cmd/internal/obj/arm64: fix encoding of AND MBCON

When a constant is both MOVCON (can fit into a MOV instruction)
and BITCON (can fit into a logical instruction), the assembler
chooses to use the MOVCON encoding, which is actually longer for
logical instructions. We add MBCON rules explicitly to make sure
it uses the BITCON encoding.

Updates #19857.

Change-Id: Ib9881be363cbc491ac2a0792b36b87e74eff34a8
Reviewed-on: https://go-review.googlesource.com/39652
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/asm/internal/asm/testdata/arm64.s

@@ -45,6 +45,15 @@ TEXT	foo(SB), 7, $-8
 	ADD	R1->33, R2
 	AND	R1@>33, R2
 
+// logical ops
+// make sure constants get encoded into an instruction when it could
+	AND	$(1<<63), R1   // AND	$-9223372036854775808, R1 // 21004192
+	AND	$(1<<63-1), R1 // AND	$9223372036854775807, R1  // 21f84092
+	ORR	$(1<<63), R1   // ORR	$-9223372036854775808, R1 // 210041b2
+	ORR	$(1<<63-1), R1 // ORR	$9223372036854775807, R1  // 21f840b2
+	EOR	$(1<<63), R1   // EOR	$-9223372036854775808, R1 // 210041d2
+	EOR	$(1<<63-1), R1 // EOR	$9223372036854775807, R1  // 21f840d2
+
 //
 // CLS
 //

src/cmd/internal/obj/arm64/a.out.go

@@ -254,6 +254,9 @@ const (
 )
 
 const (
+	// optab is sorted based on the order of these constants
+	// and the first match is chosen.
+	// The more specific class needs to come earlier.
 	C_NONE   = iota
 	C_REG    // R0..R30
 	C_RSP    // R0..R30, RSP
@@ -266,13 +269,13 @@ const (
 	C_COND   // EQ, NE, etc
 
 	C_ZCON     // $0 or ZR
+	C_ABCON0   // could be C_ADDCON0 or C_BITCON
 	C_ADDCON0  // 12-bit unsigned, unshifted
+	C_ABCON    // could be C_ADDCON or C_BITCON
 	C_ADDCON   // 12-bit unsigned, shifted left by 0 or 12
+	C_MBCON    // could be C_MOVCON or C_BITCON
 	C_MOVCON   // generated by a 16-bit constant, optionally inverted and/or shifted by multiple of 16
 	C_BITCON   // bitfield and logical immediate masks
-	C_ABCON0   // could be C_ADDCON0 or C_BITCON
-	C_ABCON    // could be C_ADDCON or C_BITCON
-	C_MBCON    // could be C_MOVCON or C_BITCON
 	C_LCON     // 32-bit constant
 	C_VCON     // 64-bit constant
 	C_FCON     // floating-point constant

src/cmd/internal/obj/arm64/asm7.go

@@ -190,6 +190,10 @@ var optab = []Optab{
 	{AAND, C_REG, C_NONE, C_REG, 1, 4, 0, 0, 0},
 	{ABIC, C_REG, C_REG, C_REG, 1, 4, 0, 0, 0},
 	{ABIC, C_REG, C_NONE, C_REG, 1, 4, 0, 0, 0},
+	{AAND, C_MBCON, C_REG, C_REG, 53, 4, 0, 0, 0},
+	{AAND, C_MBCON, C_NONE, C_REG, 53, 4, 0, 0, 0},
+	{ABIC, C_MBCON, C_REG, C_REG, 53, 4, 0, 0, 0},
+	{ABIC, C_MBCON, C_NONE, C_REG, 53, 4, 0, 0, 0},
 	{AAND, C_BITCON, C_REG, C_REG, 53, 4, 0, 0, 0},
 	{AAND, C_BITCON, C_NONE, C_REG, 53, 4, 0, 0, 0},
 	{ABIC, C_BITCON, C_REG, C_REG, 53, 4, 0, 0, 0},