[DebugInfo] LiveDebugValues: correctly discriminate kinds of variable locations

The missing line added by this patch ensures that only spilt variable
locations are candidates for being restored from the stack. Otherwise,
register or constant-value information can be interpreted as a spill
location, through a union.

The added regression test replicates a scenario where this occurs: the
stack load from [rsp] causes the register-location DBG_VALUE to be
"restored" to rsi, when it should be left alone. See PR43058 for details.

Un x-fail a test that was suffering from this from a previous patch.

Differential Revision: https://reviews.llvm.org/D66895


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@370334 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LiveDebugValues.cpp

@@ -875,6 +875,7 @@ void LiveDebugValues::transferSpillOrRestoreInst(MachineInstr &MI,
       LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
                         << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
     } else if (TKind == TransferKind::TransferRestore &&
+               VarLocIDs[ID].Kind == VarLoc::SpillLocKind &&
                VarLocIDs[ID].Loc.SpillLocation == *Loc) {
       LLVM_DEBUG(dbgs() << "Restoring Register " << printReg(Reg, TRI) << '('
                         << VarLocIDs[ID].Var.getVar()->getName() << ")\n");

test/CodeGen/ARM/debug-info-blocks.ll

@@ -1,8 +1,5 @@
 ; RUN: llc -filetype=obj -O0 < %s | llvm-dwarfdump -v - | FileCheck %s
 
-; XFAIL: *
-; PR43058
-
 ; debug_info content
 ; CHECK: DW_AT_name {{.*}} "foobar_func_block_invoke_0"
 ; CHECK-NOT: DW_TAG_subprogram

test/DebugInfo/MIR/X86/live-debug-values-restore-collide.mir

@@ -0,0 +1,85 @@
+# RUN: llc %s -o - -run-pass=livedebugvalues -mtriple=x86_64-unknown-unknown | FileCheck %s
+#
+# This is a regression test for register/stack variable locations being
+# interpreted as each other. We place a variable location on the stack, based
+# on $rsp. We later make a memory load from $rsp. On faulty versions of LLVM
+# this gets interpreted as a stack restore of the spilt value (it's not).
+#
+# Test that LiveDebugValues does not create any new variable locations.
+#
+# CHECK-LABEL: name: baaar
+# CHECK-LABEL: bb.0.entry:
+# CHECK:       DBG_VALUE $r9d, $noreg, !{{[0-9]*}}, !DIExpression()
+# CHECK:       DBG_VALUE $rsp, 0, !{{[0-9]*}}, !DIExpression(DW_OP_plus_uconst, 16)
+# CHECK-NOT:   DBG_VALUE
+--- |
+  target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+  target triple = "x86_64-unknown-linux-gnu"
+  
+  define void @baaar() !dbg !4 {
+  entry:
+    ret void
+  }
+  
+  !llvm.module.flags = !{!0, !1}
+  !llvm.dbg.cu = !{!2}
+  
+  !0 = !{i32 2, !"Debug Info Version", i32 3}
+  !1 = !{i32 2, !"Dwarf Version", i32 4}
+  !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+  !3 = !DIFile(filename: "sheep.cpp", directory: ".")
+  !4 = distinct !DISubprogram(name: "baaar", scope: !3, file: !3, line: 1, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !8)
+  !5 = !DISubroutineType(types: !6)
+  !6 = !{!7}
+  !7 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+  !8 = !{!9}
+  !9 = !DILocalVariable(name: "moo", scope: !4, file: !3, line: 1, type: !7)
+  !10 = !DILocation(line: 1, scope: !4)
+
+...
+---
+name:            baaar
+alignment:       4
+tracksRegLiveness: true
+liveins:
+  - { reg: '$rdi', virtual-reg: '' }
+  - { reg: '$rsi', virtual-reg: '' }
+  - { reg: '$rdx', virtual-reg: '' }
+  - { reg: '$rcx', virtual-reg: '' }
+  - { reg: '$r8', virtual-reg: '' }
+  - { reg: '$r9d', virtual-reg: '' }
+frameInfo:
+  stackSize:       24
+  offsetAdjustment: -24
+  maxAlignment:    8
+  adjustsStack:    true
+  hasCalls:        true
+fixedStack:
+stack:
+  - { id: 0, name: '', type: spill-slot, offset: -16, size: 8, alignment: 8, 
+      stack-id: default, callee-saved-register: '', callee-saved-restored: true, 
+      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+  - { id: 1, name: '', type: spill-slot, offset: -32, size: 8, alignment: 8, 
+      stack-id: default, callee-saved-register: '', callee-saved-restored: true, 
+      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+body:             |
+  bb.0.entry:
+    liveins: $rcx, $rdi, $rdx, $rsi, $r8, $r9d, $rbp, $r15, $r14, $r13, $r12, $rbx
+  
+    ; Setup
+    DBG_VALUE $r9d, $noreg, !9, !DIExpression(), debug-location !10
+    $rsp = frame-setup SUB64ri8 $rsp, 24, implicit-def dead $eflags
+
+    ; Spill
+    MOV32mr $rsp, 1, $noreg, 16, $noreg, $r9d :: (store 4 into %stack.0)
+    DBG_VALUE $rsp, 0, !9, !DIExpression(DW_OP_plus_uconst, 16), debug-location !10
+
+    ; This load from the stack can be misinterpreted as a stack restore of
+    ; any DBG_VALUe pointing at $rsp.
+    $rsi = MOV64rm $rsp, 1, $noreg, 0, $noreg :: (load 8 from %stack.1)
+
+    ; Return faff
+    $eax = MOV32ri 0
+    $rsp = frame-destroy ADD64ri8 $rsp, 24, implicit-def dead $eflags
+    RETQ debug-location !10
+...