backport D101773 to fix an llvm ir issue on mipsel in mips/mips-D101773-reloc.patch (Closes: #988965)

debian/changelog

@@ -1,3 +1,15 @@
+llvm-toolchain-12 (1:12.0.1~++20210528111127+328a6ec95532-1~exp1) UNRELEASED; urgency=medium
+
+  * experimental New snapshot release
+
+ -- Sylvestre Ledru <sylvestre@debian.org>  Fri, 28 May 2021 23:14:58 +0200
+
+llvm-toolchain-12 (1:12.0.1-rc1) unstable; urgency=medium
+
+  * New testing upstream release
+
+ -- Sylvestre Ledru <sylvestre@debian.org>  Wed, 26 May 2021 12:45:40 +0200
+
 llvm-toolchain-12 (1:12.0.1~+rc1-1~exp2) UNRELEASED; urgency=medium
 
   [ John Paul Adrian Glaubitz ]
@@ -8,6 +20,10 @@ llvm-toolchain-12 (1:12.0.1~+rc1-1~exp2) UNRELEASED; urgency=medium
   * Add -fvisibility-inlines-hidden -Bsymbolic-functions -fno-semantic-interposition
     to the args to make clang faster
     See https://github.com/ClangBuiltLinux/tc-build/issues/150#issuecomment-849935207
+  * backport D101773 to fix an llvm ir issue on mipsel
+    in mips/mips-D101773-reloc.patch
+    thanks to Ximin Luo
+    (Closes: #988965)
 
  -- Sylvestre Ledru <sylvestre@debian.org>  Fri, 28 May 2021 10:53:08 +0200
 

debian/patches/mips/mips-D101773-reloc.patch

@@ -0,0 +1,75 @@
+From ab40c027f0ce9492919a72ad339de40bdb84b354 Mon Sep 17 00:00:00 2001
+From: Dimitry Andric <dimitry@andric.com>
+Date: Mon, 3 May 2021 20:08:49 +0200
+Subject: [PATCH] [MC][ELF] Work around R_MIPS_LO16 relocation handling problem
+
+This fixes PR49821, and avoids "ld.lld: error: test.o:(.rodata.str1.1):
+offset is outside the section" errors when linking MIPS objects with
+negative R_MIPS_LO16 implicit addends.
+
+ld.lld handles R_MIPS_HI16/R_MIPS_LO16 separately, not as a whole, so it
+doesn't know that an R_MIPS_HI16 with implicit addend 1 and an
+R_MIPS_LO16 with implicit addend -32768 represents 32768, which is in
+range of a MergeInputSection. We could introduce a new RelExpr member
+(like R_RISCV_PC_INDIRECT for R_RISCV_PCREL_HI20 / R_RISCV_PCREL_LO12)
+but the complexity is unnecessary given that GNU as keeps the original
+symbol for this case as well.
+
+Reviewed By: atanasyan, MaskRay
+
+Differential Revision: https://reviews.llvm.org/D101773
+---
+ llvm/lib/MC/ELFObjectWriter.cpp | 11 +++++++++++
+ llvm/test/MC/Mips/mips_lo16.s   | 22 ++++++++++++++++++++++
+ 2 files changed, 33 insertions(+)
+ create mode 100644 llvm/test/MC/Mips/mips_lo16.s
+
+Index: llvm-toolchain-12_12.0.1~+rc1/llvm/lib/MC/ELFObjectWriter.cpp
+===================================================================
+--- llvm-toolchain-12_12.0.1~+rc1.orig/llvm/lib/MC/ELFObjectWriter.cpp
++++ llvm-toolchain-12_12.0.1~+rc1/llvm/lib/MC/ELFObjectWriter.cpp
+@@ -1397,6 +1397,17 @@ bool ELFObjectWriter::shouldRelocateWith
+       if (TargetObjectWriter->getEMachine() == ELF::EM_386 &&
+           Type == ELF::R_386_GOTOFF)
+         return true;
++
++      // ld.lld handles R_MIPS_HI16/R_MIPS_LO16 separately, not as a whole, so
++      // it doesn't know that an R_MIPS_HI16 with implicit addend 1 and an
++      // R_MIPS_LO16 with implicit addend -32768 represents 32768, which is in
++      // range of a MergeInputSection. We could introduce a new RelExpr member
++      // (like R_RISCV_PC_INDIRECT for R_RISCV_PCREL_HI20 / R_RISCV_PCREL_LO12)
++      // but the complexity is unnecessary given that GNU as keeps the original
++      // symbol for this case as well.
++      if (TargetObjectWriter->getEMachine() == ELF::EM_MIPS &&
++          !hasRelocationAddend())
++        return true;
+     }
+ 
+     // Most TLS relocations use a got, so they need the symbol. Even those that
+Index: llvm-toolchain-12_12.0.1~+rc1/llvm/test/MC/Mips/mips_lo16.s
+===================================================================
+--- /dev/null
++++ llvm-toolchain-12_12.0.1~+rc1/llvm/test/MC/Mips/mips_lo16.s
+@@ -0,0 +1,22 @@
++# PR49821: Check that R_MIPS_LO16 relocs do not wrap around with large addends.
++
++# RUN: llvm-mc %s -triple mips-unknown-unknown -filetype=obj | \
++# RUN:	 llvm-objdump -d -r --no-show-raw-insn - | \
++# RUN:   FileCheck -check-prefix=MIPS32 %s
++
++# RUN: llvm-mc %s -triple mips64-unknown-unknown -filetype=obj | \
++# RUN:	 llvm-objdump -d -r --no-show-raw-insn - | \
++# RUN:   FileCheck -check-prefix=MIPS64 %s
++
++	.text
++foo:
++	lui	$2, %hi(bar)
++# MIPS32: 00000000:  R_MIPS_HI16  bar
++# MIPS64: 0000000000000000:  R_MIPS_HI16/R_MIPS_NONE/R_MIPS_NONE	.rodata.str1.1+0x8000
++	addiu	$2, $2, %lo(bar)
++# MIPS32: 00000004:  R_MIPS_LO16  bar
++# MIPS64: 0000000000000004:  R_MIPS_LO16/R_MIPS_NONE/R_MIPS_NONE	.rodata.str1.1+0x8000
++	.section	.rodata.str1.1,"aMS",@progbits,1
++	.zero 0x8000
++bar:
++	.asciz	"hello"

debian/patches/series

@@ -83,6 +83,7 @@ libcxx/libcxx-silent-failure-arm64.diff
 # Change default optims
 mips/mips-fpxx-enable.diff
 mips/mips-force-nomadd4.patch
+mips/mips-D101773-reloc.patch
 
 26-set-correct-float-abi.diff
 clang-baseline-fix-i386.patch