PowerPC: Simplify FADD in round-to-zero mode.

As part of the the sequence generated to implement long double -> int
conversions, we need to perform an FADD in round-to-zero mode.  This is
problematical since the FPSCR is not at all modeled at the SelectionDAG
level, and thus there is a risk of getting floating point instructions
generated out of sequence with the instructions to modify FPSCR.

The current code handles this by somewhat "special" patterns that in part
have dummy operands, and/or duplicate existing instructions, making them
awkward to handle in the asm parser.

This commit changes this by leaving the "FADD in round-to-zero mode"
as an atomic operation on the SelectionDAG level, and only split it up into
real instructions at the MI level (via custom inserter).  Since at *this*
level the FPSCR *is* modeled (via the "RM" hard register), much of the
"special" stuff can just go away, and the resulting patterns can be used by
the asm parser.

No significant change in generated code expected.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178006 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 2 deletions

diff --git a/lib/Target/PowerPC/PPCInstrFormats.td b/lib/Target/PowerPC/PPCInstrFormats.td
index c4fd192950..129c5855aa 100644
--- a/lib/Target/PowerPC/PPCInstrFormats.td
+++ b/lib/Target/PowerPC/PPCInstrFormats.td
@@ -676,14 +676,13 @@ class XFXForm_7_ext<bits<6> opcode, bits<10> xo, bits<10> spr,
 // This is probably 1.7.9, but I don't have the reference that uses this
 // numbering scheme...
 class XFLForm<bits<6> opcode, bits<10> xo, dag OOL, dag IOL, string asmstr, 
-                      string cstr, InstrItinClass itin, list<dag>pattern>
+              InstrItinClass itin, list<dag>pattern>
   : I<opcode, OOL, IOL, asmstr, itin> {
   bits<8> FM;
   bits<5> rT;
 
   bit RC = 0;    // set by isDOT
   let Pattern = pattern;
-  let Constraints = cstr;
 
   let Inst{6} = 0;
   let Inst{7-14}  = FM;