ARM64: print canonical syntax for add/sub (imm) instructions.

Since these instructions only accept a 12-bit immediate, possibly shifted left
by 12, the canonical syntax used by the architecture reference manual is "#N {,
lsl #12 }". We should accept an immediate that has already been shifted, (e.g.

Also, print a comment giving the full addend since it can be helpful.

llvm-svn: 207633

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/lib/Target/ARM64/InstPrinter/ARM64InstPrinter.cpp b/llvm/lib/Target/ARM64/InstPrinter/ARM64InstPrinter.cpp
index a07b7be00d2..875c758b1ad 100644
--- a/llvm/lib/Target/ARM64/InstPrinter/ARM64InstPrinter.cpp
+++ b/llvm/lib/Target/ARM64/InstPrinter/ARM64InstPrinter.cpp
@@ -1104,10 +1104,12 @@ void ARM64InstPrinter::printAddSubImm(const MCInst *MI, unsigned OpNum,
     assert(Val == MO.getImm() && "Add/sub immediate out of range!");
     unsigned Shift =
         ARM64_AM::getShiftValue(MI->getOperand(OpNum + 1).getImm());
-    O << '#' << (Val << Shift);
-    // Distinguish "0, lsl #12" from "0, lsl #0".
-    if (Val == 0 && Shift != 0)
+    O << '#' << Val;
+    if (Shift != 0)
       printShifter(MI, OpNum + 1, O);
+
+    if (CommentStream)
+      *CommentStream << "=#" << (Val << Shift) << '\n';
   } else {
     assert(MO.isExpr() && "Unexpected operand type!");
     O << *MO.getExpr();