Automerge: [dwarf] make dwarf fission compatible with RISCV relaxations 2/2 (#164813)

This patch makes DWARF fission compatible with RISC-V relaxations by
using indirect addressing for the DW_AT_high_pc attribute. This
eliminates the remaining relocations in .dwo files.

Author: daniilavdeev

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -493,10 +493,12 @@ void DwarfCompileUnit::attachLowHighPC(DIE &D, const MCSymbol *Begin,
   assert(End->isDefined() && "Invalid end label");
 
   addLabelAddress(D, dwarf::DW_AT_low_pc, Begin);
-  if (DD->getDwarfVersion() < 4)
-    addLabelAddress(D, dwarf::DW_AT_high_pc, End);
-  else
+  if (DD->getDwarfVersion() >= 4 &&
+      (!isDwoUnit() || !llvm::isRangeRelaxable(Begin, End))) {
     addLabelDelta(D, dwarf::DW_AT_high_pc, End, Begin);
+    return;
+  }
+  addLabelAddress(D, dwarf::DW_AT_high_pc, End);
 }
 
 // Add info for Wasm-global-based relocation.

llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll

@@ -20,68 +20,81 @@
 
 ; RUN: llc -dwarf-version=5 -split-dwarf-file=foo.dwo -O0 -mtriple=riscv64-unknown-linux-gnu -filetype=obj relax_dwo_ranges.ll -o %t.o
 ; RUN: llvm-dwarfdump -v %t.o | FileCheck --check-prefix=DWARF5 %s
-; RUN: llvm-dwarfdump --debug-info %t.o 2> %t.txt
-; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --implicit-check-not=warning:
+; RUN: llvm-dwarfdump --debug-info %t.o > /dev/null 2>&1 | count 0
+; RUN: llvm-objdump -h %t.o | FileCheck --check-prefix=HDR %s
 
 ; RUN: llc -dwarf-version=4 -split-dwarf-file=foo.dwo -O0 -mtriple=riscv64-unknown-linux-gnu -filetype=obj relax_dwo_ranges.ll -o %t.o
 ; RUN: llvm-dwarfdump -v %t.o | FileCheck --check-prefix=DWARF4 %s
-; RUN: llvm-dwarfdump --debug-info %t.o 2> %t.txt
-; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --implicit-check-not=warning:
+; RUN: llvm-dwarfdump --debug-info %t.o > /dev/null 2>&1 | count 0
+; RUN: llvm-objdump -h %t.o | FileCheck --check-prefix=HDR %s
 
-; Currently, square() still uses an offset to represent the function's end address,
-; which requires a relocation here.
-; RELOCS: warning: unexpected relocations for dwo section '.debug_info.dwo'
+; Make sure we don't produce any relocations in any .dwo section
+; HDR-NOT: .rela.{{.*}}.dwo
 
+; Ensure that 'square()' function uses indexed start and end addresses
 ; DWARF5: .debug_info.dwo contents:
 ; DWARF5: DW_TAG_subprogram
-; DWARF5-NEXT: DW_AT_low_pc [DW_FORM_addrx]    (indexed (00000000) address = 0x0000000000000000 ".text")
-; DWARF5-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000000)
-; DWARF5: DW_AT_name {{.*}} "square")
+; DWARF5-NEXT: DW_AT_low_pc  [DW_FORM_addrx]    (indexed (00000000) address = 0x0000000000000000 ".text")
+; DWARF5-NEXT: DW_AT_high_pc [DW_FORM_addrx]    (indexed (00000001) address = 0x000000000000002c ".text")
+; DWARF5: DW_AT_name {{.*}} "square") 
 ; DWARF5: DW_TAG_formal_parameter
 
+; HDR-NOT: .rela.{{.*}}.dwo
+
 ; Ensure there is no unnecessary addresses in .o file
 ; DWARF5: .debug_addr contents:
 ; DWARF5: Addrs: [
 ; DWARF5-NEXT: 0x0000000000000000
 ; DWARF5-NEXT: 0x000000000000002c
+; DWARF5-NEXT: 0x000000000000002c
 ; DWARF5-NEXT: 0x000000000000003e
 ; DWARF5-NEXT: 0x000000000000006e
 ; DWARF5-NEXT: ]
 
+; HDR-NOT: .rela.{{.*}}.dwo
+
 ; Ensure that 'boo()' and 'main()' use DW_RLE_startx_length and DW_RLE_startx_endx
 ; entries respectively
 ; DWARF5: .debug_rnglists.dwo contents:
 ; DWARF5: ranges:
-; DWARF5-NEXT: 0x00000014: [DW_RLE_startx_length]:  0x0000000000000001, 0x0000000000000012 => [0x000000000000002c, 0x000000000000003e)
+; DWARF5-NEXT: 0x00000014: [DW_RLE_startx_length]:  0x0000000000000002, 0x0000000000000012 => [0x000000000000002c, 0x000000000000003e)
 ; DWARF5-NEXT: 0x00000017: [DW_RLE_end_of_list  ]
-; DWARF5-NEXT: 0x00000018: [DW_RLE_startx_endx  ]:  0x0000000000000002, 0x0000000000000003 => [0x000000000000003e, 0x000000000000006e)
+; DWARF5-NEXT: 0x00000018: [DW_RLE_startx_endx  ]:  0x0000000000000003, 0x0000000000000004 => [0x000000000000003e, 0x000000000000006e)
 ; DWARF5-NEXT: 0x0000001b: [DW_RLE_end_of_list  ]
 ; DWARF5-EMPTY:
 
+; HDR-NOT: .rela.{{.*}}.dwo
+
 ; DWARF4: .debug_info.dwo contents:
 ; DWARF4: DW_TAG_subprogram
-; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index]	(indexed (00000000) address = 0x0000000000000000 ".text")
-; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4]	(0x00000000)
-; DWARF4: DW_AT_name {{.*}} "square")
+; DWARF4-NEXT: DW_AT_low_pc  [DW_FORM_GNU_addr_index]	(indexed (00000000) address = 0x0000000000000000 ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_GNU_addr_index] (indexed (00000001) address = 0x000000000000002c ".text")
+; DWARF4: DW_AT_name {{.*}} "square") 
 
 ; DWARF4: DW_TAG_subprogram
-; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index]	(indexed (00000001) address = 0x000000000000002c ".text")
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index]	(indexed (00000002) address = 0x000000000000002c ".text")
 ; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4]	(0x00000012)
-; DWARF4: DW_AT_name {{.*}} "boo")
+; DWARF4: DW_AT_name {{.*}} "boo") 
 
 ; DWARF4: DW_TAG_subprogram
-; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index]	(indexed (00000002) address = 0x000000000000003e ".text")
-; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4]	(0x00000000)
-; DWARF4: DW_AT_name {{.*}} "main")
+; DWARF4-NEXT: DW_AT_low_pc  [DW_FORM_GNU_addr_index] (indexed (00000003) address = 0x000000000000003e ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_GNU_addr_index] (indexed (00000004) address = 0x000000000000006e ".text")
+; DWARF4: DW_AT_name {{.*}} "main") 
+
+; HDR-NOT: .rela.{{.*}}.dwo
 
 ; Ensure there is no unnecessary addresses in .o file
 ; DWARF4: .debug_addr contents:
 ; DWARF4: Addrs: [
 ; DWARF4-NEXT: 0x0000000000000000
 ; DWARF4-NEXT: 0x000000000000002c
+; DWARF4-NEXT: 0x000000000000002c
 ; DWARF4-NEXT: 0x000000000000003e
+; DWARF4-NEXT: 0x000000000000006e
 ; DWARF4-NEXT: ]
 
+; HDR-NOT: .rela.{{.*}}.dwo
+
 #--- relax_dwo_ranges.cpp
 __attribute__((noinline)) int boo();