4 files changed, 26 insertions, 19 deletions
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 71fbfaa567c..151cf3c4247 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1180,6 +1180,18 @@ DwarfDebug::buildLocationList(SmallVectorImpl<DebugLocEntry> &DebugLoc,
     LLVM_DEBUG(dbgs() << "DotDebugLoc: " << *Begin << "\n");
 
     auto Value = getDebugLocValue(Begin);
+
+    // Omit entries with empty ranges as they do not have any effect in DWARF.
+    if (StartLabel == EndLabel) {
+      // If this is a fragment, we must still add the value to the list of
+      // open ranges, since it may describe non-overlapping parts of the
+      // variable.
+      if (DIExpr->isFragment())
+        OpenRanges.push_back(Value);
+      LLVM_DEBUG(dbgs() << "Omitting location list entry with empty range.\n");
+      continue;
+    }
+
     DebugLocEntry Loc(StartLabel, EndLabel, Value);
     bool couldMerge = false;
 
@@ -1918,6 +1930,7 @@ static void emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
 void DebugLocEntry::finalize(const AsmPrinter &AP,
                              DebugLocStream::ListBuilder &List,
                              const DIBasicType *BT) {
+  assert(Begin != End && "unexpected location list entry with empty range");
   DebugLocStream::EntryBuilder Entry(List, Begin, End);
   BufferByteStreamer Streamer = Entry.getStreamer();
   DebugLocDwarfExpression DwarfExpr(AP.getDwarfVersion(), Streamer);
diff --git a/llvm/test/DebugInfo/ARM/PR26163.ll b/llvm/test/DebugInfo/ARM/PR26163.ll
index 3b3ec9c3f4f..f341a83cbc3 100644
--- a/llvm/test/DebugInfo/ARM/PR26163.ll
+++ b/llvm/test/DebugInfo/ARM/PR26163.ll
@@ -1,16 +1,17 @@
 ; RUN: llc -filetype=obj -o - < %s | llvm-dwarfdump -v -debug-info - | FileCheck %s
 ;
-; Checks that we're creating two ranges, one that terminates immediately
-; and one that spans the rest of the function. This isn't necessarily the
-; best thing to do here (and also not necessarily correct, since the first
-; one has a bit_piece), but it is what is currently being emitted, any
-; change here needs to be intentional, so the test is very specific.
+; Checks that we're omitting the first range, as it is empty, and that we're
+; emitting one that spans the rest of the function. In this case, the first
+; range, which we omit, describes 8 bytes of the variable using DW_OP_litX,
+; whereas the second one only describes 4 bytes, so clobbering the whole 8 byte
+; fragment with the 4 bytes fragment isn't necessarily best thing to do here,
+; but it is what is currently being emitted. Any change here needs to be
+; intentional, so the test is very specific.
 ;
 ; CHECK: DW_TAG_inlined_subroutine
 ; CHECK: DW_TAG_variable
 ; CHECK:   DW_AT_location [DW_FORM_sec_offset] ({{.*}}
-; CHECK:      [0x00000004, 0x00000004): DW_OP_lit0, DW_OP_stack_value, DW_OP_piece 0x8
-; CHECK:      [0x00000004, 0x00000014): DW_OP_lit0, DW_OP_stack_value, DW_OP_piece 0x4)
+; CHECK-NEXT: [0x00000004, 0x00000014): DW_OP_lit0, DW_OP_stack_value, DW_OP_piece 0x4)
 
 ; Created form the following test case (PR26163) with
 ; clang -cc1 -triple armv4t--freebsd11.0-gnueabi -emit-obj -debug-info-kind=standalone -O2 -x c test.c
diff --git a/llvm/test/DebugInfo/X86/PR26148.ll b/llvm/test/DebugInfo/X86/PR26148.ll
index 685f2d50371..d5ae2dc2ab2 100644
--- a/llvm/test/DebugInfo/X86/PR26148.ll
+++ b/llvm/test/DebugInfo/X86/PR26148.ll
@@ -16,11 +16,10 @@
 ; This is similar to the bug in test/DebugInfo/ARM/PR26163.ll, except that there is an
 ; extra non-overlapping range first. Thus, we make sure that the backend actually looks
 ; at all expressions when determining whether to merge ranges, not just the first one.
-; AS in 26163, we expect two ranges (as opposed to one), the first one being zero sized
+; AS in 26163, we only expect one range as the first one is zero sized.
 ;
 ;
-; CHECK: [0x0000000000000004, 0x0000000000000004): DW_OP_lit3, DW_OP_piece 0x4, DW_OP_reg5 RDI, DW_OP_piece 0x2
-; CHECK: [0x0000000000000004, 0x0000000000000014): DW_OP_lit3, DW_OP_piece 0x4, DW_OP_lit0, DW_OP_piece 0x4
+; CHECK: [0x0000000000000000, 0x000000000000000f): DW_OP_lit3, DW_OP_piece 0x4, DW_OP_lit0, DW_OP_piece 0x4
 
 source_filename = "test/DebugInfo/X86/PR26148.ll"
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
@@ -35,11 +34,8 @@ declare void @llvm.dbg.declare(metadata, metadata, metadata) #0
 
 ; Function Attrs: nounwind readnone
 declare void @llvm.dbg.value(metadata, metadata, metadata) #0
-; The attributes are here to force the zero-sized range not to be at the start of
-; the function, which has special interpretation in DWARF. The fact that this happens
-; at all is probably an LLVM bug.
 
-define void @fn1(i16 signext %p1) #1 !dbg !16 {
+define void @fn1(i16 signext %p1) !dbg !16 {
 entry:
   tail call void @llvm.dbg.value(metadata i16 %p1, metadata !20, metadata !23), !dbg !24
   tail call void @llvm.dbg.declare(metadata %struct.S0* undef, metadata !21, metadata !23), !dbg !25
@@ -60,7 +56,6 @@ entry:
 }
 
 attributes #0 = { nounwind readnone }
-attributes #1 = { "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" }
 
 !llvm.dbg.cu = !{!2}
 !llvm.module.flags = !{!12, !13, !14}
diff --git a/llvm/test/DebugInfo/X86/pieces-3.ll b/llvm/test/DebugInfo/X86/pieces-3.ll
index 0f705f14f8f..e91bd262e79 100644
--- a/llvm/test/DebugInfo/X86/pieces-3.ll
+++ b/llvm/test/DebugInfo/X86/pieces-3.ll
@@ -18,12 +18,10 @@
 ; CHECK: DW_TAG_formal_parameter [3]
 ; CHECK-NEXT:   DW_AT_location [DW_FORM_data4]        (
 ; CHECK-NEXT:     [0x0000000000000000, 0x0000000000000007): DW_OP_reg5 RDI, DW_OP_piece 0x8, DW_OP_piece 0x4, DW_OP_reg4 RSI, DW_OP_piece 0x4
-; CHECK-NEXT:     [0x0000000000000007, 0x0000000000000007): DW_OP_reg5 RDI, DW_OP_piece 0x8, DW_OP_piece 0x4, DW_OP_reg0 RAX, DW_OP_piece 0x4)
 ; CHECK-NEXT:   DW_AT_name {{.*}}"outer"
 ; CHECK: DW_TAG_variable
-; CHECK-NEXT:   DW_AT_location [DW_FORM_data4]        (0x00000044
-; CHECK-NEXT:     [0x0000000000000007, 0x0000000000000007): DW_OP_reg0 RAX, DW_OP_piece 0x4)
-; CHECK-NEXT:   "i1"
+; CHECK-NEXT:   DW_AT_name {{.*}}"i1"
+; CHECK-NOT:    DW_AT_location
 
 ; ModuleID = '/Volumes/Data/llvm/test/DebugInfo/X86/sroasplit-2.ll'
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"