Remove nonfunctional support for DBG_VALUE_LIST Swift async entry values.

Author: adrian-prantl

llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp

@@ -1408,10 +1408,9 @@ bool InstrRefBasedLDV::transferDebugValue(const MachineInstr &MI) {
       }
     }
 
-  if (convertToSwiftAsyncEntryValue && Expr) {
-    const_cast<MachineInstr *>(&MI)
-        ->getOperand(MI.isDebugValueList() ? 1 : 3)
-        .setMetadata(DIExpression::prepend(Expr, DIExpression::EntryValue));
+  if (convertToSwiftAsyncEntryValue && Expr && !MI.isDebugValueList()) {
+    const_cast<MachineInstr *>(&MI)->getOperand(3).setMetadata(
+        DIExpression::prepend(Expr, DIExpression::EntryValue));
     Properties.DIExpr = MI.getDebugExpression();
   }
   // END SWIFT

llvm/lib/CodeGen/LiveDebugValues/VarLocBasedImpl.cpp

@@ -2199,10 +2199,12 @@ bool VarLocBasedLDV::ExtendRanges(MachineFunction &MF,
     if (MI.isDebugValue()) {
       // In Swift async functions entry values are preferred, since they
       // can be evaluated in both live frames and virtual backtraces.
-      if (SeenDebugVars.insert(DebugVariable(MI.getDebugVariable(),
-                                             MI.getDebugExpression(),
-                                             MI.getDebugLoc()->getInlinedAt())).second  &&
-          isSwiftAsyncContext(MI)) {
+      if (SeenDebugVars
+              .insert(DebugVariable(MI.getDebugVariable(),
+                                    MI.getDebugExpression(),
+                                    MI.getDebugLoc()->getInlinedAt()))
+              .second &&
+          isSwiftAsyncContext(MI) && !MI.isDebugValueList()) {
         // If our instruction is not an entry value yet, make it an entry value.
         if (!MI.getDebugExpression()->isEntryValue()) {
           MI.getOperand(3).setMetadata(DIExpression::prepend(

llvm/test/DebugInfo/MIR/X86/swift-async-entryvalues.mir

@@ -211,14 +211,15 @@ machineFunctionInfo: {}
 body:             |
   bb.0 (%ir-block.3):
     liveins: $rdi, $rsi, $r14
-  
+
     DBG_VALUE renamable $r14, 0, !59, !DIExpression(DW_OP_deref, DW_OP_plus_uconst, 64, DW_OP_plus_uconst, 24, DW_OP_deref), debug-location !61
     frame-setup PUSH64r $r14, implicit-def $rsp, implicit $rsp
     CFI_INSTRUCTION def_cfa_offset 16
     $rsp = frame-setup SUB64ri8 $rsp, 32, implicit-def dead $eflags
     CFI_INSTRUCTION def_cfa_offset 48
     CFI_INSTRUCTION offset $r14, -16
-    DBG_VALUE renamable $r14, 0, !54, !DIExpression(DW_OP_deref, DW_OP_plus_uconst, 64, DW_OP_plus_uconst, 32), debug-location !58
+    ; This isn't supported, but it also shouldn't crash.
+    DBG_VALUE_LIST !54, !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_deref, DW_OP_plus_uconst, 64, DW_OP_plus_uconst, 32, DW_OP_stack_value), renamable $r14, debug-location !58
     $rcx = MOV64rr killed $rsi
     renamable $rax = MOV64rm renamable $r14, 1, $noreg, 0, $noreg, debug-location !47 :: (load 8 from %ir.4)
     MOV64mr $rsp, 1, $noreg, 24, $noreg, $rax :: (store 8 into %stack.0)