[llvm] 86caa03 - Revert "Round up zero-sized symbols to 1 byte in `.debug_aranges`."

[Bjorn Pettersson via llvm-commits]

Author: Bjorn Pettersson
Date: 2022-05-31T11:03:44+02:00
New Revision: 86caa0371859d450ed60c4b186d8ccbcc72fef5e

URL: https://github.com/llvm/llvm-project/commit/86caa0371859d450ed60c4b186d8ccbcc72fef5e
DIFF: https://github.com/llvm/llvm-project/commit/86caa0371859d450ed60c4b186d8ccbcc72fef5e.diff

LOG: Revert "Round up zero-sized symbols to 1 byte in `.debug_aranges`."

This reverts commit 256a52d9aac8a9e98fbfd6a3d91090bf127cef7d (and
also the follow-up commit 38eb4fe74b3843ab0d7fc1e that moved a test
case to a different directory).

As discussed in https://reviews.llvm.org/D126257 there is a suspicion
that something was wrong with this commit as text section range was
shortened to 1 byte rather than rounded up as shown in the
llvm/test/DebugInfo/X86/dwarf-aranges.ll test case.

Added: 
    

Modified: 
    llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
    llvm/test/DebugInfo/MSP430/dwarf-basics-v5.ll
    llvm/test/DebugInfo/X86/dwarf-aranges.ll

Removed: 
    llvm/test/CodeGen/X86/dwarf-aranges-zero-size.ll


################################################################################
diff  --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 50032c887d839..37ae84ad9bf17 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -3042,17 +3042,13 @@ void DwarfDebug::emitDebugARanges() {
     for (const ArangeSpan &Span : List) {
       Asm->emitLabelReference(Span.Start, PtrSize);
 
-      // Calculate the size as being from the span start to its end.
-      //
-      // If the size is zero, then round it up to one byte. The DWARF
-      // specification requires that entries in this table have nonzero
-      // lengths.
-      uint64_t Size = SymSize[Span.Start];
-      if (Size != 0 && Span.End) {
+      // Calculate the size as being from the span start to it's end.
+      if (Span.End) {
         Asm->emitLabelDifference(Span.End, Span.Start, PtrSize);
       } else {
         // For symbols without an end marker (e.g. common), we
         // write a single arange entry containing just that one symbol.
+        uint64_t Size = SymSize[Span.Start];
         if (Size == 0)
           Size = 1;
 

diff  --git a/llvm/test/CodeGen/X86/dwarf-aranges-zero-size.ll b/llvm/test/CodeGen/X86/dwarf-aranges-zero-size.ll
deleted file mode 100644
index 9a8be3c8f91d2..0000000000000
--- a/llvm/test/CodeGen/X86/dwarf-aranges-zero-size.ll
+++ /dev/null
@@ -1,23 +0,0 @@
-; Ensures that the AsmPrinter doesn't emit zero-sized symbols into `.debug_aranges`.
-;
-; RUN: llc --generate-arange-section < %s | FileCheck %s
-; CHECK: .section .debug_aranges
-; CHECK: .quad EXAMPLE
-; CHECK-NEXT: .quad 1
-; CHECK: .section
-
-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"
-
- at EXAMPLE = constant <{ [0 x i8] }> zeroinitializer, align 1, !dbg !0
-
-!llvm.module.flags = !{!3}
-!llvm.dbg.cu = !{!4}
-
-!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
-!1 = distinct !DIGlobalVariable(name: "EXAMPLE", linkageName: "EXAMPLE", scope: null, file: null, line: 161, type: !2, isLocal: false, isDefinition: true, align: 1)
-!2 = !DIBasicType(name: "()", encoding: DW_ATE_unsigned)
-!3 = !{i32 2, !"Debug Info Version", i32 3}
-!4 = distinct !DICompileUnit(language: DW_LANG_Rust, file: !5, producer: "rustc", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: null, globals: !6)
-!5 = !DIFile(filename: "foo", directory: "")
-!6 = !{!0}

diff  --git a/llvm/test/DebugInfo/MSP430/dwarf-basics-v5.ll b/llvm/test/DebugInfo/MSP430/dwarf-basics-v5.ll
index 51d2c4a20589b..98922f1b7d088 100644
--- a/llvm/test/DebugInfo/MSP430/dwarf-basics-v5.ll
+++ b/llvm/test/DebugInfo/MSP430/dwarf-basics-v5.ll
@@ -98,7 +98,7 @@
 
 ; CHECK:      .debug_aranges contents:
 ; CHECK-NEXT: Address Range Header: length = 0x{{.*}}, format = DWARF32, version = 0x0002, cu_offset = 0x00000000, addr_size = 0x02, seg_size = 0x00
-; CHECK-NEXT: [0x0000, 0x0001)
+; CHECK-NEXT: [0x0000, 0x0006)
 
 ; CHECK:      .debug_addr contents:
 ; CHECK-NEXT: Address table header: length = 0x{{.*}}, format = DWARF32, version = 0x0005, addr_size = 0x02, seg_size = 0x00

diff  --git a/llvm/test/DebugInfo/X86/dwarf-aranges.ll b/llvm/test/DebugInfo/X86/dwarf-aranges.ll
index c43e9eea8b710..5358a30c6a06a 100644
--- a/llvm/test/DebugInfo/X86/dwarf-aranges.ll
+++ b/llvm/test/DebugInfo/X86/dwarf-aranges.ll
@@ -22,7 +22,7 @@
 
 ; <text section> - it should have made one span covering all functions in this CU.
 ; CHECK-NEXT: .quad .Lfunc_begin0
-; CHECK-NEXT: .quad 1
+; CHECK-NEXT: .quad .Lsec_end2-.Lfunc_begin0
 
 ; -- finish --
 ; CHECK-NEXT: # ARange terminator