core/vm, crypto/bn256: switch over to cloudflare library (#16203)

* core/vm, crypto/bn256: switch over to cloudflare library

* crypto/bn256: unmarshal constraint + start pure go impl

* crypto/bn256: combo cloudflare and google lib

* travis: drop 386 test job

crypto/bn256/cloudflare/gfp_test.go

@@ -0,0 +1,62 @@
+// +build amd64,!appengine,!gccgo
+
+package bn256
+
+import (
+	"testing"
+)
+
+// Tests that negation works the same way on both assembly-optimized and pure Go
+// implementation.
+func TestGFpNeg(t *testing.T) {
+	n := &gfP{0x0123456789abcdef, 0xfedcba9876543210, 0xdeadbeefdeadbeef, 0xfeebdaedfeebdaed}
+	w := &gfP{0xfedcba9876543211, 0x0123456789abcdef, 0x2152411021524110, 0x0114251201142512}
+	h := &gfP{}
+
+	gfpNeg(h, n)
+	if *h != *w {
+		t.Errorf("negation mismatch: have %#x, want %#x", *h, *w)
+	}
+}
+
+// Tests that addition works the same way on both assembly-optimized and pure Go
+// implementation.
+func TestGFpAdd(t *testing.T) {
+	a := &gfP{0x0123456789abcdef, 0xfedcba9876543210, 0xdeadbeefdeadbeef, 0xfeebdaedfeebdaed}
+	b := &gfP{0xfedcba9876543210, 0x0123456789abcdef, 0xfeebdaedfeebdaed, 0xdeadbeefdeadbeef}
+	w := &gfP{0xc3df73e9278302b8, 0x687e956e978e3572, 0x254954275c18417f, 0xad354b6afc67f9b4}
+	h := &gfP{}
+
+	gfpAdd(h, a, b)
+	if *h != *w {
+		t.Errorf("addition mismatch: have %#x, want %#x", *h, *w)
+	}
+}
+
+// Tests that subtraction works the same way on both assembly-optimized and pure Go
+// implementation.
+func TestGFpSub(t *testing.T) {
+	a := &gfP{0x0123456789abcdef, 0xfedcba9876543210, 0xdeadbeefdeadbeef, 0xfeebdaedfeebdaed}
+	b := &gfP{0xfedcba9876543210, 0x0123456789abcdef, 0xfeebdaedfeebdaed, 0xdeadbeefdeadbeef}
+	w := &gfP{0x02468acf13579bdf, 0xfdb97530eca86420, 0xdfc1e401dfc1e402, 0x203e1bfe203e1bfd}
+	h := &gfP{}
+
+	gfpSub(h, a, b)
+	if *h != *w {
+		t.Errorf("subtraction mismatch: have %#x, want %#x", *h, *w)
+	}
+}
+
+// Tests that multiplication works the same way on both assembly-optimized and pure Go
+// implementation.
+func TestGFpMul(t *testing.T) {
+	a := &gfP{0x0123456789abcdef, 0xfedcba9876543210, 0xdeadbeefdeadbeef, 0xfeebdaedfeebdaed}
+	b := &gfP{0xfedcba9876543210, 0x0123456789abcdef, 0xfeebdaedfeebdaed, 0xdeadbeefdeadbeef}
+	w := &gfP{0xcbcbd377f7ad22d3, 0x3b89ba5d849379bf, 0x87b61627bd38b6d2, 0xc44052a2a0e654b2}
+	h := &gfP{}
+
+	gfpMul(h, a, b)
+	if *h != *w {
+		t.Errorf("multiplication mismatch: have %#x, want %#x", *h, *w)
+	}
+}