[PATCH] Disable DAGCombine for -O0 and optnone

[Elena Demikhovsky]

All lit tests should pass in the -O0 mode. The code may be not optimal, but the compilation should not fail and the generated code should correct.


REPOSITORY
  rL LLVM

================
Comment at: lib/Target/X86/X86ISelLowering.cpp:17616
@@ -17608,1 +17615,3 @@
 
+SDValue X86TargetLowering::LowerFMA(SDValue Op, SelectionDAG &DAG) const {
+  SDLoc dl(Op);
----------------
You should not do the work of DAG-combiner in lowering. Lowering should deal with one SDNode.
Please put the FMA-combine back and just translate ISD::FMA to X86ISD::FMADD here.

http://reviews.llvm.org/D9992

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