[SelectionDAG] Disallow indirect "i" constraint

This allows us to delete InlineAsm::Constraint_i workarounds in
SelectionDAGISel::SelectInlineAsmMemoryOperand overrides and
TargetLowering::getInlineAsmMemConstraint overrides.

They were introduced to X86 in r237517 to prevent crashes for
constraints like "=*imr". They were later copied to other targets.

llvm/include/llvm/CodeGen/TargetLowering.h

@@ -3949,9 +3949,7 @@ public:
                                StringRef Constraint, MVT VT) const;
 
   virtual unsigned getInlineAsmMemConstraint(StringRef ConstraintCode) const {
-    if (ConstraintCode == "i")
+    if (ConstraintCode == "m")
-      return InlineAsm::Constraint_i;
-    else if (ConstraintCode == "m")
       return InlineAsm::Constraint_m;
     return InlineAsm::Constraint_Unknown;
   }

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

@@ -4498,6 +4498,12 @@ static void ChooseConstraint(TargetLowering::AsmOperandInfo &OpInfo,
     TargetLowering::ConstraintType CType =
       TLI.getConstraintType(OpInfo.Codes[i]);
 
+    // Indirect 'other' or 'immediate' constraints are not allowed.
+    if (OpInfo.isIndirect && !(CType == TargetLowering::C_Memory ||
+                               CType == TargetLowering::C_Register ||
+                               CType == TargetLowering::C_RegisterClass))
+      continue;
+
     // If this is an 'other' or 'immediate' constraint, see if the operand is
     // valid for it. For example, on X86 we might have an 'rI' constraint. If
     // the operand is an integer in the range [0..31] we want to use I (saving a

llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp

@@ -304,7 +304,6 @@ bool AArch64DAGToDAGISel::SelectInlineAsmMemoryOperand(
   switch(ConstraintID) {
   default:
     llvm_unreachable("Unexpected asm memory constraint");
-  case InlineAsm::Constraint_i:
   case InlineAsm::Constraint_m:
   case InlineAsm::Constraint_Q:
     // We need to make sure that this one operand does not end up in XZR, thus

llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp

@@ -5047,10 +5047,6 @@ SelectInlineAsmMemoryOperand(const SDValue &Op, unsigned ConstraintID,
   switch(ConstraintID) {
   default:
     llvm_unreachable("Unexpected asm memory constraint");
-  case InlineAsm::Constraint_i:
-    // FIXME: It seems strange that 'i' is needed here since it's supposed to
-    //        be an immediate and not a memory constraint.
-    LLVM_FALLTHROUGH;
   case InlineAsm::Constraint_m:
   case InlineAsm::Constraint_o:
   case InlineAsm::Constraint_Q:

llvm/lib/Target/Hexagon/HexagonISelDAGToDAG.cpp

@@ -916,7 +916,6 @@ SelectInlineAsmMemoryOperand(const SDValue &Op, unsigned ConstraintID,
   switch (ConstraintID) {
   default:
     return true;
-  case InlineAsm::Constraint_i:
   case InlineAsm::Constraint_o: // Offsetable.
   case InlineAsm::Constraint_v: // Not offsetable.
   case InlineAsm::Constraint_m: // Memory.

llvm/lib/Target/Mips/MipsISelDAGToDAG.cpp

@@ -314,7 +314,6 @@ SelectInlineAsmMemoryOperand(const SDValue &Op, unsigned ConstraintID,
   switch(ConstraintID) {
   default:
     llvm_unreachable("Unexpected asm memory constraint");
-  case InlineAsm::Constraint_i:
   case InlineAsm::Constraint_m:
   case InlineAsm::Constraint_R:
   case InlineAsm::Constraint_ZC:

llvm/lib/Target/Mips/MipsSEISelDAGToDAG.cpp

@@ -1282,10 +1282,6 @@ SelectInlineAsmMemoryOperand(const SDValue &Op, unsigned ConstraintID,
   default:
     llvm_unreachable("Unexpected asm memory constraint");
   // All memory constraints can at least accept raw pointers.
-  case InlineAsm::Constraint_i:
-    OutOps.push_back(Op);
-    OutOps.push_back(CurDAG->getTargetConstant(0, SDLoc(Op), MVT::i32));
-    return false;
   case InlineAsm::Constraint_m:
   case InlineAsm::Constraint_o:
     if (selectAddrRegImm16(Op, Base, Offset)) {

llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp

@@ -310,7 +310,6 @@ namespace {
         errs() << "ConstraintID: " << ConstraintID << "\n";
         llvm_unreachable("Unexpected asm memory constraint");
       case InlineAsm::Constraint_es:
-      case InlineAsm::Constraint_i:
       case InlineAsm::Constraint_m:
       case InlineAsm::Constraint_o:
       case InlineAsm::Constraint_Q:

llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp

@@ -173,7 +173,6 @@ void RISCVDAGToDAGISel::Select(SDNode *Node) {
 bool RISCVDAGToDAGISel::SelectInlineAsmMemoryOperand(
     const SDValue &Op, unsigned ConstraintID, std::vector<SDValue> &OutOps) {
   switch (ConstraintID) {
-  case InlineAsm::Constraint_i:
   case InlineAsm::Constraint_m:
     // We just support simple memory operands that have a single address
     // operand and need no special handling.

llvm/lib/Target/Sparc/SparcISelDAGToDAG.cpp

@@ -380,7 +380,6 @@ SparcDAGToDAGISel::SelectInlineAsmMemoryOperand(const SDValue &Op,
   SDValue Op0, Op1;
   switch (ConstraintID) {
   default: return true;
-  case InlineAsm::Constraint_i:
   case InlineAsm::Constraint_o:
   case InlineAsm::Constraint_m: // memory
    if (!SelectADDRrr(Op, Op0, Op1))

llvm/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp

@@ -218,7 +218,6 @@ void WebAssemblyDAGToDAGISel::Select(SDNode *Node) {
 bool WebAssemblyDAGToDAGISel::SelectInlineAsmMemoryOperand(
     const SDValue &Op, unsigned ConstraintID, std::vector<SDValue> &OutOps) {
   switch (ConstraintID) {
-  case InlineAsm::Constraint_i:
   case InlineAsm::Constraint_m:
     // We just support simple memory operands that just have a single address
     // operand and need no special handling.

llvm/lib/Target/X86/X86ISelDAGToDAG.cpp

@@ -5259,10 +5259,6 @@ SelectInlineAsmMemoryOperand(const SDValue &Op, unsigned ConstraintID,
   switch (ConstraintID) {
   default:
     llvm_unreachable("Unexpected asm memory constraint");
-  case InlineAsm::Constraint_i:
-    // FIXME: It seems strange that 'i' is needed here since it's supposed to
-    //        be an immediate and not a memory constraint.
-    LLVM_FALLTHROUGH;
   case InlineAsm::Constraint_o: // offsetable        ??
   case InlineAsm::Constraint_v: // not offsetable    ??
   case InlineAsm::Constraint_m: // memory

llvm/lib/Target/X86/X86ISelLowering.h

@@ -976,9 +976,7 @@ namespace llvm {
 
     unsigned
     getInlineAsmMemConstraint(StringRef ConstraintCode) const override {
-      if (ConstraintCode == "i")
+      if (ConstraintCode == "o")
-        return InlineAsm::Constraint_i;
-      else if (ConstraintCode == "o")
         return InlineAsm::Constraint_o;
       else if (ConstraintCode == "v")
         return InlineAsm::Constraint_v;