Support emitting complex expressions that include entry values

This patch enables AsmPrinter support for complex expression with
entry values. It shouldn't AsmPrinter's call whether these are safe or
not but the pass who introduces the DW_OP_LLVM_entry_value. This patch
on its own has no effect on clang.

Differential Revision: https://reviews.llvm.org/D96559

Author: adrian-prantl

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp

@@ -285,20 +285,21 @@ bool DwarfExpression::addMachineRegExpression(const TargetRegisterInfo &TRI,
   // a call site parameter expression and if that expression is just a register
   // location, emit it with addBReg and offset 0, because we should emit a DWARF
   // expression representing a value, rather than a location.
-  if (!isMemoryLocation() && !HasComplexExpression &&
-      (!isParameterValue() || isEntryValue())) {
+  if ((!isParameterValue() && !isMemoryLocation() && !HasComplexExpression) ||
+      isEntryValue()) {
     for (auto &Reg : DwarfRegs) {
       if (Reg.DwarfRegNo >= 0)
         addReg(Reg.DwarfRegNo, Reg.Comment);
       addOpPiece(Reg.SubRegSize);
     }
 
-    if (isEntryValue())
+    if (isEntryValue()) {
       finalizeEntryValue();
 
-    if (isEntryValue() && !isIndirect() && !isParameterValue() &&
-        DwarfVersion >= 4)
-      emitOp(dwarf::DW_OP_stack_value);
+      if (!isIndirect() && !isParameterValue() && !HasComplexExpression &&
+          DwarfVersion >= 4)
+        emitOp(dwarf::DW_OP_stack_value);
+    }
 
     DwarfRegs.clear();
     return true;

llvm/test/DebugInfo/MIR/X86/complex-entryvalue.mir

@@ -0,0 +1,53 @@
+# RUN: llc -filetype=obj -start-after=livedebugvalues -verify-machineinstrs -march=x86-64 -o - %s | llvm-dwarfdump - | FileCheck %s
+# CHECK: DW_AT_location	(DW_OP_entry_value(DW_OP_reg5 RDI), DW_OP_constu 0xffffffff, DW_OP_and, DW_OP_lit0, DW_OP_plus)
+--- |
+  ; ModuleID = '/tmp/e.c'
+  source_filename = "/tmp/e.c"
+  target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+  target triple = "x86_64-apple-macosx11.0.0"
+  
+  ; Function Attrs: norecurse nounwind readnone ssp uwtable willreturn
+  define dso_local void @f(i32 %i) local_unnamed_addr #0 !dbg !8 {
+  entry:
+    call void @llvm.dbg.value(metadata i32 %i, metadata !14, metadata !DIExpression()), !dbg !15
+    ret void, !dbg !16
+  }
+  
+  ; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
+  declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+  
+  attributes #0 = { norecurse nounwind readnone ssp uwtable willreturn }
+  attributes #1 = { nofree nosync nounwind readnone speculatable willreturn }
+  
+  !llvm.dbg.cu = !{!0}
+  !llvm.module.flags = !{!3, !4, !5, !6}
+  
+  !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, emissionKind: FullDebug)
+  !1 = !DIFile(filename: "/tmp/e.c", directory: "/")
+  !2 = !{}
+  !3 = !{i32 7, !"Dwarf Version", i32 4}
+  !4 = !{i32 2, !"Debug Info Version", i32 3}
+  !5 = !{i32 1, !"wchar_size", i32 4}
+  !6 = !{i32 7, !"PIC Level", i32 2}
+  !8 = distinct !DISubprogram(name: "f", scope: !9, file: !9, line: 1, type: !10, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !13)
+  !9 = !DIFile(filename: "/tmp/e.c", directory: "")
+  !10 = !DISubroutineType(types: !11)
+  !11 = !{null, !12}
+  !12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+  !13 = !{!14}
+  !14 = !DILocalVariable(name: "i", arg: 1, scope: !8, file: !9, line: 1, type: !12)
+  !15 = !DILocation(line: 0, scope: !8)
+  !16 = !DILocation(line: 1, column: 16, scope: !8)
+
+...
+---
+name:            f
+body:             |
+  bb.0.entry:
+    DBG_VALUE $edi, $noreg, !14, !DIExpression(DW_OP_LLVM_entry_value, 1, DW_OP_lit0, DW_OP_plus), debug-location !15
+    frame-setup PUSH64r killed $rbp, implicit-def $rsp, implicit $rsp
+    $rbp = frame-setup MOV64rr $rsp
+    $rbp = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !16
+    RETQ debug-location !16
+
+...