MIPS: Add float instructions and test coverage, part one

src/mips/constants-mips.h

Index: src/mips/constants-mips.h
diff --git a/src/mips/constants-mips.h b/src/mips/constants-mips.h
index 81f755b32006f47324513bbbfcd782e1b5dfe962..98279cbf06cc04f395ea43e978bab8d361bb985c 100644
--- a/src/mips/constants-mips.h
+++ b/src/mips/constants-mips.h
@@ -486,6 +486,8 @@ enum SecondaryField {
   TRUNC_W_D = ((1 << 3) + 5),
   CEIL_W_D = ((1 << 3) + 6),
   FLOOR_W_D = ((1 << 3) + 7),
+  RECIP = ((2 << 3) + 5),
+  RSQRT_D = ((2 << 3) + 6),

[paul.l..., 2015/05/09 01:07:47]

These two should be named consistently. Since they are both *.fmt, you should
remove the _D from RSQRT.

Should we even implement instructions for these? The manual says both are
approximations: "The numeric accuracy of this operation is implementation
dependent; it does not meet the accuracy specified by the IEEE 754 Floating
Point standard. The computed result differs from both the exact result and the
IEEE-mandated representation of the exact result by no more than two units in
the least-significant place (ULP)."

If we have a need now, put them in. If we do not have a need that can tolerate
the inaccuracy, we might want to skip these. If we do not skip, we should add
comments to the assembler files where they are defined, so someone does not use
them in a way that requires accuracy.

[dusmil.imgtec, 2015/05/11 13:13:24]

For the sake of simulator completeness, let's leave them in code.
Their names already mean approximation, so if programmers used them they used to
know their behavior.

[Djordje.Pesic, 2015/05/14 13:22:30]

Done.

[Djordje.Pesic, 2015/05/14 13:22:30]

Done.

   MIN = ((3 << 3) + 4),
   MINA = ((3 << 3) + 5),
   MAX = ((3 << 3) + 6),
@@ -544,7 +546,10 @@ enum SecondaryField {
   CMP_SOGT = ((3 << 3) + 7),  // Reserved, not implemented.
 
   SEL = ((2 << 3) + 0),
+  MOVZ_C = ((2 << 3) + 2),
+  MOVN_C = ((2 << 3) + 3),

[paul.l..., 2015/05/09 01:07:47]

Other FP instructions that have _C suffix (to differentiate from integer
version), have an explicit comment:
 // COP1 on FPR registers. 
Please add that here.

[Djordje.Pesic, 2015/05/14 13:22:30]

Done.

   SELEQZ_C = ((2 << 3) + 4),  // COP1 on FPR registers.
+  MOVF = ((2 << 3) + 1),      // Function field for MOVT.fmt and MOVF.fmt
   SELNEZ_C = ((2 << 3) + 7),  // COP1 on FPR registers.
   // COP1 Encoding of Function Field When rs=PS.
   // COP1X Encoding of Function Field.