[llvm] 536b9eb - [DebugInfo][InstrRef] Add extra indirection for NRVO tests

[Jeremy Morse via llvm-commits]

Author: Jeremy Morse
Date: 2021-11-25T21:43:38Z
New Revision: 536b9eb31e9333bcee3d20d694f7cb12d1ff3d89

URL: https://github.com/llvm/llvm-project/commit/536b9eb31e9333bcee3d20d694f7cb12d1ff3d89
DIFF: https://github.com/llvm/llvm-project/commit/536b9eb31e9333bcee3d20d694f7cb12d1ff3d89.diff

LOG: [DebugInfo][InstrRef] Add extra indirection for NRVO tests

In some scenarios, usually involving NRVO, we can issue indirect DBG_VALUEs
after SelectionDAG, even in instruction referencing mode (if the variable
is an argument). If the corresponding argument value is spilt to the stack,
then we have:
 * Indirection from it being on the stack,
 * Indirection from it being a dbg.declare or a dbg.addr.

However InstrRefBasedLDV only emits one level of indirection. This patch
adds the second, by adding an extra DW_OP_deref if necessary. The two
tests modified fail otherwise -- they feature some NRVO, and require two
levels of indirection to be correct.

Differential Revision: https://reviews.llvm.org/D114364

Added: 
    

Modified: 
    llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
    llvm/test/DebugInfo/X86/spill-indirect-nrvo.ll
    llvm/test/DebugInfo/X86/spill-nontrivial-param.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
index eff8ec7900383..5b488d8f282b8 100644
--- a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
@@ -836,6 +836,15 @@ MachineInstrBuilder MLocTracker::emitLoc(Optional<LocIdx> MLoc,
       unsigned Base = Spill.SpillBase;
       MIB.addReg(Base);
       MIB.addImm(0);
+
+      // Being on the stack makes this location indirect; if it was _already_
+      // indirect though, we need to add extra indirection. See this test for
+      // a scenario where this happens:
+      //     llvm/test/DebugInfo/X86/spill-nontrivial-param.ll
+      if (Properties.Indirect) {
+        std::vector<uint64_t> Elts = {dwarf::DW_OP_deref};
+        Expr = DIExpression::append(Expr, Elts);
+      }
     } else {
       // This is a stack location with a weird subregister offset: emit an undef
       // DBG_VALUE instead.

diff  --git a/llvm/test/DebugInfo/X86/spill-indirect-nrvo.ll b/llvm/test/DebugInfo/X86/spill-indirect-nrvo.ll
index f47e6dc2e9e80..a920f31cfa9ab 100644
--- a/llvm/test/DebugInfo/X86/spill-indirect-nrvo.ll
+++ b/llvm/test/DebugInfo/X86/spill-indirect-nrvo.ll
@@ -1,5 +1,7 @@
 ; RUN: llc < %s -experimental-debug-variable-locations=false | FileCheck -check-prefixes=CHECK,OPT %s
 ; RUN: llc -O0 < %s -experimental-debug-variable-locations=false | FileCheck -check-prefixes=CHECK,OPTNONE %s
+; RUN: llc < %s -experimental-debug-variable-locations=true | FileCheck -check-prefixes=CHECK,OPT %s
+; RUN: llc -O0 < %s -experimental-debug-variable-locations=true | FileCheck -check-prefixes=CHECK,OPTNONE %s
 
 ; Make sure we insert DW_OP_deref when spilling indirect DBG_VALUE instructions.
 

diff  --git a/llvm/test/DebugInfo/X86/spill-nontrivial-param.ll b/llvm/test/DebugInfo/X86/spill-nontrivial-param.ll
index 3dddb62a93e81..f6c0cb294d8ba 100644
--- a/llvm/test/DebugInfo/X86/spill-nontrivial-param.ll
+++ b/llvm/test/DebugInfo/X86/spill-nontrivial-param.ll
@@ -1,4 +1,5 @@
 ; RUN: llc < %s -experimental-debug-variable-locations=false | FileCheck %s
+; RUN: llc < %s -experimental-debug-variable-locations=true | FileCheck %s
 
 ; Make sure we insert DW_OP_deref when spilling indirect DBG_VALUE instructions.
 ; In this example, 'nt' is passed by address because it is not trivially