runtime: restore arm assembly stubs for div/mod

These are used by DIV[U] and MOD[U] assembly instructions.
Add a test in the stdlib so we actually exercise linking
to these routines.

Update #19507

Change-Id: I0d8e19a53e3744abc0c661ea95486f94ec67585e
Reviewed-on: https://go-review.googlesource.com/45703Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/internal/obj/arm/asm5.go

@@ -1480,10 +1480,10 @@ func buildop(ctxt *obj.Link) {
 
 	deferreturn = ctxt.Lookup("runtime.deferreturn")
 
-	symdiv = ctxt.Lookup("_div")
-	symdivu = ctxt.Lookup("_divu")
-	symmod = ctxt.Lookup("_mod")
-	symmodu = ctxt.Lookup("_modu")
+	symdiv = ctxt.Lookup("runtime._div")
+	symdivu = ctxt.Lookup("runtime._divu")
+	symmod = ctxt.Lookup("runtime._mod")
+	symmodu = ctxt.Lookup("runtime._modu")
 
 	var n int
 

src/runtime/softfloat_arm.go

@@ -655,6 +655,10 @@ func sfloat2(pc uint32, regs *[15]uint32) uint32 {
 }
 
 // Stubs to pacify vet. Not safe to call from Go.
-// Calls to these functions are inserted by the compiler.
+// Calls to these functions are inserted by the compiler or assembler.
 func _sfloat()
 func udiv()
+func _div()
+func _divu()
+func _mod()
+func _modu()

src/runtime/vlop_arm.s

@@ -199,6 +199,118 @@ DATA fast_udiv_tab<>+0x38(SB)/4, $0x85868788
 DATA fast_udiv_tab<>+0x3c(SB)/4, $0x81828384
 GLOBL fast_udiv_tab<>(SB), RODATA, $64
 
+// The linker will pass numerator in R8
+#define Rn R8
+// The linker expects the result in RTMP
+#define RTMP R11
+
+TEXT runtime·_divu(SB), NOSPLIT, $16-0
+	// It's not strictly true that there are no local pointers.
+	// It could be that the saved registers Rq, Rr, Rs, and Rm
+	// contain pointers. However, the only way this can matter
+	// is if the stack grows (which it can't, udiv is nosplit)
+	// or if a fault happens and more frames are added to
+	// the stack due to deferred functions.
+	// In the latter case, the stack can grow arbitrarily,
+	// and garbage collection can happen, and those
+	// operations care about pointers, but in that case
+	// the calling frame is dead, and so are the saved
+	// registers. So we can claim there are no pointers here.
+	NO_LOCAL_POINTERS
+	MOVW	Rq, 4(R13)
+	MOVW	Rr, 8(R13)
+	MOVW	Rs, 12(R13)
+	MOVW	RM, 16(R13)
+
+	MOVW	Rn, Rr			/* numerator */
+	MOVW	g_m(g), Rq
+	MOVW	m_divmod(Rq), Rq	/* denominator */
+	BL  	runtime·udiv(SB)
+	MOVW	Rq, RTMP
+	MOVW	4(R13), Rq
+	MOVW	8(R13), Rr
+	MOVW	12(R13), Rs
+	MOVW	16(R13), RM
+	RET
+
+TEXT runtime·_modu(SB), NOSPLIT, $16-0
+	NO_LOCAL_POINTERS
+	MOVW	Rq, 4(R13)
+	MOVW	Rr, 8(R13)
+	MOVW	Rs, 12(R13)
+	MOVW	RM, 16(R13)
+
+	MOVW	Rn, Rr			/* numerator */
+	MOVW	g_m(g), Rq
+	MOVW	m_divmod(Rq), Rq	/* denominator */
+	BL  	runtime·udiv(SB)
+	MOVW	Rr, RTMP
+	MOVW	4(R13), Rq
+	MOVW	8(R13), Rr
+	MOVW	12(R13), Rs
+	MOVW	16(R13), RM
+	RET
+
+TEXT runtime·_div(SB),NOSPLIT,$16-0
+	NO_LOCAL_POINTERS
+	MOVW	Rq, 4(R13)
+	MOVW	Rr, 8(R13)
+	MOVW	Rs, 12(R13)
+	MOVW	RM, 16(R13)
+	MOVW	Rn, Rr			/* numerator */
+	MOVW	g_m(g), Rq
+	MOVW	m_divmod(Rq), Rq	/* denominator */
+	CMP 	$0, Rr
+	BGE 	d1
+	RSB 	$0, Rr, Rr
+	CMP 	$0, Rq
+	BGE 	d2
+	RSB 	$0, Rq, Rq
+d0:
+	BL  	runtime·udiv(SB)  	/* none/both neg */
+	MOVW	Rq, RTMP
+	B	out1
+d1:
+	CMP 	$0, Rq
+	BGE 	d0
+	RSB 	$0, Rq, Rq
+d2:
+	BL  	runtime·udiv(SB)  	/* one neg */
+	RSB	$0, Rq, RTMP
+out1:
+	MOVW	4(R13), Rq
+	MOVW	8(R13), Rr
+	MOVW	12(R13), Rs
+	MOVW	16(R13), RM
+	RET
+
+TEXT runtime·_mod(SB),NOSPLIT,$16-0
+	NO_LOCAL_POINTERS
+	MOVW	Rq, 4(R13)
+	MOVW	Rr, 8(R13)
+	MOVW	Rs, 12(R13)
+	MOVW	RM, 16(R13)
+	MOVW	Rn, Rr			/* numerator */
+	MOVW	g_m(g), Rq
+	MOVW	m_divmod(Rq), Rq	/* denominator */
+	CMP 	$0, Rq
+	RSB.LT	$0, Rq, Rq
+	CMP 	$0, Rr
+	BGE 	m1
+	RSB 	$0, Rr, Rr
+	BL  	runtime·udiv(SB)  	/* neg numerator */
+	RSB 	$0, Rr, RTMP
+	B   	out
+m1:
+	BL  	runtime·udiv(SB)  	/* pos numerator */
+	MOVW	Rr, RTMP
+out:
+	MOVW	4(R13), Rq
+	MOVW	8(R13), Rr
+	MOVW	12(R13), Rs
+	MOVW	16(R13), RM
+	RET
+
 // _mul64by32 and _div64by32 not implemented on arm
 TEXT runtime·_mul64by32(SB), NOSPLIT, $0
 	MOVW	$0, R0

test/fixedbugs/issue19507.dir/div_arm.s

+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+TEXT main·f(SB),0,$0-8
+	MOVW	x+0(FP), R1
+	MOVW	x+4(FP), R2
+	DIVU	R1, R2
+	DIV	R1, R2
+	MODU	R1, R2
+	MOD	R1, R2
+	RET

test/fixedbugs/issue19507.dir/main.go

+// +build arm
+
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Make sure we can compile assembly with DIV and MOD in it.
+// They get rewritten to runtime calls on GOARM=5.
+
+package main
+
+func f(x, y uint32)
+
+func main() {
+	f(5, 8)
+}

test/fixedbugs/issue19507.go

+// +build arm
+// builddir
+
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ignored

test/run.go

@@ -480,7 +480,7 @@ func (t *test) run() {
 		action = "rundir"
 	case "cmpout":
 		action = "run" // the run case already looks for <dir>/<test>.out files
-	case "compile", "compiledir", "build", "run", "buildrun", "runoutput", "rundir":
+	case "compile", "compiledir", "build", "builddir", "run", "buildrun", "runoutput", "rundir":
 		// nothing to do
 	case "errorcheckandrundir":
 		wantError = false // should be no error if also will run
@@ -706,6 +706,63 @@ func (t *test) run() {
 			t.err = err
 		}
 
+	case "builddir":
+		// Build an executable from all the .go and .s files in a subdirectory.
+		useTmp = true
+		longdir := filepath.Join(cwd, t.goDirName())
+		files, dirErr := ioutil.ReadDir(longdir)
+		if dirErr != nil {
+			t.err = dirErr
+			break
+		}
+		var gos []os.FileInfo
+		var asms []os.FileInfo
+		for _, file := range files {
+			switch filepath.Ext(file.Name()) {
+			case ".go":
+				gos = append(gos, file)
+			case ".s":
+				asms = append(asms, file)
+			}
+
+		}
+		var objs []string
+		cmd := []string{"go", "tool", "compile", "-e", "-D", ".", "-I", ".", "-o", "go.o"}
+		for _, file := range gos {
+			cmd = append(cmd, filepath.Join(longdir, file.Name()))
+		}
+		_, err := runcmd(cmd...)
+		if err != nil {
+			t.err = err
+			break
+		}
+		objs = append(objs, "go.o")
+		if len(asms) > 0 {
+			cmd = []string{"go", "tool", "asm", "-e", "-I", ".", "-o", "asm.o"}
+			for _, file := range asms {
+				cmd = append(cmd, filepath.Join(longdir, file.Name()))
+			}
+			_, err = runcmd(cmd...)
+			if err != nil {
+				t.err = err
+				break
+			}
+			objs = append(objs, "asm.o")
+		}
+		cmd = []string{"go", "tool", "pack", "c", "all.a"}
+		cmd = append(cmd, objs...)
+		_, err = runcmd(cmd...)
+		if err != nil {
+			t.err = err
+			break
+		}
+		cmd = []string{"go", "tool", "link", "all.a"}
+		_, err = runcmd(cmd...)
+		if err != nil {
+			t.err = err
+			break
+		}
+
 	case "buildrun": // build binary, then run binary, instead of go run. Useful for timeout tests where failure mode is infinite loop.
 		// TODO: not supported on NaCl
 		useTmp = true