From 1172c76018d654e40f0bab94839031fce609b1ce Mon Sep 17 00:00:00 2001
From: Adrian Prantl <aprantl@apple.com>
Date: Thu, 11 Feb 2021 16:07:19 -0800
Subject: [PATCH] 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
---
 lib/CodeGen/AsmPrinter/DwarfExpression.cpp    | 13 ++---
 test/DebugInfo/MIR/X86/complex-entryvalue.mir | 53 +++++++++++++++++++
 2 files changed, 60 insertions(+), 6 deletions(-)
 create mode 100644 test/DebugInfo/MIR/X86/complex-entryvalue.mir

diff --git a/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index aee0f4cedc0..3e664b375c3 100644
--- a/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/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;
diff --git a/test/DebugInfo/MIR/X86/complex-entryvalue.mir b/test/DebugInfo/MIR/X86/complex-entryvalue.mir
new file mode 100644
index 00000000000..cc7e6dbc08e
--- /dev/null
+++ b/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
+
+...