From b922004ea29d54534c4f09b9cfa655bf5f3360f0 Mon Sep 17 00:00:00 2001
From: Fangrui Song <i@maskray.me>
Date: Fri, 17 Jul 2020 23:29:50 -0700
Subject: [PATCH] [RelocationResolver] Support R_PPC_REL32 & R_PPC64_REL{32,64}

This suppresses `failed to compute relocation: R_PPC_REL32, Invalid data was encountered while parsing the file`
and its 64-bit variants when running llvm-dwarfdump on a PowerPC object file with .eh_frame

Unfortunately it is difficult to test the computation:
DWARFDataExtractor::getEncodedPointer does not use the relocated value
and even if it does, we need to teach llvm-dwarfdump --eh-frame to do
some linker job to report a reasonable address.
---
 llvm/lib/Object/RelocationResolver.cpp  | 20 +++++++++++++++--
 llvm/test/DebugInfo/PowerPC/eh-frame.ll | 39 +++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 2 deletions(-)
 create mode 100644 llvm/test/DebugInfo/PowerPC/eh-frame.ll

diff --git a/llvm/lib/Object/RelocationResolver.cpp b/llvm/lib/Object/RelocationResolver.cpp
index 9391765..77df7fd 100644
--- a/llvm/lib/Object/RelocationResolver.cpp
+++ b/llvm/lib/Object/RelocationResolver.cpp
@@ -152,6 +152,8 @@ static bool supportsPPC64(uint64_t Type) {
   switch (Type) {
   case ELF::R_PPC64_ADDR32:
   case ELF::R_PPC64_ADDR64:
+  case ELF::R_PPC64_REL32:
+  case ELF::R_PPC64_REL64:
     return true;
   default:
     return false;
@@ -164,6 +166,10 @@ static uint64_t resolvePPC64(RelocationRef R, uint64_t S, uint64_t A) {
     return (S + getELFAddend(R)) & 0xFFFFFFFF;
   case ELF::R_PPC64_ADDR64:
     return S + getELFAddend(R);
+  case ELF::R_PPC64_REL32:
+    return (S + getELFAddend(R) - R.getOffset()) & 0xFFFFFFFF;
+  case ELF::R_PPC64_REL64:
+    return S + getELFAddend(R) - R.getOffset();
   default:
     llvm_unreachable("Invalid relocation type");
   }
@@ -259,12 +265,22 @@ static uint64_t resolveX86(RelocationRef R, uint64_t S, uint64_t A) {
 }
 
 static bool supportsPPC32(uint64_t Type) {
-  return Type == ELF::R_PPC_ADDR32;
+  switch (Type) {
+  case ELF::R_PPC_ADDR32:
+  case ELF::R_PPC_REL32:
+    return true;
+  default:
+    return false;
+  }
 }
 
 static uint64_t resolvePPC32(RelocationRef R, uint64_t S, uint64_t A) {
-  if (R.getType() == ELF::R_PPC_ADDR32)
+  switch (R.getType()) {
+  case ELF::R_PPC_ADDR32:
     return (S + getELFAddend(R)) & 0xFFFFFFFF;
+  case ELF::R_PPC_REL32:
+    return (S + getELFAddend(R) - R.getOffset()) & 0xFFFFFFFF;
+  }
   llvm_unreachable("Invalid relocation type");
 }
 
diff --git a/llvm/test/DebugInfo/PowerPC/eh-frame.ll b/llvm/test/DebugInfo/PowerPC/eh-frame.ll
new file mode 100644
index 0000000..3a8f7df
--- /dev/null
+++ b/llvm/test/DebugInfo/PowerPC/eh-frame.ll
@@ -0,0 +1,39 @@
+; RUN: llc -filetype=obj -mtriple=powerpc %s -o %t32.o
+; RUN: llvm-readobj -r %t32.o | FileCheck %s --check-prefix=PPC_REL
+; RUN: llvm-dwarfdump --eh-frame %t32.o 2>&1 | FileCheck %s --check-prefix=PPC
+
+; PPC_REL:      R_PPC_REL32 .text 0x0
+; PPC_REL-NEXT: R_PPC_REL32 .text 0x4
+
+; PPC-NOT: warning:
+; PPC: FDE cie=00000000 pc=00000000...00000004
+;; TODO Take relocation into consideration
+; PPC: FDE cie=00000000 pc=00000000...00000004
+
+; RUN: llc -filetype=obj -mtriple=ppc64 %s -o %t64.o
+; RUN: llvm-readobj -r %t64.o | FileCheck %s --check-prefix=PPC64_REL
+; RUN: llvm-dwarfdump --eh-frame %t64.o 2>&1 | FileCheck %s --check-prefix=PPC64
+
+; PPC64_REL:      R_PPC64_REL32 .text 0x0
+; PPC64_REL-NEXT: R_PPC64_REL32 .text 0x10
+
+; PPC64-NOT: warning:
+; PPC64: FDE cie=00000000 pc=00000000...00000010
+; PPC64: FDE cie=00000000 pc=00000000...00000010
+
+; RUN: llc -filetype=obj -mtriple=ppc64le -code-model=large %s -o %t64l.o
+; RUN: llvm-readobj -r %t64l.o | FileCheck %s --check-prefix=PPC64L_REL
+; RUN: llvm-dwarfdump --eh-frame %t64l.o 2>&1 | FileCheck %s --check-prefix=PPC64
+
+; PPC64L_REL:      R_PPC64_REL64 .text 0x0
+; PPC64L_REL-NEXT: R_PPC64_REL64 .text 0x10
+
+define void @foo() {
+entry:
+  ret void
+}
+
+define void @bar() {
+entry:
+  ret void
+}
-- 
2.7.4