[SystemZ] Make better use of VGEF/VGEG

Current code in SystemZDAGToDAGISel::tryGather refuses to perform
any transformation if the Load SDNode has more than one use.  This
(erronously) counts uses of the chain result, which prevents the
optimization in many cases unnecessarily.  Fixed by this patch.

llvm-svn: 349748

Author: uweigand

llvm/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp

@@ -1147,7 +1147,7 @@ bool SystemZDAGToDAGISel::tryGather(SDNode *N, unsigned Opcode) {
     return false;
 
   auto *Load = dyn_cast<LoadSDNode>(N->getOperand(1));
-  if (!Load || !Load->hasOneUse())
+  if (!Load || !Load->hasNUsesOfValue(1, 0))
     return false;
   if (Load->getMemoryVT().getSizeInBits() !=
       Load->getValueType(0).getSizeInBits())

llvm/test/CodeGen/SystemZ/vec-move-08.ll

@@ -442,3 +442,35 @@ define <2 x double> @f39(<2 x double> %val, <2 x i64> %index, i64 %base) {
   %ret = insertelement <2 x double> %val, double %element, i32 1
   ret <2 x double> %ret
 }
+
+; Test a v4i32 gather where the load is chained.
+define void @f40(<4 x i32> %val, <4 x i32> %index, i64 %base, <4 x i32> *%res) {
+; CHECK-LABEL: f40:
+; CHECK: vgef %v24, 0(%v26,%r2), 1
+; CHECK: vst %v24, 0(%r3)
+; CHECK: br %r14
+  %elem = extractelement <4 x i32> %index, i32 1
+  %ext = zext i32 %elem to i64
+  %add = add i64 %base, %ext
+  %ptr = inttoptr i64 %add to i32 *
+  %element = load i32, i32 *%ptr
+  %ret = insertelement <4 x i32> %val, i32 %element, i32 1
+  store <4 x i32> %ret, <4 x i32> *%res
+  ret void
+}
+
+; Test a v2i64 gather where the load is chained.
+define void @f41(<2 x i64> %val, <2 x i64> %index, i64 %base, <2 x i64> *%res) {
+; CHECK-LABEL: f41:
+; CHECK: vgeg %v24, 0(%v26,%r2), 1
+; CHECK: vst %v24, 0(%r3)
+; CHECK: br %r14
+  %elem = extractelement <2 x i64> %index, i32 1
+  %add = add i64 %base, %elem
+  %ptr = inttoptr i64 %add to i64 *
+  %element = load i64, i64 *%ptr
+  %ret = insertelement <2 x i64> %val, i64 %element, i32 1
+  store <2 x i64> %ret, <2 x i64> *%res
+  ret void
+}
+