emit add/sub registers instructions in integrated ARM assembler.

tests_lit/assembler/arm32/sub.ll

 ; Show that we know how to translate instruction sub.
-; TODO(kschimpf) Currently only know how to test subtract 1 from R0.
 

[Jim Stichnoth, 2015/10/16 21:30:09]

; REQUIRES: allow_dump

[Karl, 2015/10/17 20:00:41]

Done.

 ; NOTE: We use -O2 to get rid of memory stores.
 
 ; RUN: %p2i --filetype=asm -i %s --target=arm32 --args -O2 \
 ; RUN:   | FileCheck %s --check-prefix=ASM
 ; RUN: %p2i --filetype=iasm -i %s --target=arm32 --args -O2 \
 ; RUN:   | FileCheck %s --check-prefix=IASM
 
 define internal i32 @sub1FromR0(i32 %p) {
   %v = sub i32 %p, 1
   ret i32 %v
 }
 
 ; ASM-LABEL: sub1FromR0:
 ; ASM:  sub     r0, r0, #1
 ; ASM:  bx      lr
 
 ; IASM-LABEL: sub1FromR0:
 ; IASM:      .byte 0x1
 ; IASM-NEXT: .byte 0x0
 ; IASM-NEXT: .byte 0x40
 ; IASM-NEXT: .byte 0xe2
 
+
+define internal i32 @Sub2Regs(i32 %p1, i32 %p2) {
+  %v = sub i32 %p1, %p2
+  ret i32 %v
+}
+
+; ASM-LABEL: Sub2Regs:
+; ASM:       sub r0, r0, r1
+; ASM-NEXT:  bx lr
+
+; IASM-LABEL: Sub2Regs:
+
+; IASM:      .byte 0x1
+; IASM-NEXT: .byte 0x0
+; IASM-NEXT: .byte 0x40
+; IASM-NEXT: .byte 0xe0
+