Fix ppcf128 component access on little-endian systems

The PowerPC 128-bit long double data type (ppcf128 in LLVM) is in fact a
pair of two doubles, where one is considered the "high" or
more-significant part, and the other is considered the "low" or
less-significant part.  When a ppcf128 value is stored in memory or a
register pair, the high part always comes first, i.e. at the lower
memory address or in the lower-numbered register, and the low part
always comes second.  This is true both on big-endian and little-endian
PowerPC systems.  (Similar to how with a complex number, the real part
always comes first and the imaginary part second, no matter the byte
order of the system.)

This was implemented incorrectly for little-endian systems in LLVM.
This commit fixes three related issues:

- When printing an immediate ppcf128 constant to assembler output
  in emitGlobalConstantFP, emit the high part first on both big-
  and little-endian systems.

- When lowering a ppcf128 type to a pair of f64 types in SelectionDAG
  (which is used e.g. when generating code to load an argument into a
  register pair), use correct low/high part ordering on little-endian
  systems.

- In a related issue, because lowering ppcf128 into a pair of f64 must
  operate differently from lowering an int128 into a pair of i64,
  bitcasts between ppcf128 and int128 must not be optimized away by the
  DAG combiner on little-endian systems, but must effect a word-swap.

Reviewed by Hal Finkel.

llvm-svn: 212274

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 249683f0201..28d8e984349 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -169,7 +169,7 @@ static SDValue getCopyFromParts(SelectionDAG &DAG, SDLoc DL,
       SDValue Lo, Hi;
       Lo = DAG.getNode(ISD::BITCAST, DL, EVT(MVT::f64), Parts[0]);
       Hi = DAG.getNode(ISD::BITCAST, DL, EVT(MVT::f64), Parts[1]);
-      if (TLI.isBigEndian())
+      if (TLI.hasBigEndianPartOrdering(ValueVT))
         std::swap(Lo, Hi);
       Val = DAG.getNode(ISD::BUILD_PAIR, DL, ValueVT, Lo, Hi);
     } else {