[llvm] r181891 - [PowerPC] Correctly handle fixups of other than 4 byte size

[Ulrich Weigand]

Author: uweigand
Date: Wed May 15 10:01:46 2013
New Revision: 181891

URL: http://llvm.org/viewvc/llvm-project?rev=181891&view=rev
Log:

[PowerPC] Correctly handle fixups of other than 4 byte size

The PPCAsmBackend::applyFixup routine handles the case where a
fixup can be resolved within the same object file.  However,
this routine is currently hard-coded to assume the size of
any fixup is always exactly 4 bytes.

This is sort-of correct for fixups on instruction text; even
though it only works because several of what really would be
2-byte fixups are presented as 4-byte fixups instead (requiring
another hack in PPCELFObjectWriter::adjustFixupOffset to clean
it up).

However, this assumption breaks down completely for fixups
on data, which legitimately can be of any size (1, 2, 4, or 8).

This patch makes applyFixup aware of fixups of varying sizes,
introducing a new helper routine getFixupKindNumBytes (along
the lines of what the ARM back end does).  Note that in order
to handle fixups of size 8, we also need to fix the return type
of adjustFixupValue to uint64_t to avoid truncation.

Tested on both 64-bit and 32-bit PowerPC, using external and
integrated assembler.


Modified:
    llvm/trunk/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp

Modified: llvm/trunk/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp?rev=181891&r1=181890&r2=181891&view=diff
==============================================================================
--- llvm/trunk/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp (original)
+++ llvm/trunk/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp Wed May 15 10:01:46 2013
@@ -22,7 +22,7 @@
 #include "llvm/Support/TargetRegistry.h"
 using namespace llvm;
 
-static unsigned adjustFixupValue(unsigned Kind, uint64_t Value) {
+static uint64_t adjustFixupValue(unsigned Kind, uint64_t Value) {
   switch (Kind) {
   default:
     llvm_unreachable("Unknown fixup kind!");
@@ -50,6 +50,29 @@ static unsigned adjustFixupValue(unsigne
   }
 }
 
+static unsigned getFixupKindNumBytes(unsigned Kind) {
+  switch (Kind) {
+  default:
+    llvm_unreachable("Unknown fixup kind!");
+  case FK_Data_1:
+    return 1;
+  case FK_Data_2:
+    return 2;
+  case FK_Data_4:
+  case PPC::fixup_ppc_brcond14:
+  case PPC::fixup_ppc_br24:
+  case PPC::fixup_ppc_ha16:
+  case PPC::fixup_ppc_lo16:
+  case PPC::fixup_ppc_lo16_ds:
+    return 4;
+  case FK_Data_8:
+    return 8;
+  case PPC::fixup_ppc_tlsreg:
+  case PPC::fixup_ppc_nofixup:
+    return 0;
+  }
+}
+
 namespace {
 class PPCMachObjectWriter : public MCMachObjectTargetWriter {
 public:
@@ -98,12 +121,13 @@ public:
     if (!Value) return;           // Doesn't change encoding.
 
     unsigned Offset = Fixup.getOffset();
+    unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind());
 
     // For each byte of the fragment that the fixup touches, mask in the bits
     // from the fixup value. The Value has been "split up" into the appropriate
     // bitfields above.
-    for (unsigned i = 0; i != 4; ++i)
-      Data[Offset + i] |= uint8_t((Value >> ((4 - i - 1)*8)) & 0xff);
+    for (unsigned i = 0; i != NumBytes; ++i)
+      Data[Offset + i] |= uint8_t((Value >> ((NumBytes - i - 1)*8)) & 0xff);
   }
 
   bool mayNeedRelaxation(const MCInst &Inst) const {