[Intrinsic] Add the llvm.umul.fix.sat intrinsic

Summary:
Add an intrinsic that takes 2 unsigned integers with
the scale of them provided as the third argument and
performs fixed point multiplication on them. The
result is saturated and clamped between the largest and
smallest representable values of the first 2 operands.

This is a part of implementing fixed point arithmetic
in clang where some of the more complex operations
will be implemented as intrinsics.

Patch by: leonardchan, bjope

Reviewers: RKSimon, craig.topper, bevinh, leonardchan, lebedev.ri, spatel

Reviewed By: leonardchan

Subscribers: ychen, wuzish, nemanjai, MaskRay, jsji, jdoerfert, Ka-Ka, hiraditya, rjmccall, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D57836

llvm-svn: 371308

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 601d42bd07c..077339a346c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -6317,6 +6317,14 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
                              Op3));
     return;
   }
+  case Intrinsic::umul_fix_sat: {
+    SDValue Op1 = getValue(I.getArgOperand(0));
+    SDValue Op2 = getValue(I.getArgOperand(1));
+    SDValue Op3 = getValue(I.getArgOperand(2));
+    setValue(&I, DAG.getNode(ISD::UMULFIXSAT, sdl, Op1.getValueType(), Op1, Op2,
+                             Op3));
+    return;
+  }
   case Intrinsic::stacksave: {
     SDValue Op = getRoot();
     Res = DAG.getNode(