runtime: correct fault for 16-bit divide on Leopard

R=r
CC=golang-dev
https://golang.org/cl/1703041

src/pkg/runtime/darwin/386/signal.c

@@ -54,7 +54,9 @@ sighandler(int32 sig, Siginfo *info, void *context)
 		// Not necessary in Snow Leopard (si_code will be != 0).
 		if(sig == SIGFPE && info->si_code == 0) {
 			pc = (byte*)r->eip;
-			if(pc[0] == 0xF7)
+			if(pc[0] == 0x66)	// 16-bit instruction prefix
+				pc++;
+			if(pc[0] == 0xF6 || pc[0] == 0xF7)
 				info->si_code = FPE_INTDIV;
 		}
 		

src/pkg/runtime/darwin/amd64/signal.c

@@ -63,7 +63,9 @@ sighandler(int32 sig, Siginfo *info, void *context)
 			pc = (byte*)r->rip;
 			if((pc[0]&0xF0) == 0x40)	// 64-bit REX prefix
 				pc++;
-			if(pc[0] == 0xF7)
+			else if(pc[0] == 0x66)	// 16-bit instruction prefix
+				pc++;
+			if(pc[0] == 0xF6 || pc[0] == 0xF7)
 				info->si_code = FPE_INTDIV;
 		}
 		

test/golden.out

@@ -54,10 +54,6 @@ FAIL
 Hello World!
 
 =========== ./zerodivide.go
-int16 0/0: expected "divide"; got "runtime error: floating point error"
-int16 1/0: expected "divide"; got "runtime error: floating point error"
-uint16 0/0: expected "divide"; got "runtime error: floating point error"
-uint16 1/0: expected "divide"; got "runtime error: floating point error"
 complex 0/0: expected no error; got "runtime error: complex divide by zero"
 complex64 0/0: expected no error; got "runtime error: complex divide by zero"
 complex128 0/0: expected no error; got "runtime error: complex divide by zero"

test/zerodivide.go

@@ -56,30 +56,26 @@ func use(v interface{}) {
 var errorTests = []ErrorTest{
 	// All integer divide by zero should error.
 	ErrorTest{ "int 0/0", func() { use(i/j) }, "divide", },
-// TODO commented out: fails in 8g.
-//	ErrorTest{ "int8 0/0", func() { use(i8/j8) }, "divide", },
+	ErrorTest{ "int8 0/0", func() { use(i8/j8) }, "divide", },
 	ErrorTest{ "int16 0/0", func() { use(i16/j16) }, "divide", },
 	ErrorTest{ "int32 0/0", func() { use(i32/j32) }, "divide", },
 	ErrorTest{ "int64 0/0", func() { use(i64/j64) }, "divide", },
 
 	ErrorTest{ "int 1/0", func() { use(k/j) }, "divide", },
-// TODO commented out: fails in 8g.
-//	ErrorTest{ "int8 1/0", func() { use(k8/j8) }, "divide", },
+	ErrorTest{ "int8 1/0", func() { use(k8/j8) }, "divide", },
 	ErrorTest{ "int16 1/0", func() { use(k16/j16) }, "divide", },
 	ErrorTest{ "int32 1/0", func() { use(k32/j32) }, "divide", },
 	ErrorTest{ "int64 1/0", func() { use(k64/j64) }, "divide", },
 
 	ErrorTest{ "uint 0/0", func() { use(u/v) }, "divide", },
-// TODO commented out: fails in 8g.
-//	ErrorTest{ "uint8 0/0", func() { use(u8/v8) }, "divide", },
+	ErrorTest{ "uint8 0/0", func() { use(u8/v8) }, "divide", },
 	ErrorTest{ "uint16 0/0", func() { use(u16/v16) }, "divide", },
 	ErrorTest{ "uint32 0/0", func() { use(u32/v32) }, "divide", },
 	ErrorTest{ "uint64 0/0", func() { use(u64/v64) }, "divide", },
 	ErrorTest{ "uintptr 0/0", func() { use(up/vp) }, "divide", },
 
 	ErrorTest{ "uint 1/0", func() { use(w/v) }, "divide", },
-// TODO commented out: fails in 8g.
-//	ErrorTest{ "uint8 1/0", func() { use(w8/v8) }, "divide", },
+	ErrorTest{ "uint8 1/0", func() { use(w8/v8) }, "divide", },
 	ErrorTest{ "uint16 1/0", func() { use(w16/v16) }, "divide", },
 	ErrorTest{ "uint32 1/0", func() { use(w32/v32) }, "divide", },
 	ErrorTest{ "uint64 1/0", func() { use(w64/v64) }, "divide", },