[MIPS] Fix the func opcode for mina.fmt and max.fmt

- The opcode of the mina.fmt and max.fmt is documented wrong, the
  object code compiled from the same assembly with LLVM behaves
  differently than one compiled with GCC and Binutils.
- Modify the opcodes to match Binutils. The actual opcodes are as follows:

  {5,3}| bits {2,0} of func
       | ... | 100 | 101 | 110 | 111
  -----+-----+-----+-----+-----+-----
   010 | ... | min | mina| max | maxa

Author: Cyanoxygen

llvm/lib/Target/Mips/Mips32r6InstrInfo.td

@@ -153,15 +153,15 @@ class SELNEZ_ENC : SPECIAL_3R_FM<0b00000, 0b110111>;
 
 class LWPC_ENC   : PCREL19_FM<OPCODE2_LWPC>;
 
-class MAX_S_ENC : COP1_3R_FM<0b011101, FIELD_FMT_S>;
-class MAX_D_ENC : COP1_3R_FM<0b011101, FIELD_FMT_D>;
+class MAX_S_ENC : COP1_3R_FM<0b011110, FIELD_FMT_S>;
+class MAX_D_ENC : COP1_3R_FM<0b011110, FIELD_FMT_D>;
 class MIN_S_ENC : COP1_3R_FM<0b011100, FIELD_FMT_S>;
 class MIN_D_ENC : COP1_3R_FM<0b011100, FIELD_FMT_D>;
 
 class MAXA_S_ENC : COP1_3R_FM<0b011111, FIELD_FMT_S>;
 class MAXA_D_ENC : COP1_3R_FM<0b011111, FIELD_FMT_D>;
-class MINA_S_ENC : COP1_3R_FM<0b011110, FIELD_FMT_S>;
-class MINA_D_ENC : COP1_3R_FM<0b011110, FIELD_FMT_D>;
+class MINA_S_ENC : COP1_3R_FM<0b011101, FIELD_FMT_S>;
+class MINA_D_ENC : COP1_3R_FM<0b011101, FIELD_FMT_D>;
 
 class SELEQZ_S_ENC : COP1_3R_FM<0b010100, FIELD_FMT_S>;
 class SELEQZ_D_ENC : COP1_3R_FM<0b010100, FIELD_FMT_D>;
@@ -1117,6 +1117,22 @@ def : MipsPat<(select i32:$cond, immz, i32:$f),
               ISA_MIPS32R6;
 }
 
+// llvm.fmin/fmax operations.
+let AdditionalPredicates = [NotInMicroMips] in {
+  def : MipsPat<(fmaxnum f32:$lhs, f32:$rhs),
+                (MAX_S   f32:$lhs, f32:$rhs)>,
+                ISA_MIPS32R6;
+  def : MipsPat<(fmaxnum f64:$lhs, f64:$rhs),
+                (MAX_D   f64:$lhs, f64:$rhs)>,
+                ISA_MIPS32R6;
+  def : MipsPat<(fminnum f32:$lhs, f32:$rhs),
+                (MIN_S   f32:$lhs, f32:$rhs)>,
+                ISA_MIPS32R6;
+  def : MipsPat<(fminnum f64:$lhs, f64:$rhs),
+                (MIN_D   f64:$lhs, f64:$rhs)>,
+                ISA_MIPS32R6;
+}
+
 // Pseudo instructions
 let isCall = 1, isTerminator = 1, isReturn = 1, isBarrier = 1, hasDelaySlot = 1,
     hasExtraSrcRegAllocReq = 1, isCTI = 1, Defs = [AT], hasPostISelHook = 1 in {