From 8763c0c5b7a566d2fe9476259aa346640b0a9deb Mon Sep 17 00:00:00 2001
From: Matthias Braun <matze@braunis.de>
Date: Wed, 31 Oct 2018 17:18:41 +0000
Subject: [PATCH] MachineModuleInfo: Initialize DbgInfoAvailable depending on
 debug_cus existing

Before this patch DbgInfoAvailable was set to true in
DwarfDebug::beginModule() or CodeViewDebug::CodeViewDebug(). This made
MIR testing weird since passes would suddenly stop dealing with debug
info just because we stopped the pipeline before the debug printers.

This patch changes the logic to initialize DbgInfoAvailable based on the
fact that debug_compile_units exist in the llvm Module. The debug
printers may then override it with false in case of debug printing being
disabled.

Differential Revision: https://reviews.llvm.org/D53885

llvm-svn: 345740
---
 llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp |  1 +
 llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp    |  7 +++++--
 llvm/lib/CodeGen/MachineModuleInfo.cpp        |  3 ++-
 llvm/test/CodeGen/AArch64/fast-isel-dbg.ll    | 26 ++++++++++++++++++++++++++
 4 files changed, 34 insertions(+), 3 deletions(-)
 create mode 100644 llvm/test/CodeGen/AArch64/fast-isel-dbg.ll

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 3b503b6..42259d4 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -117,6 +117,7 @@ CodeViewDebug::CodeViewDebug(AsmPrinter *AP)
   if (!MMI->getModule()->getNamedMetadata("llvm.dbg.cu") ||
       !AP->getObjFileLowering().getCOFFDebugSymbolsSection()) {
     Asm = nullptr;
+    MMI->setDebugInfoAvailability(false);
     return;
   }
   // Tell MMI that we have debug info.
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 3a1e548..2807734 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -701,15 +701,18 @@ sortGlobalExprs(SmallVectorImpl<DwarfCompileUnit::GlobalExpr> &GVEs) {
 void DwarfDebug::beginModule() {
   NamedRegionTimer T(DbgTimerName, DbgTimerDescription, DWARFGroupName,
                      DWARFGroupDescription, TimePassesIsEnabled);
-  if (DisableDebugInfoPrinting)
+  if (DisableDebugInfoPrinting) {
+    MMI->setDebugInfoAvailability(false);
     return;
+  }
 
   const Module *M = MMI->getModule();
 
   unsigned NumDebugCUs = std::distance(M->debug_compile_units_begin(),
                                        M->debug_compile_units_end());
   // Tell MMI whether we have debug info.
-  MMI->setDebugInfoAvailability(NumDebugCUs > 0);
+  assert(MMI->hasDebugInfo() == (NumDebugCUs > 0) &&
+         "DebugInfoAvailabilty initialized unexpectedly");
   SingleCU = NumDebugCUs == 1;
   DenseMap<DIGlobalVariable *, SmallVector<DwarfCompileUnit::GlobalExpr, 1>>
       GVMap;
diff --git a/llvm/lib/CodeGen/MachineModuleInfo.cpp b/llvm/lib/CodeGen/MachineModuleInfo.cpp
index 639cd80..ce55690 100644
--- a/llvm/lib/CodeGen/MachineModuleInfo.cpp
+++ b/llvm/lib/CodeGen/MachineModuleInfo.cpp
@@ -206,10 +206,11 @@ MachineModuleInfo::~MachineModuleInfo() = default;
 bool MachineModuleInfo::doInitialization(Module &M) {
   ObjFileMMI = nullptr;
   CurCallSite = 0;
-  DbgInfoAvailable = UsesVAFloatArgument = UsesMorestackAddr = false;
+  UsesVAFloatArgument = UsesMorestackAddr = false;
   HasSplitStack = HasNosplitStack = false;
   AddrLabelSymbols = nullptr;
   TheModule = &M;
+  DbgInfoAvailable = !empty(M.debug_compile_units());
   return false;
 }
 
diff --git a/llvm/test/CodeGen/AArch64/fast-isel-dbg.ll b/llvm/test/CodeGen/AArch64/fast-isel-dbg.ll
new file mode 100644
index 0000000..4d26b91
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/fast-isel-dbg.ll
@@ -0,0 +1,26 @@
+; RUN: llc -o - %s -fast-isel -stop-before=expand-isel-pseudos | FileCheck %s
+; Make sure fast-isel produces DBG_VALUE instructions even if no debug printer
+; is scheduled because of -stop-before.
+target triple="aarch64--"
+
+; CHECK-LABEL: name: func
+; CHECK: DBG_VALUE
+define void @func(i32 %a) !dbg !4 {
+  call void @llvm.dbg.declare(metadata i32 %a, metadata !5, metadata !DIExpression()), !dbg !7
+  ret void
+}
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #0
+attributes #0 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly)
+!1 = !DIFile(filename: "fast-isel-dbg.ll", directory: "/")
+!2 = !{i32 2, !"Dwarf Version", i32 4}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = distinct !DISubprogram(name: "func", scope: null, isLocal: false, isDefinition: true, isOptimized: false, unit: !0)
+!5 = !DILocalVariable(name: "a", arg: 1, scope: !4, file: !1, line: 17, type: !6)
+!6 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
+!7 = !DILocation(line: 17, scope: !4)
-- 
2.7.4