[RISCV] Add test cases for widening add/sub with mismatched extends. NFC (#166700)

These are test cases where we have an add and a sub with the same
operands. One operand is a sign extend and the other is a zero extend.

The sub can only form a vwsub.wv but because add is commutable, it could
form vwadd.wv or vwaddu.wv depending on which extend is removed. We want
to form vwadd.wv to match the sub so the vsext can be removed.

Depending on the order of the instructions and the operand order of the
add, we might form vwaddu.wv instead and no extends will be removed.

Author: topperc

llvm/test/CodeGen/RISCV/rvv/vscale-vw-web-simplification.ll

@@ -570,7 +570,83 @@ define <vscale x 2 x i32> @vwop_vscale_zext_i8i32_multiple_users(ptr %x, ptr %y,
   ret <vscale x 2 x i32> %i
 }
 
+define <vscale x 4 x i32> @mismatched_extend_sub_add(<vscale x 4 x i16> %x, <vscale x 4 x i16> %y) {
+; FOLDING-LABEL: mismatched_extend_sub_add:
+; FOLDING:       # %bb.0:
+; FOLDING-NEXT:    vsetvli a0, zero, e32, m2, ta, ma
+; FOLDING-NEXT:    vzext.vf2 v10, v8
+; FOLDING-NEXT:    vsetvli zero, zero, e16, m1, ta, ma
+; FOLDING-NEXT:    vwsub.wv v12, v10, v9
+; FOLDING-NEXT:    vwadd.wv v10, v10, v9
+; FOLDING-NEXT:    vsetvli zero, zero, e32, m2, ta, ma
+; FOLDING-NEXT:    vmul.vv v8, v12, v10
+; FOLDING-NEXT:    ret
+  %a = zext <vscale x 4 x i16> %x to <vscale x 4 x i32>
+  %b = sext <vscale x 4 x i16> %y to <vscale x 4 x i32>
+  %c = sub <vscale x 4 x i32> %a, %b
+  %d = add <vscale x 4 x i32> %a, %b
+  %e = mul <vscale x 4 x i32> %c, %d
+  ret <vscale x 4 x i32> %e
+}
+
+; FIXME: this should remove the vsext
+define <vscale x 4 x i32> @mismatched_extend_sub_add_commuted(<vscale x 4 x i16> %x, <vscale x 4 x i16> %y) {
+; FOLDING-LABEL: mismatched_extend_sub_add_commuted:
+; FOLDING:       # %bb.0:
+; FOLDING-NEXT:    vsetvli a0, zero, e32, m2, ta, ma
+; FOLDING-NEXT:    vzext.vf2 v10, v8
+; FOLDING-NEXT:    vsext.vf2 v12, v9
+; FOLDING-NEXT:    vsetvli zero, zero, e16, m1, ta, ma
+; FOLDING-NEXT:    vwsub.wv v10, v10, v9
+; FOLDING-NEXT:    vwaddu.wv v12, v12, v8
+; FOLDING-NEXT:    vsetvli zero, zero, e32, m2, ta, ma
+; FOLDING-NEXT:    vmul.vv v8, v10, v12
+; FOLDING-NEXT:    ret
+  %a = zext <vscale x 4 x i16> %x to <vscale x 4 x i32>
+  %b = sext <vscale x 4 x i16> %y to <vscale x 4 x i32>
+  %c = sub <vscale x 4 x i32> %a, %b
+  %d = add <vscale x 4 x i32> %b, %a
+  %e = mul <vscale x 4 x i32> %c, %d
+  ret <vscale x 4 x i32> %e
+}
 
+define <vscale x 4 x i32> @mismatched_extend_add_sub(<vscale x 4 x i16> %x, <vscale x 4 x i16> %y) {
+; FOLDING-LABEL: mismatched_extend_add_sub:
+; FOLDING:       # %bb.0:
+; FOLDING-NEXT:    vsetvli a0, zero, e32, m2, ta, ma
+; FOLDING-NEXT:    vzext.vf2 v10, v8
+; FOLDING-NEXT:    vsetvli zero, zero, e16, m1, ta, ma
+; FOLDING-NEXT:    vwadd.wv v12, v10, v9
+; FOLDING-NEXT:    vwsub.wv v10, v10, v9
+; FOLDING-NEXT:    vsetvli zero, zero, e32, m2, ta, ma
+; FOLDING-NEXT:    vmul.vv v8, v12, v10
+; FOLDING-NEXT:    ret
+  %a = zext <vscale x 4 x i16> %x to <vscale x 4 x i32>
+  %b = sext <vscale x 4 x i16> %y to <vscale x 4 x i32>
+  %c = add <vscale x 4 x i32> %a, %b
+  %d = sub <vscale x 4 x i32> %a, %b
+  %e = mul <vscale x 4 x i32> %c, %d
+  ret <vscale x 4 x i32> %e
+}
+
+define <vscale x 4 x i32> @mismatched_extend_add_sub_commuted(<vscale x 4 x i16> %x, <vscale x 4 x i16> %y) {
+; FOLDING-LABEL: mismatched_extend_add_sub_commuted:
+; FOLDING:       # %bb.0:
+; FOLDING-NEXT:    vsetvli a0, zero, e32, m2, ta, ma
+; FOLDING-NEXT:    vzext.vf2 v10, v8
+; FOLDING-NEXT:    vsetvli zero, zero, e16, m1, ta, ma
+; FOLDING-NEXT:    vwadd.wv v12, v10, v9
+; FOLDING-NEXT:    vwsub.wv v10, v10, v9
+; FOLDING-NEXT:    vsetvli zero, zero, e32, m2, ta, ma
+; FOLDING-NEXT:    vmul.vv v8, v12, v10
+; FOLDING-NEXT:    ret
+  %a = zext <vscale x 4 x i16> %x to <vscale x 4 x i32>
+  %b = sext <vscale x 4 x i16> %y to <vscale x 4 x i32>
+  %c = add <vscale x 4 x i32> %a, %b
+  %d = sub <vscale x 4 x i32> %a, %b
+  %e = mul <vscale x 4 x i32> %c, %d
+  ret <vscale x 4 x i32> %e
+}
 
 ;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
 ; RV32: {{.*}}