[Intrinsic] Signed and Unsigned Saturation Subtraction Intirnsics

Add an intrinsic that takes 2 integers and perform saturation subtraction on
them.

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

Differential Revision: https://reviews.llvm.org/D53783

llvm-svn: 345512

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index 715112edc17..30887e2d5f8 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -612,6 +612,8 @@ void TargetLoweringBase::initActions() {
     setOperationAction(ISD::ABS, VT, Expand);
     setOperationAction(ISD::SADDSAT, VT, Expand);
     setOperationAction(ISD::UADDSAT, VT, Expand);
+    setOperationAction(ISD::SSUBSAT, VT, Expand);
+    setOperationAction(ISD::USUBSAT, VT, Expand);
 
     // Overflow operations default to expand
     setOperationAction(ISD::SADDO, VT, Expand);