From fb54afbcb8f460c5c4cafa605259ba0dd77504dc Mon Sep 17 00:00:00 2001
From: Akira Hatanaka <ahatanaka@mips.com>
Date: Wed, 21 Mar 2012 00:52:01 +0000
Subject: [PATCH] Incremental big endian patch by Jack Carter.

These changes allow us to compile big endian from the command line for 32 bit
Mips targets. This patch will result in code and data actually being produced
in the correct endianess.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153153 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Mips/MCTargetDesc/MipsAsmBackend.cpp      | 37 ++++++++++-----
 .../Mips/MCTargetDesc/MipsMCCodeEmitter.cpp   |  6 +--
 test/MC/Mips/elf-bigendian.ll                 | 45 +++++++++++++++++++
 3 files changed, 75 insertions(+), 13 deletions(-)
 create mode 100644 test/MC/Mips/elf-bigendian.ll

diff --git a/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp b/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
index d69570bdf09..7f5c3775b0f 100644
--- a/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
+++ b/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
@@ -92,25 +92,42 @@ public:
     if (!Value)
       return; // Doesn't change encoding.
 
+    // Where do we start in the object
     unsigned Offset = Fixup.getOffset();
-    // FIXME: The below code will not work across endian models
-    // How many bytes/bits are we fixing up?
-    unsigned NumBytes = ((getFixupKindInfo(Kind).TargetSize-1)/8)+1;
-    uint64_t Mask = ((uint64_t)1 << getFixupKindInfo(Kind).TargetSize) - 1;
+    // Number of bytes we need to fixup
+    unsigned NumBytes = (getFixupKindInfo(Kind).TargetSize + 7) / 8;
+    // Used to point to big endian bytes
+    unsigned FullSize;
+
+    switch (Kind) {
+    case Mips::fixup_Mips_16:
+      FullSize = 2;
+      break;
+    case Mips::fixup_Mips_64:
+      FullSize = 8;
+      break;
+    default:
+      FullSize = 4;
+      break;
+    }
 
     // Grab current value, if any, from bits.
     uint64_t CurVal = 0;
-    for (unsigned i = 0; i != NumBytes; ++i)
-      CurVal |= ((uint8_t)Data[Offset + i]) << (i * 8);
 
+    for (unsigned i = 0; i != NumBytes; ++i) {
+      unsigned Idx = IsLittle ? i : (FullSize - 1 - i);
+      CurVal |= (uint64_t)((uint8_t)Data[Offset + Idx]) << (i*8);
+    }
+
+    uint64_t Mask = ((uint64_t)(-1) >> (64 - getFixupKindInfo(Kind).TargetSize));
     CurVal = (CurVal & ~Mask) | ((CurVal + Value) & Mask);
 
-    // Write out the bytes back to the code/data bits.
-    // First the unaffected bits and then the fixup.
+    // Write out the fixed up bytes back to the code/data bits.
     for (unsigned i = 0; i != NumBytes; ++i) {
-      Data[Offset + i] = uint8_t((CurVal >> (i * 8)) & 0xff);
+      unsigned Idx = IsLittle ? i : (FullSize - 1 - i);
+      Data[Offset + Idx] = (uint8_t)((CurVal >> (i*8)) & 0xff);
     }
-}
+  }
 
   unsigned getNumFixupKinds() const { return Mips::NumTargetFixupKinds; }
 
diff --git a/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp b/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
index b0396781750..9ebb6d25690 100644
--- a/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
+++ b/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
@@ -49,9 +49,9 @@ public:
 
   void EmitInstruction(uint64_t Val, unsigned Size, raw_ostream &OS) const {
     // Output the instruction encoding in little endian byte order.
-    for (unsigned i = 0; i != Size; ++i) {
-      EmitByte(Val & 255, OS);
-      Val >>= 8;
+    for (unsigned i = 0; i < Size; ++i) {
+      unsigned Shift = IsLittleEndian ? i * 8 : (Size - 1 - i) * 8;
+      EmitByte((Val >> Shift) & 0xff, OS);
     }
   }
 
diff --git a/test/MC/Mips/elf-bigendian.ll b/test/MC/Mips/elf-bigendian.ll
new file mode 100644
index 00000000000..875ba3ba965
--- /dev/null
+++ b/test/MC/Mips/elf-bigendian.ll
@@ -0,0 +1,45 @@
+; RUN: llc -filetype=obj -mtriple mips-unknown-linux %s -o - | elf-dump --dump-section-data  | FileCheck %s
+
+; Check that this is big endian.
+; CHECK: ('e_indent[EI_DATA]', 0x02)
+
+; Make sure that a section table (text) entry is correct.
+; CHECK:   (('sh_name', 0x{{[0]*}}5) # '.text'
+; CHECKNEXT:   ('sh_type', 0x{{[0]*}}1)
+; CHECKNEXT:   ('sh_flags', 0x{{[0]*}}6)
+; CHECKNEXT:   ('sh_addr', 0x{{{[0-9,a-f]+}})
+; CHECKNEXT:   ('sh_offset', 0x{{{[0-9,a-f]+}})
+; CHECKNEXT:   ('sh_size', 0x{{{[0-9,a-f]+}})
+; CHECKNEXT:   ('sh_link', 0x{{[0]+}})
+; CHECKNEXT:   ('sh_info', 0x{{[0]+}})
+; CHECKNEXT:   ('sh_addralign', 0x{{[0]*}}4)
+; CHECKNEXT:   ('sh_entsize', 0x{{[0]+}})
+
+; See that at least first 3 instructions are correct: GP prologue
+; CHECKNEXT:   ('_section_data', '3c1c0000 279c0000 0399e021 {{[0-9,a-f]*}}')
+
+; ModuleID = '../br1.c'
+target datalayout = "E-p:32:32:32-i1:8:8-i8:8:32-i16:16:32-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-n32"
+target triple = "mips-unknown-linux"
+
+@x = global i32 1, align 4
+@str = private unnamed_addr constant [4 x i8] c"goo\00"
+@str2 = private unnamed_addr constant [4 x i8] c"foo\00"
+
+define i32 @main() nounwind {
+entry:
+  %0 = load i32* @x, align 4
+  %tobool = icmp eq i32 %0, 0
+  br i1 %tobool, label %if.end, label %foo
+
+if.end:                                           ; preds = %entry
+  %puts = tail call i32 @puts(i8* getelementptr inbounds ([4 x i8]* @str, i32 0, i32 0))
+  br label %foo
+
+foo:                                              ; preds = %entry, %if.end
+  %puts2 = tail call i32 @puts(i8* getelementptr inbounds ([4 x i8]* @str2, i32 0, i32 0))
+  ret i32 0
+}
+
+declare i32 @puts(i8* nocapture) nounwind
+