llvm18/0004-Backport-MC-LoongArch-Add-AlignFragment-size-if-layout-is-available-and-not-need-insert-nops.patch

From be6e5c566f49bee5efe3d710bdd321e15d8d95ea Mon Sep 17 00:00:00 2001
From: Jinyang He <hejinyang@loongson.cn>
Date: Thu, 14 Mar 2024 12:10:50 +0800
Subject: [PATCH 05/14] [MC][LoongArch] Add AlignFragment size if layout is
 available and not need insert nops (#76552)

Due to delayed decision for ADD/SUB relocations, RISCV and LoongArch may
go slow fragment walk path with available layout. When RISCV (or
LoongArch in the future) don't need insert nops, that means relax is
disabled. With available layout and not needing insert nops, the size of
AlignFragment should be a constant. So we can add it to Displacement for
folding A-B.

(cherry picked from commit 0731567a31e4ade97c27801045156a88c4589704)
Change-Id: I554d6766bd7f688204e956e4a6431574b4c511c9
---
 llvm/lib/MC/MCExpr.cpp                        |  6 +++++
 llvm/test/MC/LoongArch/Misc/cfi-advance.s     | 27 +++++++++++++++++++
 .../MC/LoongArch/Relocations/relax-addsub.s   | 17 +++---------
 3 files changed, 37 insertions(+), 13 deletions(-)
 create mode 100644 llvm/test/MC/LoongArch/Misc/cfi-advance.s

diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index 5a6596f93824..a561fed11179 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -707,8 +707,14 @@ static void AttemptToFoldSymbolOffsetDifference(
       }
 
       int64_t Num;
+      unsigned Count;
       if (DF) {
         Displacement += DF->getContents().size();
+      } else if (auto *AF = dyn_cast<MCAlignFragment>(FI);
+                 AF && Layout &&
+                 !Asm->getBackend().shouldInsertExtraNopBytesForCodeAlign(
+                     *AF, Count)) {
+        Displacement += Asm->computeFragmentSize(*Layout, *AF);
       } else if (auto *FF = dyn_cast<MCFillFragment>(FI);
                  FF && FF->getNumValues().evaluateAsAbsolute(Num)) {
         Displacement += Num * FF->getValueSize();
diff --git a/llvm/test/MC/LoongArch/Misc/cfi-advance.s b/llvm/test/MC/LoongArch/Misc/cfi-advance.s
new file mode 100644
index 000000000000..662c43e6bcea
--- /dev/null
+++ b/llvm/test/MC/LoongArch/Misc/cfi-advance.s
@@ -0,0 +1,27 @@
+# RUN: llvm-mc --filetype=obj --triple=loongarch64 -mattr=-relax %s -o %t.o
+# RUN: llvm-readobj -r %t.o | FileCheck --check-prefix=RELOC %s
+# RUN: llvm-dwarfdump --debug-frame %t.o | FileCheck --check-prefix=DWARFDUMP %s
+
+# RELOC:       Relocations [
+# RELOC-NEXT:    .rela.eh_frame {
+# RELOC-NEXT:       0x1C R_LARCH_32_PCREL .text 0x0
+# RELOC-NEXT:    }
+# RELOC-NEXT:  ]
+# DWARFDUMP:       DW_CFA_advance_loc: 4
+# DWARFDUMP-NEXT:  DW_CFA_def_cfa_offset: +8
+# DWARFDUMP-NEXT:  DW_CFA_advance_loc: 8
+# DWARFDUMP-NEXT:  DW_CFA_def_cfa_offset: +8
+
+        .text
+        .globl test
+        .p2align 2
+        .type   test,@function
+test:
+        .cfi_startproc
+        nop
+        .cfi_def_cfa_offset 8
+        .p2align 3
+        nop
+        .cfi_def_cfa_offset 8
+        nop
+        .cfi_endproc
diff --git a/llvm/test/MC/LoongArch/Relocations/relax-addsub.s b/llvm/test/MC/LoongArch/Relocations/relax-addsub.s
index c4454f5bb98d..14922657ae89 100644
--- a/llvm/test/MC/LoongArch/Relocations/relax-addsub.s
+++ b/llvm/test/MC/LoongArch/Relocations/relax-addsub.s
@@ -23,14 +23,6 @@
 # RELAX-NEXT:      0x14 R_LARCH_RELAX - 0x0
 # RELAX-NEXT:    }
 # RELAX-NEXT:    Section ({{.*}}) .rela.data {
-# RELAX-NEXT:      0xF R_LARCH_ADD8 .L3 0x0
-# RELAX-NEXT:      0xF R_LARCH_SUB8 .L2 0x0
-# RELAX-NEXT:      0x10 R_LARCH_ADD16 .L3 0x0
-# RELAX-NEXT:      0x10 R_LARCH_SUB16 .L2 0x0
-# RELAX-NEXT:      0x12 R_LARCH_ADD32 .L3 0x0
-# RELAX-NEXT:      0x12 R_LARCH_SUB32 .L2 0x0
-# RELAX-NEXT:      0x16 R_LARCH_ADD64 .L3 0x0
-# RELAX-NEXT:      0x16 R_LARCH_SUB64 .L2 0x0
 # RELAX-NEXT:      0x1E R_LARCH_ADD8 .L4 0x0
 # RELAX-NEXT:      0x1E R_LARCH_SUB8 .L3 0x0
 # RELAX-NEXT:      0x1F R_LARCH_ADD16 .L4 0x0
@@ -43,8 +35,8 @@
 # RELAX-NEXT:  ]
 
 # RELAX:      Hex dump of section '.data':
-# RELAX-NEXT: 0x00000000 04040004 00000004 00000000 00000000
-# RELAX-NEXT: 0x00000010 00000000 00000000 00000000 00000000
+# RELAX-NEXT: 0x00000000 04040004 00000004 00000000 0000000c
+# RELAX-NEXT: 0x00000010 0c000c00 00000c00 00000000 00000000
 # RELAX-NEXT: 0x00000020 00000000 00000000 00000000 00
 
 .text
@@ -63,13 +55,12 @@
 .short .L2 - .L1
 .word  .L2 - .L1
 .dword .L2 - .L1
-## With relaxation, emit relocs because of the .align making the diff variable.
-## TODO Handle alignment directive. Why they emit relocs now? They returns
-## without folding symbols offset in AttemptToFoldSymbolOffsetDifference().
+## TODO Handle alignment directive.
 .byte  .L3 - .L2
 .short .L3 - .L2
 .word  .L3 - .L2
 .dword .L3 - .L2
+## With relaxation, emit relocs because the la.pcrel makes the diff variable.
 .byte  .L4 - .L3
 .short .L4 - .L3
 .word  .L4 - .L3
-- 
2.20.1