[SelectionDAG] Add SPLAT_VECTOR to SelectionDAG::isConstantFPBuildVectorOrConstantFP.

Matches what is done for the int version.

Reviewed By: sdesmalen

Differential Revision: https://reviews.llvm.org/D119793

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -11117,6 +11117,10 @@ SDNode *SelectionDAG::isConstantFPBuildVectorOrConstantFP(SDValue N) const {
   if (ISD::isBuildVectorOfConstantFPSDNodes(N.getNode()))
     return N.getNode();
 
+  if ((N.getOpcode() == ISD::SPLAT_VECTOR) &&
+      isa<ConstantFPSDNode>(N.getOperand(0)))
+    return N.getNode();
+
   return nullptr;
 }
 

llvm/test/CodeGen/RISCV/rvv/combine-splats.ll

@@ -109,3 +109,25 @@ define <vscale x 8 x i16> @combine_vec_lshr_lshr(<vscale x 8 x i16> %x) {
   %v2 = lshr <vscale x 8 x i16> %v1, %splat2
   ret <vscale x 8 x i16> %v2
 }
+
+; fold (fmul x, 1.0) -> x
+define <vscale x 2 x float> @combine_fmul_one(<vscale x 2 x float> %x) {
+; CHECK-LABEL: combine_fmul_one:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    ret
+  %ins = insertelement <vscale x 2 x float> poison, float 1.0, i32 0
+  %splat = shufflevector <vscale x 2 x float> %ins, <vscale x 2 x float> poison, <vscale x 2 x i32> zeroinitializer
+  %v = fmul <vscale x 2 x float> %x, %splat
+  ret <vscale x 2 x float> %v
+}
+
+; fold (fmul 1.0, x) -> x
+define <vscale x 2 x float> @combine_fmul_one_commuted(<vscale x 2 x float> %x) {
+; CHECK-LABEL: combine_fmul_one_commuted:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    ret
+  %ins = insertelement <vscale x 2 x float> poison, float 1.0, i32 0
+  %splat = shufflevector <vscale x 2 x float> %ins, <vscale x 2 x float> poison, <vscale x 2 x i32> zeroinitializer
+  %v = fmul <vscale x 2 x float> %splat, %x
+  ret <vscale x 2 x float> %v
+}