[ARM] Add MachineVerifier logic for some Thumb1 instructions.

[efriedma]

Summary

tMOVr and tPUSH/tPOP/tPOP_RET have register constraints which can't be expressed in TableGen, so check them explicitly. I've unfortunately run into issues with both of these recently; hopefully this saves some time for someone else in the future.

[SjoerdMeijer]

LGTM

lib/Target/ARM/ARMBaseInstrInfo.cpp

 }
 
 bool ARMBaseInstrInfo::verifyInstruction(const MachineInstr &MI,
                                          StringRef &ErrInfo) const {
   if (convertAddSubFlagsOpcode(MI.getOpcode())) {
     ErrInfo = "Pseudo flag setting opcodes only exist in Selection DAG";
     return false;
   }
+  if (MI.getOpcode() == ARM::tMOVr && !Subtarget.hasV6Ops()) {
+    // Make sure we don't generate a lo-lo mov that isn't supported.
+    if (!ARM::hGPRRegClass.contains(MI.getOperand(0).getReg()) &&
+        !ARM::hGPRRegClass.contains(MI.getOperand(1).getReg())) {
+      ErrInfo = "Non-flag-setting Thumb1 mov is v6-only";
+      return false;
+    }
+  }
+  if (MI.getOpcode() == ARM::tPUSH ||
+      MI.getOpcode() == ARM::tPOP ||
+      MI.getOpcode() == ARM::tPOP_RET) {
+    for (int i = 2, e = MI.getNumOperands(); i < e; ++i) {
+      if (MI.getOperand(i).isImplicit() ||
+          !MI.getOperand(i).isReg())
+        continue;
+      unsigned Reg = MI.getOperand(i).getReg();
+      if (Reg < ARM::R0 || Reg > ARM::R7) {
+        if (!(MI.getOpcode() == ARM::tPUSH && Reg == ARM::LR) &&
+            !(MI.getOpcode() == ARM::tPOP_RET && Reg == ARM::PC)) {
+          ErrInfo = "Unsupported register in Thumb1 push/pop";
+          return false;
+        }
+      }
+    }
+  }
   return true;
 }
 
 // LoadStackGuard has so far only been implemented for MachO. Different code
 // sequence is needed for other targets.
 void ARMBaseInstrInfo::expandLoadStackGuardBase(MachineBasicBlock::iterator MI,
                                                 unsigned LoadImmOpc,
                                                 unsigned LoadOpc) const {

test/CodeGen/ARM/machine-verifier.mir

+# RUN: not llc -mtriple=thumb -run-pass none -o /dev/null %s 2>&1 | FileCheck %s
+# This test ensures that the MIR parser runs the machine verifier after parsing.
+
+--- |
+
+  define i32 @inc(i32 %a) {
+  entry:
+    ret i32 %a
+  }
+
+...
+---
+name: inc
+tracksRegLiveness: true
+body: |
+  bb.0.entry:
+   ; CHECK: *** Bad machine code: Unsupported register in Thumb1 push/pop ***
+   frame-setup tPUSH 14, $noreg, undef $r12, killed $lr, implicit-def $sp, implicit $sp
+
+   ; CHECK: *** Bad machine code: Non-flag-setting Thumb1 mov is v6-only ***
+   $r2 = tMOVr killed $r6, 14, $noreg
+...