Cleanup PPC(64) i32 -> float/double conversion

The existing SINT_TO_FP code for i32 -> float/double conversion was disabled
because it relied on broken EXTSW_32/STD_32 instruction definitions. The
original intent had been to enable these 64-bit instructions to be used on CPUs
that support them even in 32-bit mode.  Unfortunately, this form of lying to
the infrastructure was buggy (as explained in the FIXME comment) and had
therefore been disabled.

This re-enables this functionality, using regular DAG nodes, but only when
compiling in 64-bit mode. The old STD_32/EXTSW_32 definitions (which were dead)
are removed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178438 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PowerPC/PPCISelLowering.h b/lib/Target/PowerPC/PPCISelLowering.h
index 6296400..bce05a1 100644
--- a/lib/Target/PowerPC/PPCISelLowering.h
+++ b/lib/Target/PowerPC/PPCISelLowering.h
@@ -91,10 +91,6 @@
       /// code.
       SRL, SRA, SHL,
 
-      /// EXTSW_32 - This is the EXTSW instruction for use with "32-bit"
-      /// registers.
-      EXTSW_32,
-
       /// CALL - A direct function call.
       /// CALL_NOP is a call with the special NOP which follows 64-bit
       /// SVR4 calls.
@@ -234,14 +230,11 @@
       /// optimizations due to constant folding.
       VADD_SPLAT,
 
-      /// STD_32 - This is the STD instruction for use with "32-bit" registers.
-      STD_32 = ISD::FIRST_TARGET_MEMORY_OPCODE,
-
       /// CHAIN = STBRX CHAIN, GPRC, Ptr, Type - This is a
       /// byte-swapping store instruction.  It byte-swaps the low "Type" bits of
       /// the GPRC input, then stores it through Ptr.  Type can be either i16 or
       /// i32.
-      STBRX,
+      STBRX = ISD::FIRST_TARGET_MEMORY_OPCODE,
 
       /// GPRC, CHAIN = LBRX CHAIN, Ptr, Type - This is a
       /// byte-swapping load instruction.  It loads "Type" bits, byte swaps it,