all: AVX-512 (#217)

Extends avo to support most AVX-512 instruction sets.

The instruction type is extended to support suffixes. The K family of opmask
registers is added to the register package, and the operand package is updated
to support the new operand types. Move instruction deduction in `Load` and
`Store` is extended to support KMOV* and VMOV* forms.

Internal code generation packages were overhauled. Instruction database loading
required various messy changes to account for the additional complexities of the
AVX-512 instruction sets. The internal/api package was added to introduce a
separation between instruction forms in the database, and the functions avo
provides to create them. This was required since with instruction suffixes there
is no longer a one-to-one mapping between instruction constructors and opcodes.

AVX-512 bloated generated source code size substantially, initially increasing
compilation and CI test times to an unacceptable level. Two changes were made to
address this:

1.  Instruction constructors in the `x86` package moved to an optab-based
    approach. This compiles substantially faster than the verbose code
    generation we had before.

2.  The most verbose code-generated tests are moved under build tags and
    limited to a stress test mode. Stress test builds are run on
    schedule but not in regular CI.

An example of AVX-512 accelerated 16-lane MD5 is provided to demonstrate and
test the new functionality.

Updates #20 #163 #229

Co-authored-by: Vaughn Iverson <vsivsi@yahoo.com>

internal/api/function_test.go

@@ -0,0 +1,50 @@
+package api
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/mmcloughlin/avo/internal/inst"
+)
+
+func TestFunctionsDuplicateFormSignatures(t *testing.T) {
+	// Test for duplicate form signatures within a given function. This could
+	// manifest as duplicate case statements in generated code.
+	fns := InstructionsFunctions(inst.Instructions)
+	for _, fn := range fns {
+		fn := fn // scopelint
+		t.Run(fn.Name(), func(t *testing.T) {
+			seen := map[string]bool{}
+			for _, f := range fn.Forms {
+				sig := strings.Join(f.Signature(), "_")
+				t.Log(sig)
+				if seen[sig] {
+					t.Fatalf("duplicate: %s", sig)
+				}
+				seen[sig] = true
+			}
+		})
+	}
+}
+
+func TestFunctionsUniqueArgNames(t *testing.T) {
+	fns := InstructionsFunctions(inst.Instructions)
+	for _, fn := range fns {
+		s := fn.Signature()
+		for _, n := range fn.Arities() {
+			if n == 0 {
+				continue
+			}
+			names := map[string]bool{}
+			for j := 0; j < n; j++ {
+				names[s.ParameterName(j)] = true
+			}
+			if len(names) != n {
+				t.Errorf("repeated argument for instruction %s", fn.Name())
+			}
+			if _, found := names[""]; found {
+				t.Errorf("empty argument name for instruction %s", fn.Name())
+			}
+		}
+	}
+}