[llvm-branch-commits] [llvm] [dwarf] make dwarf fission compatible with RISCV relaxations 2/2 (PR #164813)
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Wed Nov 5 14:54:47 PST 2025
https://github.com/dlav-sc updated https://github.com/llvm/llvm-project/pull/164813
>From ac224f9079e297ae6b5f675234120d0dcef0ebe8 Mon Sep 17 00:00:00 2001
From: Daniil Avdeev <daniil.avdeev at syntacore.com>
Date: Thu, 18 Sep 2025 02:05:39 +0000
Subject: [PATCH] [dwarf] make dwarf fission compatible with RISCV relaxations
2/2
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.
---
.../CodeGen/AsmPrinter/DwarfCompileUnit.cpp | 8 ++--
llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll | 44 +++++++++++++------
2 files changed, 35 insertions(+), 17 deletions(-)
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 751d3735d3b2b..2e4a26ef70bc2 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/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.
diff --git a/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll b/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll
index f8ab7fc5ad900..64f83ba1a7d7f 100644
--- a/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll
+++ b/llvm/test/DebugInfo/RISCV/relax_dwo_ranges.ll
@@ -1,12 +1,13 @@
; RUN: llc -dwarf-version=5 -split-dwarf-file=foo.dwo -O0 %s -mtriple=riscv64-unknown-linux-gnu -filetype=obj -o %t
; RUN: llvm-dwarfdump -v %t | FileCheck --check-prefix=DWARF5 %s
; RUN: llvm-dwarfdump --debug-info %t 2> %t.txt
-; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --implicit-check-not=warning:
+; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --allow-empty --implicit-check-not=warning:
; RUN: llc -dwarf-version=4 -split-dwarf-file=foo.dwo -O0 %s -mtriple=riscv64-unknown-linux-gnu -filetype=obj -o %t
; RUN: llvm-dwarfdump -v %t | FileCheck --check-prefix=DWARF4 %s
; RUN: llvm-dwarfdump --debug-info %t 2> %t.txt
-; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --implicit-check-not=warning:
+; RUN: FileCheck --input-file=%t.txt %s --check-prefix=RELOCS --allow-empty --implicit-check-not=warning:
+; RUN: llvm-objdump -h %t | FileCheck --check-prefix=HDR %s
; In the RISC-V architecture, the .text section is subject to
; relaxation, meaning the start address of each function can change
@@ -49,60 +50,75 @@
; clang -g -S -gsplit-dwarf --target=riscv64 -march=rv64gc -O0 relax_dwo_ranges.cpp
-; 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'
+; RELOCS-NOT: 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-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 = 0x0000000000000044 ".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: 0x0000000000000044
; DWARF5-NEXT: 0x0000000000000046
; DWARF5-NEXT: 0x000000000000006c
; DWARF5-NEXT: 0x00000000000000b0
; 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, 0x0000000000000024 => [0x0000000000000046, 0x000000000000006a)
+; DWARF5-NEXT: 0x00000014: [DW_RLE_startx_length]: 0x0000000000000002, 0x0000000000000024 => [0x0000000000000046, 0x000000000000006a)
; DWARF5-NEXT: 0x00000017: [DW_RLE_end_of_list ]
-; DWARF5-NEXT: 0x00000018: [DW_RLE_startx_endx ]: 0x0000000000000002, 0x0000000000000003 => [0x000000000000006c, 0x00000000000000b0)
+; DWARF5-NEXT: 0x00000018: [DW_RLE_startx_endx ]: 0x0000000000000003, 0x0000000000000004 => [0x000000000000006c, 0x00000000000000b0)
; 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-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 = 0x0000000000000044 ".text")
; DWARF4: DW_AT_name {{.*}} "square")
; DWARF4: DW_TAG_subprogram
-; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000001) address = 0x0000000000000046 ".text")
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000002) address = 0x0000000000000046 ".text")
; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000024)
; DWARF4: DW_AT_name {{.*}} "boo")
; DWARF4: DW_TAG_subprogram
-; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000002) address = 0x000000000000006c ".text")
-; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_data4] (0x00000000)
+; DWARF4-NEXT: DW_AT_low_pc [DW_FORM_GNU_addr_index] (indexed (00000003) address = 0x000000000000006c ".text")
+; DWARF4-NEXT: DW_AT_high_pc [DW_FORM_GNU_addr_index] (indexed (00000004) address = 0x00000000000000b0 ".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: 0x0000000000000044
; DWARF4-NEXT: 0x0000000000000046
; DWARF4-NEXT: 0x000000000000006c
+; DWARF4-NEXT: 0x00000000000000b0
; DWARF4-NEXT: ]
+; HDR-NOT: .rela.{{.*}}.dwo
+
; Function Attrs: mustprogress noinline optnone
define dso_local noundef signext i32 @_Z6squarei(i32 noundef signext %0) #0 !dbg !11 {
%2 = alloca i32, align 4
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