[MIRParser] Report register class errors in a deterministic order (#142928)

Author: jayfoad

llvm/lib/CodeGen/MIRParser/MIRParser.cpp

@@ -763,22 +763,25 @@ bool MIRParserImpl::setupRegisterInfo(const PerFunctionMIParsingState &PFS,
   MachineRegisterInfo &MRI = MF.getRegInfo();
   const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
 
-  bool Error = false;
+  SmallVector<std::string> Errors;
+
   // Create VRegs
   auto populateVRegInfo = [&](const VRegInfo &Info, const Twine &Name) {
     Register Reg = Info.VReg;
     switch (Info.Kind) {
     case VRegInfo::UNKNOWN:
-      error(Twine("Cannot determine class/bank of virtual register ") +
-            Name + " in function '" + MF.getName() + "'");
-      Error = true;
+      Errors.push_back(
+          (Twine("Cannot determine class/bank of virtual register ") + Name +
+           " in function '" + MF.getName() + "'")
+              .str());
       break;
     case VRegInfo::NORMAL:
       if (!Info.D.RC->isAllocatable()) {
-        error(Twine("Cannot use non-allocatable class '") +
-              TRI->getRegClassName(Info.D.RC) + "' for virtual register " +
-              Name + " in function '" + MF.getName() + "'");
-        Error = true;
+        Errors.push_back((Twine("Cannot use non-allocatable class '") +
+                          TRI->getRegClassName(Info.D.RC) +
+                          "' for virtual register " + Name + " in function '" +
+                          MF.getName() + "'")
+                             .str());
         break;
       }
 
@@ -820,7 +823,14 @@ bool MIRParserImpl::setupRegisterInfo(const PerFunctionMIParsingState &PFS,
     }
   }
 
-  return Error;
+  if (Errors.empty())
+    return false;
+
+  // Report errors in a deterministic order.
+  sort(Errors);
+  for (auto &E : Errors)
+    error(E);
+  return true;
 }
 
 bool MIRParserImpl::initializeFrameInfo(PerFunctionMIParsingState &PFS,

llvm/test/CodeGen/MIR/AMDGPU/virtreg-uses-unallocatable-class.mir

@@ -1,14 +1,13 @@
-# UNSUPPORTED: reverse_iteration
 # RUN: not llc -mtriple=amdgcn-- -mcpu=gfx900 -run-pass=none -o - %s 2>&1 | FileCheck %s
 
 # Check a diagnostic is emitted if non-allocatable classes are used
 # with virtual registers, and there's no assert.
 
-# CHECK: error: {{.*}}: Cannot use non-allocatable class 'TTMP_32' for virtual register named_use in function 'virtreg_unallocatable'
-# CHECK: error: {{.*}}: Cannot use non-allocatable class 'TTMP_32' for virtual register named_def in function 'virtreg_unallocatable'
 # CHECK: error: {{.*}}: Cannot use non-allocatable class 'TTMP_32' for virtual register 0 in function 'virtreg_unallocatable'
-# CHECK: error: {{.*}}: Cannot use non-allocatable class 'TTMP_32' for virtual register 2 in function 'virtreg_unallocatable'
 # CHECK: error: {{.*}}: Cannot use non-allocatable class 'TTMP_32' for virtual register 1 in function 'virtreg_unallocatable'
+# CHECK: error: {{.*}}: Cannot use non-allocatable class 'TTMP_32' for virtual register 2 in function 'virtreg_unallocatable'
+# CHECK: error: {{.*}}: Cannot use non-allocatable class 'TTMP_32' for virtual register named_def in function 'virtreg_unallocatable'
+# CHECK: error: {{.*}}: Cannot use non-allocatable class 'TTMP_32' for virtual register named_use in function 'virtreg_unallocatable'
 
 ---
 name: virtreg_unallocatable