[ARM] Add <saturate> operand to SQRSHRL and UQRSHLL

Summary:
According to the new Armv8-M specification
https://static.docs.arm.com/ddi0553/bh/DDI0553B_h_armv8m_arm.pdf the
instructions SQRSHRL and UQRSHLL now have an additional immediate
operand <saturate>. The new assembly syntax is:

SQRSHRL<c> RdaLo, RdaHi, #<saturate>, Rm
UQRSHLL<c> RdaLo, RdaHi, #<saturate>, Rm

where <saturate> can be either 64 (the existing behavior) or 48, in
that case the result is saturated to 48 bits.

The new operand is encoded as follows:
  #64 Encoded as sat = 0
  #48 Encoded as sat = 1
sat is bit 7 of the instruction bit pattern.

This patch adds a new assembler operand class MveSaturateOperand which
implements parsing and encoding. Decoding is implemented in
DecodeMVEOverlappingLongShift.

Reviewers: ostannard, simon_tatham, t.p.northover, samparker, dmgreen, SjoerdMeijer

Reviewed By: simon_tatham

Subscribers: javed.absar, kristof.beyls, hiraditya, pbarrio, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64810

llvm-svn: 366555

2 files changed, 10 insertions, 1 deletions

diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMInstPrinter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMInstPrinter.cpp
index 45be1ee9634..30b82faa0ed 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMInstPrinter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMInstPrinter.cpp
@@ -1676,3 +1676,11 @@ void ARMInstPrinter::printExpandedImmOperand(const MCInst *MI, unsigned OpNum,
   O.write_hex(Val);
   O << markup(">");
 }
+
+void ARMInstPrinter::printMveSaturateOp(const MCInst *MI, unsigned OpNum,
+                                        const MCSubtargetInfo &STI,
+                                        raw_ostream &O) {
+  uint32_t Val = MI->getOperand(OpNum).getImm();
+  assert(Val <= 1 && "Invalid MVE saturate operand");
+  O << "#" << (Val == 1 ? 48 : 64);
+}
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMInstPrinter.h b/llvm/lib/Target/ARM/MCTargetDesc/ARMInstPrinter.h
index 69026956b60..7b02198d02e 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMInstPrinter.h
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMInstPrinter.h
@@ -262,7 +262,8 @@ public:
                                 const MCSubtargetInfo &STI, raw_ostream &O);
   void printExpandedImmOperand(const MCInst *MI, unsigned OpNum,
                                const MCSubtargetInfo &STI, raw_ostream &O);
-
+  void printMveSaturateOp(const MCInst *MI, unsigned OpNum,
+                         const MCSubtargetInfo &STI, raw_ostream &O);
 private:
   unsigned DefaultAltIdx = ARM::NoRegAltName;
 };