removes fp751ConditionalAssign

p751toolbox/field.go

@@ -210,18 +210,6 @@ func ExtensionFieldConditionalSwap(x, y *ExtensionFieldElement, choice uint8) {
 	fp751ConditionalSwap(&x.B, &y.B, choice)
 }
 
-// Set dest = if choice == 0 { x } else { y }, in constant time.
-//
-// Can overlap z with x or y or both.
-//
-// Returns dest to allow chaining operations.
-func (dest *ExtensionFieldElement) ConditionalAssign(x, y *ExtensionFieldElement, choice uint8) *ExtensionFieldElement {
-	fp751ConditionalAssign(&dest.A, &x.A, &y.A, choice)
-	fp751ConditionalAssign(&dest.B, &x.B, &y.B, choice)
-
-	return dest
-}
-
 // Returns true if lhs = rhs.  Takes variable time.
 func (lhs *ExtensionFieldElement) VartimeEq(rhs *ExtensionFieldElement) bool {
 	return lhs.A.vartimeEq(rhs.A) && lhs.B.vartimeEq(rhs.B)
@@ -387,17 +375,6 @@ func PrimeFieldConditionalSwap(x, y *PrimeFieldElement, choice uint8) {
 	fp751ConditionalSwap(&x.A, &y.A, choice)
 }
 
-// Set dest = if choice == 0 { x } else { y }, in constant time.
-//
-// Can overlap z with x or y or both.
-//
-// Returns dest to allow chaining operations.
-func (dest *PrimeFieldElement) ConditionalAssign(x, y *PrimeFieldElement, choice uint8) *PrimeFieldElement {
-	fp751ConditionalAssign(&dest.A, &x.A, &y.A, choice)
-
-	return dest
-}
-
 // Set dest = sqrt(x), if x is a square.  If x is nonsquare dest is undefined.
 //
 // Allowed to overlap x with dest.
@@ -500,13 +477,6 @@ type fp751X2 [2 * fp751NumWords]uint64
 //go:noescape
 func fp751ConditionalSwap(x, y *Fp751Element, choice uint8)
 
-// If choice = 0, set z = x. If choice = 1, set z = y.
-// This function executes in constant time.
-//
-// Can overlap z with x or y or both.
-//go:noescape
-func fp751ConditionalAssign(z, x, y *Fp751Element, choice uint8)
-
 // Compute z = x + y (mod p).
 //go:noescape
 func fp751AddReduced(z, x, y *Fp751Element)

p751toolbox/field_amd64.s

@@ -250,101 +250,6 @@ TEXT ·fp751ConditionalSwap(SB), NOSPLIT, $0-17
 
 	RET
 
-TEXT ·fp751ConditionalAssign(SB), NOSPLIT, $0-25
-
-	MOVQ	z+0(FP), REG_P3
-	MOVQ	x+8(FP), REG_P1
-	MOVQ	y+16(FP), REG_P2
-	MOVB	choice+24(FP), AL	// AL = 0 or 1
-	MOVBLZX	AL, AX			// AX = 0 or 1
-	NEGQ	AX			// RAX = 0x00..00 or 0xff..ff
-
-	MOVQ	(0*8)(REG_P1), BX	// BX = x[0]
-	MOVQ 	(0*8)(REG_P2), CX	// CX = y[0]
-	XORQ	BX, CX			// CX = y[0] ^ x[0]
-	ANDQ	AX, CX			// CX = (y[0] ^ x[0]) & mask
-	XORQ	BX, CX			// CX = (y[0] ^ x[0]) & mask) ^ x[0]
-	MOVQ	CX, (0*8)(REG_P3)	//    = x[0] or y[0]
-
-	MOVQ	(1*8)(REG_P1), BX
-	MOVQ 	(1*8)(REG_P2), CX
-	XORQ	BX, CX
-	ANDQ	AX, CX
-	XORQ	BX, CX
-	MOVQ	CX, (1*8)(REG_P3)
-
-	MOVQ	(2*8)(REG_P1), BX
-	MOVQ 	(2*8)(REG_P2), CX
-	XORQ	BX, CX
-	ANDQ	AX, CX
-	XORQ	BX, CX
-	MOVQ	CX, (2*8)(REG_P3)
-
-	MOVQ	(3*8)(REG_P1), BX
-	MOVQ 	(3*8)(REG_P2), CX
-	XORQ	BX, CX
-	ANDQ	AX, CX
-	XORQ	BX, CX
-	MOVQ	CX, (3*8)(REG_P3)
-
-	MOVQ	(4*8)(REG_P1), BX
-	MOVQ 	(4*8)(REG_P2), CX
-	XORQ	BX, CX
-	ANDQ	AX, CX
-	XORQ	BX, CX
-	MOVQ	CX, (4*8)(REG_P3)
-
-	MOVQ	(5*8)(REG_P1), BX
-	MOVQ 	(5*8)(REG_P2), CX
-	XORQ	BX, CX
-	ANDQ	AX, CX
-	XORQ	BX, CX
-	MOVQ	CX, (5*8)(REG_P3)
-
-	MOVQ	(6*8)(REG_P1), BX
-	MOVQ 	(6*8)(REG_P2), CX
-	XORQ	BX, CX
-	ANDQ	AX, CX
-	XORQ	BX, CX
-	MOVQ	CX, (6*8)(REG_P3)
-
-	MOVQ	(7*8)(REG_P1), BX
-	MOVQ 	(7*8)(REG_P2), CX
-	XORQ	BX, CX
-	ANDQ	AX, CX
-	XORQ	BX, CX
-	MOVQ	CX, (7*8)(REG_P3)
-
-	MOVQ	(8*8)(REG_P1), BX
-	MOVQ 	(8*8)(REG_P2), CX
-	XORQ	BX, CX
-	ANDQ	AX, CX
-	XORQ	BX, CX
-	MOVQ	CX, (8*8)(REG_P3)
-
-	MOVQ	(9*8)(REG_P1), BX
-	MOVQ 	(9*8)(REG_P2), CX
-	XORQ	BX, CX
-	ANDQ	AX, CX
-	XORQ	BX, CX
-	MOVQ	CX, (9*8)(REG_P3)
-
-	MOVQ	(10*8)(REG_P1), BX
-	MOVQ 	(10*8)(REG_P2), CX
-	XORQ	BX, CX
-	ANDQ	AX, CX
-	XORQ	BX, CX
-	MOVQ	CX, (10*8)(REG_P3)
-
-	MOVQ	(11*8)(REG_P1), BX
-	MOVQ 	(11*8)(REG_P2), CX
-	XORQ	BX, CX
-	ANDQ	AX, CX
-	XORQ	BX, CX
-	MOVQ	CX, (11*8)(REG_P3)
-
-	RET
-
 TEXT ·fp751AddReduced(SB), NOSPLIT, $0-24
 
 	MOVQ	z+0(FP), REG_P3

p751toolbox/field_test.go

@@ -390,24 +390,6 @@ func TestFp751ElementConditionalSwap(t *testing.T) {
 	}
 }
 
-func TestFp751ElementConditionalAssign(t *testing.T) {
-	var one = Fp751Element{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
-	var two = Fp751Element{2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2}
-	var three = Fp751Element{3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3}
-
-	fp751ConditionalAssign(&one, &two, &three, 0)
-
-	if one != two {
-		t.Error("Found", one, "expected", two)
-	}
-
-	fp751ConditionalAssign(&one, &two, &three, 1)
-
-	if one != three {
-		t.Error("Found", one, "expected", three)
-	}
-}
-
 // Package-level storage for this field element is intended to deter
 // compiler optimizations.
 var benchmarkFp751Element Fp751Element