cmd/asm: handle CMPF and CMPD on ARM

These instructions are special cases that were missed in the translation.
The second argument must go into the Reg field not the To field.

Fixes #12458

For Go 1.5.1

Change-Id: Iad57c60c7e38e3bcfafda483ed5037ce670e8816
Reviewed-on: https://go-review.googlesource.com/14183Reviewed-by: Dave Cheney <dave@cheney.net>
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/asm/internal/arch/arm.go

@@ -121,6 +121,15 @@ func IsARMMRC(op int) bool {
 	return false
 }
 
+// IsARMFloatCmp reports whether the op is a floating comparison instruction.
+func IsARMFloatCmp(op int) bool {
+	switch op {
+	case arm.ACMPF, arm.ACMPD:
+		return true
+	}
+	return false
+}
+
 // ARMMRCOffset implements the peculiar encoding of the MRC and MCR instructions.
 // The difference between MRC and MCR is represented by a bit high in the word, not
 // in the usual way by the opcode itself. Asm must use AMRC for both instructions, so

src/cmd/asm/internal/asm/asm.go

@@ -469,6 +469,11 @@ func (p *Parser) asmInstruction(op int, cond string, a []obj.Addr) {
 				}
 				p.errorf("unrecognized addressing for %s", obj.Aconv(op))
 			}
+			if arch.IsARMFloatCmp(op) {
+				prog.From = a[0]
+				prog.Reg = p.getRegister(prog, op, &a[1])
+				break
+			}
 		} else if p.arch.Thechar == '7' && arch.IsARM64CMP(op) {
 			prog.From = a[0]
 			prog.Reg = p.getRegister(prog, op, &a[1])

src/cmd/asm/internal/asm/testdata/arm.out

@@ -55,4 +55,6 @@
 273 00055 (testdata/arm.s:273)	CALL	foo(SB)
 274 00056 (testdata/arm.s:274)	JMP	foo(SB)
 275 00057 (testdata/arm.s:275)	CALL	foo(SB)
-284 00058 (testdata/arm.s:284)	END
+278 00058 (testdata/arm.s:278)	CMPF	F1, F2
+279 00059 (testdata/arm.s:279)	CMPD	F1, F2
+288 00060 (testdata/arm.s:288)	END

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

@@ -274,6 +274,10 @@ TEXT	foo(SB), 0, $0
 	JMP	foo(SB)
 	CALL	foo(SB)
 
+// CMPF and CMPD are special.
+	CMPF F1, F2
+	CMPD F1, F2
+
 //
 // END
 //