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improve support for big endian targets, fixing PR8171, patch 

by Heikki Kultala!

llvm-svn: 125784
This commit is contained in:
Chris Lattner 2011-02-17 22:09:58 +00:00
parent 79b52bfc46
commit fb59c7c7d8
2 changed files with 16 additions and 3 deletions
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2
clang/lib/CodeGen/CGExprConstant.cpp
View File

@ -231,7 +231,7 @@ void ConstStructBuilder::AppendBitField(const FieldDecl *Field,
if (CGM.getTargetData().isBigEndian()) {
// We want the high bits.
Tmp = FieldValue.lshr(Tmp.getBitWidth() - 8).trunc(8);
Tmp = FieldValue.lshr(FieldValue.getBitWidth() - 8).trunc(8);
} else {
// We want the low bits.
Tmp = FieldValue.trunc(8);

17
clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
View File

@ -225,6 +225,12 @@ CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types,
FieldSize = TypeSizeInBits;
}
// in big-endian machines the first fields are in higher bit positions,
// so revert the offset. The byte offsets are reversed(back) later.
if (Types.getTargetData().isBigEndian()) {
FieldOffset = ((ContainingTypeSizeInBits)-FieldOffset-FieldSize);
}
// Compute the access components. The policy we use is to start by attempting
// to access using the width of the bit-field type itself and to always access
// at aligned indices of that type. If such an access would fail because it
@ -232,7 +238,6 @@ CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types,
// power of two and retry. The current algorithm assumes pow2 sized types,
// although this is easy to fix.
//
// FIXME: This algorithm is wrong on big-endian systems, I think.
assert(llvm::isPowerOf2_32(TypeSizeInBits) && "Unexpected type size!");
CGBitFieldInfo::AccessInfo Components[3];
unsigned NumComponents = 0;
@ -280,7 +285,15 @@ CGBitFieldInfo CGBitFieldInfo::MakeInfo(CodeGenTypes &Types,
// FIXME: We still follow the old access pattern of only using the field
// byte offset. We should switch this once we fix the struct layout to be
// pretty.
AI.FieldByteOffset = AccessStart / 8;
// on big-endian machines we reverted the bit offset because first fields are
// in higher bits. But this also reverts the bytes, so fix this here by reverting
// the byte offset on big-endian machines.
if (Types.getTargetData().isBigEndian()) {
AI.FieldByteOffset = (ContainingTypeSizeInBits - AccessStart - AccessWidth )/8;
} else {
AI.FieldByteOffset = AccessStart / 8;
}
AI.FieldBitStart = AccessBitsInFieldStart - AccessStart;
AI.AccessWidth = AccessWidth;
AI.AccessAlignment = llvm::MinAlign(ContainingTypeAlign, AccessStart) / 8;