[mips] Fix c.<cc>.<fmt> instruction definition.

As part of this effort, remove MipsFCmp nodes and use tablegen
patterns rather than custom lowering through C++.

Unexpectedly, this improves codesize for microMIPS as previous floating
point setcc expansions would materialize 0 and 1 into GPRs before using
the relevant mov[tf].[sd] instruction. Now $zero is used directly.

Reviewers: dsanders, vkalintiris, zoran.jovanovic

Differential Review: https://reviews.llvm.org/D23118

llvm-svn: 281022
diff --git a/llvm/lib/Target/Mips/MipsFastISel.cpp b/llvm/lib/Target/Mips/MipsFastISel.cpp
index 9453164..58a53a0 100644
--- a/llvm/lib/Target/Mips/MipsFastISel.cpp
+++ b/llvm/lib/Target/Mips/MipsFastISel.cpp
@@ -709,8 +709,10 @@
     unsigned RegWithOne = createResultReg(&Mips::GPR32RegClass);
     emitInst(Mips::ADDiu, RegWithZero).addReg(Mips::ZERO).addImm(0);
     emitInst(Mips::ADDiu, RegWithOne).addReg(Mips::ZERO).addImm(1);
-    emitInst(Opc).addReg(LeftReg).addReg(RightReg).addReg(
-        Mips::FCC0, RegState::ImplicitDefine);
+    emitInst(Opc)
+        .addReg(Mips::FCC0, RegState::Define)
+        .addReg(LeftReg)
+        .addReg(RightReg);
     emitInst(CondMovOpc, ResultReg)
         .addReg(RegWithOne)
         .addReg(Mips::FCC0)