diff --git a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
index 74f6e6e8fbe7..72d025ecb2f3 100644
--- a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
@@ -1293,41 +1293,16 @@ bool InstrRefBasedLDV::transferDebugPHI(MachineInstr &MI) {
     if (!SpillNo)
       return EmitBadPHI();
 
-    // Problem: what value should we extract from the stack? LLVM does not
-    // record what size the last store to the slot was, and it would become
-    // sketchy after stack slot colouring anyway. Take a look at what values
-    // are stored on the stack, and pick the largest one that wasn't def'd
-    // by a spill (i.e., the value most likely to have been def'd in a register
-    // and then spilt.
-    std::array<unsigned, 4> CandidateSizes = {64, 32, 16, 8};
-    Optional<ValueIDNum> Result = None;
-    Optional<LocIdx> SpillLoc = None;
-    for (unsigned CS : CandidateSizes) {
-      unsigned SpillID = MTracker->getLocID(*SpillNo, {CS, 0});
-      SpillLoc = MTracker->getSpillMLoc(SpillID);
-      ValueIDNum Val = MTracker->readMLoc(*SpillLoc);
-      // If this value was defined in it's own position, then it was probably
-      // an aliasing index of a small value that was spilt.
-      if (Val.getLoc() != SpillLoc->asU64()) {
-        Result = Val;
-        break;
-      }
-    }
+    // Any stack location DBG_PHI should have an associate bit-size.
+    assert(MI.getNumOperands() == 3 && "Stack DBG_PHI with no size?");
+    unsigned slotBitSize = MI.getOperand(2).getImm();
 
-    // If we didn't find anything, we're probably looking at a PHI, or a memory
-    // store folded into an instruction. FIXME: Take a guess that's it's 64
-    // bits. This isn't ideal, but tracking the size that the spill is
-    // "supposed" to be is more complex, and benefits a small number of
-    // locations.
-    if (!Result) {
-      unsigned SpillID = MTracker->getLocID(*SpillNo, {64, 0});
-      SpillLoc = MTracker->getSpillMLoc(SpillID);
-      Result = MTracker->readMLoc(*SpillLoc);
-    }
+    unsigned SpillID = MTracker->getLocID(*SpillNo, {slotBitSize, 0});
+    LocIdx SpillLoc = MTracker->getSpillMLoc(SpillID);
+    ValueIDNum Result = MTracker->readMLoc(SpillLoc);
 
     // Record this DBG_PHI for later analysis.
-    auto DbgPHI =
-        DebugPHIRecord({InstrNum, MI.getParent(), *Result, *SpillLoc});
+    auto DbgPHI = DebugPHIRecord({InstrNum, MI.getParent(), Result, SpillLoc});
     DebugPHINumToValue.push_back(DbgPHI);
   } else {
     // Else: if the operand is neither a legal register or a stack slot, then
diff --git a/llvm/lib/CodeGen/LiveDebugVariables.cpp b/llvm/lib/CodeGen/LiveDebugVariables.cpp
index ce350b78d753..320e68241e4e 100644
--- a/llvm/lib/CodeGen/LiveDebugVariables.cpp
+++ b/llvm/lib/CodeGen/LiveDebugVariables.cpp
@@ -1850,16 +1850,33 @@ void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
       const TargetRegisterClass *TRC = MRI.getRegClass(Reg);
       unsigned SpillSize, SpillOffset;
 
-      // Test whether this location is legal with the given subreg.
+      unsigned regSizeInBits = TRI->getRegSizeInBits(*TRC);
+      if (SubReg)
+        regSizeInBits = TRI->getSubRegIdxSize(SubReg);
+
+      // Test whether this location is legal with the given subreg. If the
+      // subregister has a nonzero offset, drop this location, it's too complex
+      // to describe. (TODO: future work).
       bool Success =
           TII->getStackSlotRange(TRC, SubReg, SpillSize, SpillOffset, *MF);
 
-      if (Success) {
+      if (Success && SpillOffset == 0) {
         auto Builder = BuildMI(*OrigMBB, OrigMBB->begin(), DebugLoc(),
                                TII->get(TargetOpcode::DBG_PHI));
         Builder.addFrameIndex(VRM->getStackSlot(Reg));
         Builder.addImm(InstNum);
+        // Record how large the original value is. The stack slot might be
+        // merged and altered during optimisation, but we will want to know how
+        // large the value is, at this DBG_PHI.
+        Builder.addImm(regSizeInBits);
       }
+
+      LLVM_DEBUG(
+      if (SpillOffset != 0) {
+        dbgs() << "DBG_PHI for Vreg " << Reg << " subreg " << SubReg <<
+                  " has nonzero offset\n";
+      }
+      );
     }
     // If there was no mapping for a value ID, it's optimized out. Create no
     // DBG_PHI, and any variables using this value will become optimized out.
diff --git a/llvm/test/DebugInfo/MIR/InstrRef/dbg-phis-in-ldv2.mir b/llvm/test/DebugInfo/MIR/InstrRef/dbg-phis-in-ldv2.mir
new file mode 100644
index 000000000000..ac42364ae22f
--- /dev/null
+++ b/llvm/test/DebugInfo/MIR/InstrRef/dbg-phis-in-ldv2.mir
@@ -0,0 +1,128 @@
+# RUN: llc %s -o - -mtriple=x86_64-unknown-unknown \
+# RUN:    -experimental-debug-variable-locations -run-pass=livedebugvalues\
+# RUN:    | FileCheck %s
+#
+# Test that a DBG_INSTR_REF that refers to a DBG_PHI, will be translated into a
+# DBG_VALUE of the value read at that DBG_PHI -- in this test, when the value
+# is on the stack.
+# 
+--- |
+  target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+  target triple = "x86_64-unknown-linux-gnu"
+  
+  define dso_local i32 @foo(i64 %bar, i64 %baz) !dbg !7 {
+    ret i32 0
+  }
+  
+  declare dso_local void @ext(i64)
+  
+  declare dso_local i64 @getlong()
+  
+  !llvm.dbg.cu = !{!0}
+  !llvm.module.flags = !{!3, !4, !5}
+  !llvm.ident = !{!6}
+  
+  !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
+  !1 = !DIFile(filename: "test.c", directory: "/tmp/out.c")
+  !2 = !{}
+  !3 = !{i32 7, !"Dwarf Version", i32 4}
+  !4 = !{i32 2, !"Debug Info Version", i32 3}
+  !5 = !{i32 1, !"wchar_size", i32 4}
+  !6 = !{!""}
+  !7 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 3, type: !8, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+  !8 = !DISubroutineType(types: !9)
+  !9 = !{!10, !11, !11}
+  !10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+  !11 = !DIBasicType(name: "long int", size: 64, encoding: DW_ATE_signed)
+  !12 = !DILocalVariable(name: "bar", arg: 1, scope: !7, file: !1, line: 3, type: !11)
+  !13 = !DILocation(line: 0, scope: !7)
+  !14 = !DILocalVariable(name: "baz", arg: 2, scope: !7, file: !1, line: 3, type: !11)
+  !19 = distinct !DILexicalBlock(scope: !7, file: !1, line: 8, column: 7)
+  !26 = !DILocation(line: 13, column: 3, scope: !7)
+
+...
+---
+name:            foo
+alignment:       16
+tracksRegLiveness: true
+liveins:
+  - { reg: '$rdi' }
+  - { reg: '$rsi' }
+frameInfo:
+  stackSize:       24
+  offsetAdjustment: -24
+  maxAlignment:    1
+  adjustsStack:    true
+  hasCalls:        true
+  maxCallFrameSize: 0
+  cvBytesOfCalleeSavedRegisters: 16
+fixedStack:
+  - { id: 0, type: spill-slot, offset: -24, size: 8, alignment: 8, callee-saved-register: '$rbx' }
+  - { id: 1, type: spill-slot, offset: -16, size: 8, alignment: 16, callee-saved-register: '$r14' }
+machineFunctionInfo: {}
+stack:
+  - { id: 0, name: '', type: spill-slot, offset: 0, 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:
+    liveins: $rdi, $rsi, $r14, $rbx
+    ; CHECK-LABEL: bb.0:
+  
+    $r14 = MOV64rr $rsi
+    $rbx = MOV64rr $rdi
+    $rax = MOV64ri 0
+    MOV64mr $rsp, 1, $noreg, 16, $noreg, $rax :: (store 8 into %stack.0)
+    $rax = MOV64ri 0
+
+    ;; A DBG_PHI of the stack should resolve to the stack location.
+    DBG_PHI %stack.0, 1, 64
+
+    ;; Reload value, clobber stack location.
+    $rcx = MOV64rm $rsp, 1, $noreg, 8, $noreg :: (load 8 from %stack.0)
+    MOV64mr $rsp, 1, $noreg, 16, $noreg, $rax :: (store 8 into %stack.0)
+
+    ;; This should resolve to the loaded register.
+    DBG_INSTR_REF 1, 0, !12, !DIExpression(), debug-location !13
+    ; CHECK:      DBG_INSTR_REF 1, 0,
+    ; CHECK-NEXT: DBG_VALUE $rcx
+
+    ;; And if we say it's a smaller size, we should be able to pick out smaller
+    ;; subregisters within the stack slot.
+    DBG_PHI %stack.0, 2, 32
+    $rax = MOV64ri 0
+    $rcx = MOV64rm $rsp, 1, $noreg, 8, $noreg :: (load 8 from %stack.0)
+    MOV64mr $rsp, 1, $noreg, 16, $noreg, $rax :: (store 8 into %stack.0)
+
+    ;; This should pick out the 32 bit value.
+    DBG_INSTR_REF 2, 0, !12, !DIExpression(), debug-location !13
+    ; CHECK:      DBG_INSTR_REF 2, 0,
+    ; CHECK-NEXT: DBG_VALUE $ecx
+
+    ;; Try all the other subregs.
+    DBG_PHI %stack.0, 3, 16
+    $rax = MOV64ri 0
+    $rcx = MOV64rm $rsp, 1, $noreg, 8, $noreg :: (load 8 from %stack.0)
+    MOV64mr $rsp, 1, $noreg, 16, $noreg, $rax :: (store 8 into %stack.0)
+
+    DBG_INSTR_REF 3, 0, !12, !DIExpression(), debug-location !13
+    ; CHECK:      DBG_INSTR_REF 3, 0,
+    ; CHECK-NEXT: DBG_VALUE $cx
+
+    DBG_PHI %stack.0, 4, 8
+    $rax = MOV64ri 0
+    $rcx = MOV64rm $rsp, 1, $noreg, 8, $noreg :: (load 8 from %stack.0)
+    MOV64mr $rsp, 1, $noreg, 16, $noreg, $rax :: (store 8 into %stack.0)
+
+    DBG_INSTR_REF 4, 0, !12, !DIExpression(), debug-location !13
+    ; CHECK:      DBG_INSTR_REF 4, 0,
+    ; CHECK-NEXT: DBG_VALUE $cl
+
+    ;; We can't, at this time, describe subregister fields with nonzero offset.
+    ;; It's easily achieved by attaching more data to stack DBG_PHIs, but it's
+    ;; not clear that LLVM will ever merge registers to generate such locations.
+
+    RET64 implicit $eax, debug-location !26
+
+...
diff --git a/llvm/test/DebugInfo/MIR/InstrRef/phi-on-stack-coalesced.mir b/llvm/test/DebugInfo/MIR/InstrRef/phi-on-stack-coalesced.mir
new file mode 100644
index 000000000000..a0b6d796ce64
--- /dev/null
+++ b/llvm/test/DebugInfo/MIR/InstrRef/phi-on-stack-coalesced.mir
@@ -0,0 +1,156 @@
+# RUN: llc %s -o - -mtriple=x86_64-unknown-unknown \
+# RUN:    -experimental-debug-variable-locations \
+# RUN:    -start-before=phi-node-elimination -stop-after=virtregrewriter \
+# RUN:    | FileCheck %s
+#
+# Like phi-through-regalloc.mir, pass a PHI node into register allocation, and
+# test that it correctly comes out, in a stack slot. In this test the desired
+# value is a 16 bit copy of an argument, and the PHI register class is 16 bits.
+# It's subsequently coalesced into a larger vreg, which is then spilt as a 32
+# bit value.
+# Test that the coalescing happens (32 bits stored and loaded), but that we
+# record in the relevant DBG_PHI that the original value was 16 bits in size.
+# This avoids later ambiguity about how large the value on the stack is.
+
+--- |
+  ; ModuleID = 'promoted.ll'
+  source_filename = "test.c"
+  target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+  target triple = "x86_64-unknown-linux-gnu"
+
+  define dso_local i32 @foo(i32 %bar, i32 %baz) !dbg !7 {
+  entry:
+    ret i32 0, !dbg !19
+  }
+
+  declare dso_local i32 @ext(i32)
+
+  ; Function Attrs: nounwind readnone speculatable willreturn
+  declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+  !llvm.dbg.cu = !{!0}
+  !llvm.module.flags = !{!3, !4, !5}
+  !llvm.ident = !{!6}
+
+  !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
+  !1 = !DIFile(filename: "test.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 = !{!"."}
+  !7 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 2, type: !8, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+  !8 = !DISubroutineType(types: !9)
+  !9 = !{!10, !10, !10}
+  !10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+  !11 = !DILocalVariable(name: "bar", arg: 1, scope: !7, file: !1, line: 2, type: !10)
+  !12 = !DILocation(line: 0, scope: !7)
+  !13 = !DILocalVariable(name: "baz", arg: 2, scope: !7, file: !1, line: 2, type: !10)
+  !14 = !DILocalVariable(name: "either", scope: !7, file: !1, line: 3, type: !10)
+  !15 = !DILocation(line: 4, column: 7, scope: !16)
+  !16 = distinct !DILexicalBlock(scope: !7, file: !1, line: 4, column: 7)
+  !17 = !DILocation(line: 4, column: 7, scope: !7)
+  !18 = !DILocation(line: 0, scope: !16)
+  !19 = !DILocation(line: 9, column: 3, scope: !7)
+
+...
+---
+name:            foo
+alignment:       16
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: gr16 }
+  - { id: 1, class: gr32 }
+  - { id: 2, class: gr32 }
+  - { id: 3, class: gr32 }
+  - { id: 4, class: gr32 }
+liveins:
+  - { reg: '$edi', virtual-reg: '%1' }
+  - { reg: '$esi', virtual-reg: '%2' }
+frameInfo:
+  maxAlignment:    1
+  hasCalls:        true
+machineFunctionInfo: {}
+body:             |
+  ; CHECK-LABEL: bb.0:
+  ; CHECK:       MOV32mr %stack.0, 1, $noreg, 0, $noreg, $edi
+  bb.0:
+    successors: %bb.2(0x50000000), %bb.1(0x30000000)
+    liveins: $edi, $esi
+
+    DBG_VALUE $edi, $noreg, !11, !DIExpression(), debug-location !12
+    DBG_VALUE $esi, $noreg, !13, !DIExpression(), debug-location !12
+    %2:gr32 = COPY killed $esi
+    %1:gr32 = COPY killed $edi
+    %5:gr16 = COPY %1.sub_16bit
+    %6:gr16 = COPY %1.sub_16bit
+    ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp, debug-location !15
+    %3:gr32 = MOV32r0 implicit-def dead $eflags
+    $edi = COPY killed %3, debug-location !15
+    CALL64pcrel32 @ext, csr_64, implicit $rsp, implicit $ssp, implicit killed $edi, implicit-def $rsp, implicit-def $ssp, implicit-def $eax, debug-location !15
+    ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp, debug-location !15
+    %4:gr32 = COPY killed $eax, debug-location !15
+    %10:gr32 = MOV32ri 0
+    %11:gr32 = MOV32ri 1
+    %12:gr32 = MOV32ri 2
+    %13:gr32 = MOV32ri 3
+    %14:gr32 = MOV32ri 4
+    %15:gr32 = MOV32ri 5
+    %16:gr32 = MOV32ri 6
+    %17:gr32 = MOV32ri 7
+    %18:gr32 = MOV32ri 8
+    %19:gr32 = MOV32ri 9
+    %20:gr32 = MOV32ri 10
+    %21:gr32 = MOV32ri 11
+    %22:gr32 = MOV32ri 12
+    %23:gr32 = MOV32ri 13
+    %24:gr32 = MOV32ri 14
+    TEST32rr killed %4, %4, implicit-def $eflags, debug-location !15
+    JCC_1 %bb.2, 5, implicit killed $eflags, debug-location !17
+    JMP_1 %bb.1, debug-location !17
+
+  bb.1:
+    %30:gr32 = MOV32ri 0
+    %31:gr32 = MOV32ri 1
+    %32:gr32 = MOV32ri 2
+    %33:gr32 = MOV32ri 3
+    %34:gr32 = MOV32ri 4
+    %35:gr32 = MOV32ri 5
+    %36:gr32 = MOV32ri 6
+    %37:gr32 = MOV32ri 7
+    %38:gr32 = MOV32ri 8
+    %39:gr32 = MOV32ri 9
+    %40:gr32 = MOV32ri 10
+    %41:gr32 = MOV32ri 11
+    %42:gr32 = MOV32ri 12
+    %43:gr32 = MOV32ri 13
+    %44:gr32 = MOV32ri 14
+
+    ; CHECK-LABEL: bb.2:
+  bb.2:
+    %0:gr16 = PHI %5, %bb.0, %6, %bb.1, debug-instr-number 1, debug-location !18
+    %50:gr32 = PHI %10, %bb.0, %30, %bb.1, debug-location !18
+    %51:gr32 = PHI %11, %bb.0, %31, %bb.1, debug-location !18
+    %52:gr32 = PHI %12, %bb.0, %32, %bb.1, debug-location !18
+    %53:gr32 = PHI %13, %bb.0, %33, %bb.1, debug-location !18
+    %54:gr32 = PHI %14, %bb.0, %34, %bb.1, debug-location !18
+    %55:gr32 = PHI %15, %bb.0, %35, %bb.1, debug-location !18
+    %56:gr32 = PHI %16, %bb.0, %36, %bb.1, debug-location !18
+    %57:gr32 = PHI %17, %bb.0, %37, %bb.1, debug-location !18
+    %58:gr32 = PHI %18, %bb.0, %38, %bb.1, debug-location !18
+    %59:gr32 = PHI %19, %bb.0, %39, %bb.1, debug-location !18
+    %60:gr32 = PHI %20, %bb.0, %40, %bb.1, debug-location !18
+    %61:gr32 = PHI %21, %bb.0, %41, %bb.1, debug-location !18
+    %62:gr32 = PHI %22, %bb.0, %42, %bb.1, debug-location !18
+    %63:gr32 = PHI %23, %bb.0, %43, %bb.1, debug-location !18
+    %64:gr32 = PHI %24, %bb.0, %44, %bb.1, debug-location !18
+
+    INLINEASM &"", 1, 12, %50, 12, %51, 12, %52, 12, %53, 12, %54, 12, %55, 12, %56, 12, %57, 12, %58, 12, %59, 12, %60, 12, %61, 12, %62, 12, %63, 12, %64
+    DBG_INSTR_REF 1, 0, !14, !DIExpression(), debug-location !12
+    ; CHECK:      DBG_PHI %stack.0, 1, 16
+    ; CHECK:      DBG_INSTR_REF 1, 0
+    ; CHECK:      renamable $eax = MOV32rm %stack.0,
+    $eax = COPY killed %0, debug-location !19
+    RET 0, killed $eax, debug-location !19
+
+...
diff --git a/llvm/test/DebugInfo/MIR/InstrRef/phi-on-stack-coalesced2.mir b/llvm/test/DebugInfo/MIR/InstrRef/phi-on-stack-coalesced2.mir
new file mode 100644
index 000000000000..1047c005a5ad
--- /dev/null
+++ b/llvm/test/DebugInfo/MIR/InstrRef/phi-on-stack-coalesced2.mir
@@ -0,0 +1,155 @@
+# RUN: llc %s -o - -mtriple=x86_64-unknown-unknown \
+# RUN:    -experimental-debug-variable-locations \
+# RUN:    -start-before=phi-node-elimination -stop-after=virtregrewriter \
+# RUN:    | FileCheck %s
+#
+# Pass a PHI node into register allocation, and test that it is correctly
+# dropped.  In this test the desired value is an 8 bit copy of an argument,
+# but it's located in an upper subregister field. That coalesces back to the
+# whole argument, which is spilt to the stack.
+#
+# Currently, DBG_PHIs can't describe non-zero offsets in stack slots, therefore
+# no DBG_PHI should be emitted. (This means there is no value for that
+# instruction/operand number, and any DBG_INSTR_REF will become a
+# DBG_VALUE $noreg.
+
+--- |
+  ; ModuleID = 'promoted.ll'
+  source_filename = "test.c"
+  target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+  target triple = "x86_64-unknown-linux-gnu"
+
+  define dso_local i32 @foo(i32 %bar, i32 %baz) !dbg !7 {
+  entry:
+    ret i32 0, !dbg !19
+  }
+
+  declare dso_local i32 @ext(i32)
+
+  ; Function Attrs: nounwind readnone speculatable willreturn
+  declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+  !llvm.dbg.cu = !{!0}
+  !llvm.module.flags = !{!3, !4, !5}
+  !llvm.ident = !{!6}
+
+  !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
+  !1 = !DIFile(filename: "test.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 = !{!"."}
+  !7 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 2, type: !8, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+  !8 = !DISubroutineType(types: !9)
+  !9 = !{!10, !10, !10}
+  !10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+  !11 = !DILocalVariable(name: "bar", arg: 1, scope: !7, file: !1, line: 2, type: !10)
+  !12 = !DILocation(line: 0, scope: !7)
+  !13 = !DILocalVariable(name: "baz", arg: 2, scope: !7, file: !1, line: 2, type: !10)
+  !14 = !DILocalVariable(name: "either", scope: !7, file: !1, line: 3, type: !10)
+  !15 = !DILocation(line: 4, column: 7, scope: !16)
+  !16 = distinct !DILexicalBlock(scope: !7, file: !1, line: 4, column: 7)
+  !17 = !DILocation(line: 4, column: 7, scope: !7)
+  !18 = !DILocation(line: 0, scope: !16)
+  !19 = !DILocation(line: 9, column: 3, scope: !7)
+
+...
+---
+name:            foo
+alignment:       16
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: gr8 }
+  - { id: 1, class: gr32_abcd }
+  - { id: 2, class: gr32_abcd }
+  - { id: 3, class: gr32 }
+  - { id: 4, class: gr32 }
+liveins:
+  - { reg: '$edi', virtual-reg: '%1' }
+  - { reg: '$esi', virtual-reg: '%2' }
+frameInfo:
+  maxAlignment:    1
+  hasCalls:        true
+machineFunctionInfo: {}
+body:             |
+  bb.0:
+    successors: %bb.2(0x50000000), %bb.1(0x30000000)
+    liveins: $edi, $esi
+
+    DBG_VALUE $edi, $noreg, !11, !DIExpression(), debug-location !12
+    DBG_VALUE $esi, $noreg, !13, !DIExpression(), debug-location !12
+    %2:gr32_abcd = COPY killed $esi
+    %1:gr32_abcd = COPY killed $edi
+    %5:gr8 = COPY %1.sub_8bit_hi
+    %6:gr8 = COPY %1.sub_8bit_hi
+    ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp, debug-location !15
+    %3:gr32 = MOV32r0 implicit-def dead $eflags
+    $edi = COPY killed %3, debug-location !15
+    CALL64pcrel32 @ext, csr_64, implicit $rsp, implicit $ssp, implicit killed $edi, implicit-def $rsp, implicit-def $ssp, implicit-def $eax, debug-location !15
+    ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp, debug-location !15
+    %4:gr32 = COPY killed $eax, debug-location !15
+    %10:gr32 = MOV32ri 0
+    %11:gr32 = MOV32ri 1
+    %12:gr32 = MOV32ri 2
+    %13:gr32 = MOV32ri 3
+    %14:gr32 = MOV32ri 4
+    %15:gr32 = MOV32ri 5
+    %16:gr32 = MOV32ri 6
+    %17:gr32 = MOV32ri 7
+    %18:gr32 = MOV32ri 8
+    %19:gr32 = MOV32ri 9
+    %20:gr32 = MOV32ri 10
+    %21:gr32 = MOV32ri 11
+    %22:gr32 = MOV32ri 12
+    %23:gr32 = MOV32ri 13
+    %24:gr32 = MOV32ri 14
+    TEST32rr killed %4, %4, implicit-def $eflags, debug-location !15
+    JCC_1 %bb.2, 5, implicit killed $eflags, debug-location !17
+    JMP_1 %bb.1, debug-location !17
+
+  bb.1:
+    %30:gr32 = MOV32ri 0
+    %31:gr32 = MOV32ri 1
+    %32:gr32 = MOV32ri 2
+    %33:gr32 = MOV32ri 3
+    %34:gr32 = MOV32ri 4
+    %35:gr32 = MOV32ri 5
+    %36:gr32 = MOV32ri 6
+    %37:gr32 = MOV32ri 7
+    %38:gr32 = MOV32ri 8
+    %39:gr32 = MOV32ri 9
+    %40:gr32 = MOV32ri 10
+    %41:gr32 = MOV32ri 11
+    %42:gr32 = MOV32ri 12
+    %43:gr32 = MOV32ri 13
+    %44:gr32 = MOV32ri 14
+
+    ; CHECK-LABEL: bb.2:
+  bb.2:
+    %0:gr8 = PHI %5, %bb.0, %6, %bb.1, debug-instr-number 1, debug-location !18
+    %50:gr32 = PHI %10, %bb.0, %30, %bb.1, debug-location !18
+    %51:gr32 = PHI %11, %bb.0, %31, %bb.1, debug-location !18
+    %52:gr32 = PHI %12, %bb.0, %32, %bb.1, debug-location !18
+    %53:gr32 = PHI %13, %bb.0, %33, %bb.1, debug-location !18
+    %54:gr32 = PHI %14, %bb.0, %34, %bb.1, debug-location !18
+    %55:gr32 = PHI %15, %bb.0, %35, %bb.1, debug-location !18
+    %56:gr32 = PHI %16, %bb.0, %36, %bb.1, debug-location !18
+    %57:gr32 = PHI %17, %bb.0, %37, %bb.1, debug-location !18
+    %58:gr32 = PHI %18, %bb.0, %38, %bb.1, debug-location !18
+    %59:gr32 = PHI %19, %bb.0, %39, %bb.1, debug-location !18
+    %60:gr32 = PHI %20, %bb.0, %40, %bb.1, debug-location !18
+    %61:gr32 = PHI %21, %bb.0, %41, %bb.1, debug-location !18
+    %62:gr32 = PHI %22, %bb.0, %42, %bb.1, debug-location !18
+    %63:gr32 = PHI %23, %bb.0, %43, %bb.1, debug-location !18
+    %64:gr32 = PHI %24, %bb.0, %44, %bb.1, debug-location !18
+
+    INLINEASM &"", 1, 12, %50, 12, %51, 12, %52, 12, %53, 12, %54, 12, %55, 12, %56, 12, %57, 12, %58, 12, %59, 12, %60, 12, %61, 12, %62, 12, %63, 12, %64
+    DBG_INSTR_REF 1, 0, !14, !DIExpression(), debug-location !12
+    ; CHECK-NOT:  DBG_PHI
+    ; CHECK:      DBG_INSTR_REF 1, 0
+    ; CHECK-NOT:  DBG_PHI
+    $eax = COPY killed %0, debug-location !19
+    RET 0, killed $eax, debug-location !19
+
+...
diff --git a/llvm/test/DebugInfo/MIR/InstrRef/phi-regallocd-to-stack.mir b/llvm/test/DebugInfo/MIR/InstrRef/phi-regallocd-to-stack.mir
index b40f2ae9cb6d..f8733e1128f9 100644
--- a/llvm/test/DebugInfo/MIR/InstrRef/phi-regallocd-to-stack.mir
+++ b/llvm/test/DebugInfo/MIR/InstrRef/phi-regallocd-to-stack.mir
@@ -140,7 +140,7 @@ body:             |
     %64:gr32 = PHI %24, %bb.0, %44, %bb.1, debug-location !18
 
     DBG_INSTR_REF 1, 0, !14, !DIExpression(), debug-location !12
-    ; CHECK:      DBG_PHI %stack.1, 1
+    ; CHECK:      DBG_PHI %stack.1, 1, 32
     ; CHECK:      renamable $eax = MOV32rm %stack.1,
     ; CHECK:      DBG_INSTR_REF 1, 0
     $eax = COPY killed %0, debug-location !19