Add translation of REV in ARM integrated assembler.

tests_lit/assembler/arm32/rev.ll

+; Show that we know how to translate rev (used in bswap).
+
+; NOTE: We use -O2 to get rid of memory stores.
+
+; REQUIRES: allow_dump
+
+; Compile using standalone assembler.
+; RUN: %p2i --filetype=asm -i %s --target=arm32 --args -O2 \
+; RUN:   | FileCheck %s --check-prefix=ASM
+
+; Show bytes in assembled standalone code.
+; RUN: %p2i --filetype=asm -i %s --target=arm32 --assemble --disassemble \
+; RUN:   --args -O2 | FileCheck %s --check-prefix=DIS
+
+; Compile using integrated assembler.
+; RUN: %p2i --filetype=iasm -i %s --target=arm32 --args -O2 \
+; RUN:   | FileCheck %s --check-prefix=IASM
+
+; Show bytes in assembled integrated code.
+; RUN: %p2i --filetype=iasm -i %s --target=arm32 --assemble --disassemble \
+; RUN:   --args -O2 | FileCheck %s --check-prefix=DIS
+
+declare i16 @llvm.bswap.i16(i16)
+
+define internal i32 @_Z10test_rev(i32 %a) {

[Jim Stichnoth, 2015/12/11 16:51:23]

Friendlier function name?

[Karl, 2015/12/11 17:32:41]

Done.

+; ASM-LABEL:_Z10test_rev:
+; DIS-LABEL:00000000 <_Z10test_rev>:
+; IASM-LABEL:_Z10test_rev:
+
+entry:
+; ASM-NEXT:.L_Z10test_rev$entry:
+; IASM-NEXT:.L_Z10test_rev$entry:
+
+  %a.arg_trunc = trunc i32 %a to i16
+  %v = tail call i16 @llvm.bswap.i16(i16 %a.arg_trunc)
+
+; ***** Example of rev instruction. *****
+; ASM-NEXT:     rev     r0, r0
+; DIS-NEXT:   0:        e6bf0f30
+; IASM-NEXT:    .byte 0x30
+; IASM-NEXT:    .byte 0xf
+; IASM-NEXT:    .byte 0xbf
+; IASM-NEXT:    .byte 0xe6
+
+; ASM-NEXT:     lsr     r0, r0, #16
+
+  %.ret_ext = zext i16 %v to i32
+  ret i32 %.ret_ext
+}