internal/load: use alias slice for determinism

Previously aliases were stored in a map which was causing
non-deterministic code generation (see recent build failures). This diff
changes to a slice to avoid this problem.

Updates #50

internal/load/annoyingaliases.sh

@@ -12,7 +12,7 @@ arch=${GOROOT}/src/cmd/asm/internal/arch/arch.go
     echo
     echo 'package load'
     echo
-    echo 'var annoyingaliases = map[string]string{'
+    echo 'var annoyingaliases = []alias{'
 
     awk '
         /archX86/ { x86=1 }
@@ -27,7 +27,7 @@ arch=${GOROOT}/src/cmd/asm/internal/arch/arch.go
             sub(/x86\.A/, "", to)
 
             if(from != to) { 
-                printf("\t\"%s\": \"%s\",\n", from, to)
+                printf("\t{\"%s\", \"%s\"},\n", from, to)
             }
         }
     ' ${arch}

internal/load/load.go

@@ -74,15 +74,19 @@ func (l *Loader) Load() ([]inst.Instruction, error) {
 		im[e.Opcode] = e
 	}
 
-	// Apply list of aliases.
-	for from, to := range aliases {
-		if existing, found := im[from]; found {
-			im[to].Forms = append(im[to].Forms, existing.Forms...)
+	// Merge aliased forms. This is primarily for MOVQ (issue #50).
+	for _, a := range aliases {
+		if existing, found := im[a.From]; found {
+			im[a.To].Forms = append(im[a.To].Forms, existing.Forms...)
 		}
-		cpy := *im[to]
-		cpy.Opcode = from
-		cpy.AliasOf = to
-		im[from] = &cpy
+	}
+
+	// Apply list of aliases.
+	for _, a := range aliases {
+		cpy := *im[a.To]
+		cpy.Opcode = a.From
+		cpy.AliasOf = a.To
+		im[a.From] = &cpy
 	}
 
 	// Dedupe forms.

internal/load/tables.go

@@ -4,9 +4,15 @@ import (
 	"github.com/mmcloughlin/avo/internal/inst"
 )
 
+// alias defines an opcode alias.
+type alias struct {
+	From string
+	To   string
+}
+
 // aliases defines a list of opcode aliases. Where possible these are extracted
 // from the code (see note below).
-var aliases = map[string]string{
+var aliases = []alias{
 	// The PSHUFD/PSHUFL alias is not recorded in the list of "Annoying aliases" below. However the instructions are identical.
 	//
 	// Reference: https://github.com/golang/go/blob/048c9164a0c5572df18325e377473e7893dbfb07/src/cmd/internal/obj/x86/asm6.go#L1365
@@ -17,7 +23,7 @@ var aliases = map[string]string{
 	//
 	//		{APSHUFD, yxshuf, Pq, opBytes{0x70, 0}},
 	//
-	"PSHUFD": "PSHUFL",
+	{"PSHUFD", "PSHUFL"},
 }
 
 // Go contains a list of self-proclaimed "Annoying aliases", as follows. We use
@@ -88,9 +94,7 @@ var aliases = map[string]string{
 //go:generate ./annoyingaliases.sh zannoyingaliases.go
 
 func init() {
-	for from, to := range annoyingaliases {
-		aliases[from] = to
-	}
+	aliases = append(aliases, annoyingaliases...)
 }
 
 // extras is simply a list of extra instructions to add to the database.

internal/load/zannoyingaliases.go

@@ -2,42 +2,42 @@
 
 package load
 
-var annoyingaliases = map[string]string{
-	"JA":         "JHI",
-	"JAE":        "JCC",
-	"JB":         "JCS",
-	"JBE":        "JLS",
-	"JC":         "JCS",
-	"JE":         "JEQ",
-	"JG":         "JGT",
-	"JHS":        "JCC",
-	"JL":         "JLT",
-	"JLO":        "JCS",
-	"JNA":        "JLS",
-	"JNAE":       "JCS",
-	"JNB":        "JCC",
-	"JNBE":       "JHI",
-	"JNC":        "JCC",
-	"JNG":        "JLE",
-	"JNGE":       "JLT",
-	"JNL":        "JGE",
-	"JNLE":       "JGT",
-	"JNO":        "JOC",
-	"JNP":        "JPC",
-	"JNS":        "JPL",
-	"JNZ":        "JNE",
-	"JO":         "JOS",
-	"JP":         "JPS",
-	"JPE":        "JPS",
-	"JPO":        "JPC",
-	"JS":         "JMI",
-	"JZ":         "JEQ",
-	"MASKMOVDQU": "MASKMOVOU",
-	"MOVD":       "MOVQ",
-	"MOVDQ2Q":    "MOVQ",
-	"MOVNTDQ":    "MOVNTO",
-	"MOVOA":      "MOVO",
-	"PSLLDQ":     "PSLLO",
-	"PSRLDQ":     "PSRLO",
-	"PADDD":      "PADDL",
+var annoyingaliases = []alias{
+	{"JA", "JHI"},
+	{"JAE", "JCC"},
+	{"JB", "JCS"},
+	{"JBE", "JLS"},
+	{"JC", "JCS"},
+	{"JE", "JEQ"},
+	{"JG", "JGT"},
+	{"JHS", "JCC"},
+	{"JL", "JLT"},
+	{"JLO", "JCS"},
+	{"JNA", "JLS"},
+	{"JNAE", "JCS"},
+	{"JNB", "JCC"},
+	{"JNBE", "JHI"},
+	{"JNC", "JCC"},
+	{"JNG", "JLE"},
+	{"JNGE", "JLT"},
+	{"JNL", "JGE"},
+	{"JNLE", "JGT"},
+	{"JNO", "JOC"},
+	{"JNP", "JPC"},
+	{"JNS", "JPL"},
+	{"JNZ", "JNE"},
+	{"JO", "JOS"},
+	{"JP", "JPS"},
+	{"JPE", "JPS"},
+	{"JPO", "JPC"},
+	{"JS", "JMI"},
+	{"JZ", "JEQ"},
+	{"MASKMOVDQU", "MASKMOVOU"},
+	{"MOVD", "MOVQ"},
+	{"MOVDQ2Q", "MOVQ"},
+	{"MOVNTDQ", "MOVNTO"},
+	{"MOVOA", "MOVO"},
+	{"PSLLDQ", "PSLLO"},
+	{"PSRLDQ", "PSRLO"},
+	{"PADDD", "PADDL"},
 }