[ARM] Only produce qadd8b under hasV6Ops

When compiling for a arm5te cpu from clang, the +dsp attribute is set.
This meant we could try and generate qadd8 instructions where we would
end up having no pattern. I've changed the condition here to be hasV6Ops
&& hasDSP, which is what other parts of ARMISelLowering seem to use for
similar instructions.

Fixed PR45677.

Differential Revision: https://reviews.llvm.org/D78877

(cherry picked from commit 8807139)

Author: davemgreen

llvm/lib/Target/ARM/ARMISelLowering.cpp

@@ -4549,7 +4549,7 @@ SDValue ARMTargetLowering::LowerUnsignedALUO(SDValue Op,
 static SDValue LowerSADDSUBSAT(SDValue Op, SelectionDAG &DAG,
                                const ARMSubtarget *Subtarget) {
   EVT VT = Op.getValueType();
-  if (!Subtarget->hasDSP())
+  if (!Subtarget->hasV6Ops() || !Subtarget->hasDSP())
     return SDValue();
   if (!VT.isSimple())
     return SDValue();

llvm/test/CodeGen/ARM/sadd_sat.ll

@@ -4,6 +4,7 @@
 ; RUN: llc < %s -mtriple=thumbv7em-none-eabi | FileCheck %s --check-prefix=CHECK-T2 --check-prefix=CHECK-T2DSP
 ; RUN: llc < %s -mtriple=armv5t-none-eabi | FileCheck %s --check-prefix=CHECK-ARM --check-prefix=CHECK-ARMNODPS
 ; RUN: llc < %s -mtriple=armv5te-none-eabi | FileCheck %s --check-prefix=CHECK-ARM --check-prefix=CHECK-ARMBASEDSP
+; RUN: llc < %s -mtriple=armv5te-none-eabi -mattr=+dsp | FileCheck %s --check-prefix=CHECK-ARM --check-prefix=CHECK-ARMBASEDSP
 ; RUN: llc < %s -mtriple=armv6-none-eabi | FileCheck %s --check-prefix=CHECK-ARM --check-prefix=CHECK-ARMDSP
 
 declare i4 @llvm.sadd.sat.i4(i4, i4)