[MachineVerifier][GlobalISel] Checking that generic instrs have LLTs on all vregs

Every generic machine instruction must have generic virtual registers
only, that is, have a low-level type attached to each operand.

Previously MachineVerifier would catch a type missing on an operand
only if the previous operand for the the same type index exists and
have a type attached to it and it will report it as a type mismatch.
This is incosistent behaviour and a misleading error message.

This commit makes sure MachineVerifier explicitly checks that the
types are there for every operand and if not provides a
straightforward error message.

Reviewers: qcolombet t.p.northover bogner ab

Reviewed By: qcolombet

Subscribers: rovka, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D46455

llvm-svn: 331694

2 files changed, 20 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index 0f466e4b2d1..92abd84c56b 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -1224,8 +1224,12 @@ LLT MachineInstr::getTypeToPrint(unsigned OpIdx, SmallBitVector &PrintedTypes,
   if (PrintedTypes[OpInfo.getGenericTypeIndex()])
     return LLT{};
 
-  PrintedTypes.set(OpInfo.getGenericTypeIndex());
-  return MRI.getType(Op.getReg());
+  LLT TypeToPrint = MRI.getType(Op.getReg());
+  // Don't mark the type index printed if it wasn't actually printed: maybe
+  // another operand with the same type index has an actual type attached:
+  if (TypeToPrint.isValid())
+    PrintedTypes.set(OpInfo.getGenericTypeIndex());
+  return TypeToPrint;
 }
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
diff --git a/llvm/lib/CodeGen/MachineVerifier.cpp b/llvm/lib/CodeGen/MachineVerifier.cpp
index f2cdcaaf659..ab5b389a111 100644
--- a/llvm/lib/CodeGen/MachineVerifier.cpp
+++ b/llvm/lib/CodeGen/MachineVerifier.cpp
@@ -930,16 +930,26 @@ void MachineVerifier::visitMachineInstrBefore(const MachineInstr *MI) {
 
       const MachineOperand *MO = &MI->getOperand(I);
       LLT OpTy = MRI->getType(MO->getReg());
-      if (Types[TypeIdx].isValid() && Types[TypeIdx] != OpTy)
-        report("type mismatch in generic instruction", MI);
-      Types[TypeIdx] = OpTy;
+      // Don't report a type mismatch if there is no actual mismatch, only a
+      // type missing, to reduce noise:
+      if (OpTy.isValid()) {
+        // Only the first valid type for a type index will be printed: don't
+        // overwrite it later so it's always clear which type was expected:
+        if (!Types[TypeIdx].isValid())
+          Types[TypeIdx] = OpTy;
+        else if (Types[TypeIdx] != OpTy)
+          report("Type mismatch in generic instruction", MO, I, OpTy);
+      } else {
+        // Generic instructions must have types attached to their operands.
+        report("Generic instruction is missing a virtual register type", MO, I);
+      }
     }
 
     // Generic opcodes must not have physical register operands.
     for (unsigned I = 0; I < MI->getNumOperands(); ++I) {
       const MachineOperand *MO = &MI->getOperand(I);
       if (MO->isReg() && TargetRegisterInfo::isPhysicalRegister(MO->getReg()))
-        report("Generic instruction cannot have physical register", MI);
+        report("Generic instruction cannot have physical register", MO, I);
     }
   }