GlobalISel: verify that a COPY is trivial when created.

Without this check, COPY instructions can actually be one of the generic casts
in disguise. That's confusing and bad.

At some point during ISel this restriction has to be relaxed since the fully
selected instructions will usually use COPY for those purposes. Right now I
think it's possible that relaxation occurs during RegBankSelect (hence the
change there). I'm not convinced that's where it belongs long-term though.

llvm-svn: 306470

2 files changed, 10 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
index 6fcc3907dd2..ff3e53ad771 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -268,6 +268,8 @@ MachineInstrBuilder MachineIRBuilder::buildBrIndirect(unsigned Tgt) {
 }
 
 MachineInstrBuilder MachineIRBuilder::buildCopy(unsigned Res, unsigned Op) {
+  assert(MRI->getType(Res) == LLT() || MRI->getType(Op) == LLT() ||
+         MRI->getType(Res) == MRI->getType(Op));
   return buildInstr(TargetOpcode::COPY).addDef(Res).addUse(Op);
 }
 
@@ -384,7 +386,6 @@ MachineInstrBuilder MachineIRBuilder::buildZExtOrTrunc(unsigned Res,
   return buildInstr(Opcode).addDef(Res).addUse(Op);
 }
 
-
 MachineInstrBuilder MachineIRBuilder::buildCast(unsigned Dst, unsigned Src) {
   LLT SrcTy = MRI->getType(Src);
   LLT DstTy = MRI->getType(Dst);
@@ -483,7 +484,7 @@ MachineInstrBuilder MachineIRBuilder::buildMerge(unsigned Res,
 #endif
 
   if (Ops.size() == 1)
-    return buildCopy(Res, Ops[0]);
+    return buildCast(Res, Ops[0]);
 
   MachineInstrBuilder MIB = buildInstr(TargetOpcode::G_MERGE_VALUES);
   MIB.addDef(Res);
diff --git a/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp b/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp
index 6ee69d5274d..677941dbbf6 100644
--- a/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp
@@ -154,9 +154,11 @@ bool RegBankSelect::repairReg(
           TargetRegisterInfo::isPhysicalRegister(Dst)) &&
          "We are about to create several defs for Dst");
 
-  // Build the instruction used to repair, then clone it at the right places.
-  MachineInstr *MI = MIRBuilder.buildCopy(Dst, Src);
-  MI->removeFromParent();
+  // Build the instruction used to repair, then clone it at the right
+  // places. Avoiding buildCopy bypasses the check that Src and Dst have the
+  // same types because the type is a placeholder when this function is called.
+  MachineInstr *MI =
+      MIRBuilder.buildInstrNoInsert(TargetOpcode::COPY).addDef(Dst).addUse(Src);
   DEBUG(dbgs() << "Copy: " << PrintReg(Src) << " to: " << PrintReg(Dst)
                << '\n');
   // TODO:
@@ -556,9 +558,11 @@ bool RegBankSelect::applyMapping(
       llvm_unreachable("Other kind should not happen");
     }
   }
+
   // Second, rewrite the instruction.
   DEBUG(dbgs() << "Actual mapping of the operands: " << OpdMapper << '\n');
   RBI->applyMapping(OpdMapper);
+
   return true;
 }