote:

In D147706#4330840, @arsenm wrote:

In D147706#4330830, @arsenm wrote:

In D147706#4330642, @SweetVishnya wrote:

Can we merge this fix into main branch?

Don’t see why not

Have you opened an issue to merge it?

No, I haven't. I thought that patches are merged some time after approval. What further actions should I take?

Patches are usually merged by person submitting the patch. If you don't have commit access say so and one of the reviewers can commit it for you. Please provide your name and email as it should appear in the git commit log.

[SweetVishnya]

In D147706#4330879, @craig.topper wrote:

In D147706#4330864, @SweetVishnya wrote:

In D147706#4330840, @arsenm wrote:

In D147706#4330830, @arsenm wrote:

In D147706#4330642, @SweetVishnya wrote:

Can we merge this fix into main branch?

Don’t see why not

Have you opened an issue to merge it?

No, I haven't. I thought that patches are merged some time after approval. What further actions should I take?

Patches are usually merged by person submitting the patch. If you don't have commit access say so and one of the reviewers can commit it for you. Please provide your name and email as it should appear in the git commit log.

Yes, I don't have a commit access. Can you commit the patch for me, please? My name is "Alexey Vishnyakov" and email is "[e-mail]"

llvm/utils/TableGen/CodeGenDAGPatterns.cpp

if (isa<IntInit>(TheInit) || isa<BitInit>(TheInit)) {
     return makeIntrusiveRefCnt<TreePatternNode>(TheInit, 1);
   }
 
   if (BitsInit *BI = dyn_cast<BitsInit>(TheInit)) {
     // Turn this into an IntInit.
     Init *II = BI->convertInitializerTo(IntRecTy::get(RK));
     if (!II || !isa<IntInit>(II))
       error("Bits value must be constants!");
-    return ParseTreePattern(II, OpName);
+    return II ? ParseTreePattern(II, OpName) : nullptr;
   }
 
   DagInit *Dag = dyn_cast<DagInit>(TheInit);
   if (!Dag) {
     TheInit->print(errs());
     error("Pattern has unexpected init kind!");
+    return nullptr;
   }
   DefInit *OpDef = dyn_cast<DefInit>(Dag->getOperator());
-  if (!OpDef) error("Pattern has unexpected operator type!");
+  if (!OpDef) {
+    error("Pattern has unexpected operator type!");
+    return nullptr;
+  }
   Record *Operator = OpDef->getDef();
 
   if (Operator->isSubClassOf("ValueType")) {
     // If the operator is a ValueType, then this must be "type cast" of a leaf
     // node.
     if (Dag->getNumArgs() != 1)
       error("Type cast only takes one operand!");
 
if (Pat->getOperator()->getName() == "implicit") {
     for (unsigned i = 0, e = Pat->getNumChildren(); i != e; ++i) {
       TreePatternNode *Dest = Pat->getChild(i);
       if (!Dest->isLeaf())
         I.error("implicitly defined value should be a register!");
 
       DefInit *Val = dyn_cast<DefInit>(Dest->getLeafValue());
       if (!Val || !Val->getDef()->isSubClassOf("Register"))
         I.error("implicitly defined value should be a register!");
+      if (Val)
         InstImpResults.push_back(Val->getDef());
     }
     return;
   }
 
   if (Pat->getOperator()->getName() != "set") {
     // If this is not a set, verify that the children nodes are not void typed,
     // and recurse.
     for (unsigned i = 0, e = Pat->getNumChildren(); i != e; ++i) {