[RISCV] Add isel pattern to turn (or (zext X), Y) into add.uw when X and Y are disjoint.

Improve code for -riscv-experimental-rv64-legal-i32.

Author: topperc

llvm/lib/Target/RISCV/RISCVInstrInfoZb.td

@@ -854,6 +854,9 @@ def : Pat<(i64 (add_non_imm12 (zext GPR:$rs1), GPR:$rs2)),
           (ADD_UW GPR:$rs1, GPR:$rs2)>;
 def : Pat<(zext GPR:$src), (ADD_UW GPR:$src, (XLenVT X0))>;
 
+def : Pat<(i64 (or_is_add_non_imm12 (zext GPR:$rs1), GPR:$rs2)),
+          (ADD_UW GPR:$rs1, GPR:$rs2)>;
+
 foreach i = {1,2,3} in {
   defvar shxadd = !cast<Instruction>("SH"#i#"ADD");
   def : Pat<(i32 (add_non_imm12 (shl GPR:$rs1, (i64 i)), GPR:$rs2)),

llvm/test/CodeGen/RISCV/rv64-legal-i32/rv64zba.ll

@@ -1829,3 +1829,71 @@ define i64 @shl_31_sh3add(ptr %0, i32 signext %1) {
   %6 = load i64, ptr %5, align 8
   ret i64 %6
 }
+
+define i64 @pack_i64(i64 %a, i64 %b) nounwind {
+; RV64I-LABEL: pack_i64:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a0, a0, 32
+; RV64I-NEXT:    srli a0, a0, 32
+; RV64I-NEXT:    slli a1, a1, 32
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    ret
+;
+; RV64ZBA-LABEL: pack_i64:
+; RV64ZBA:       # %bb.0:
+; RV64ZBA-NEXT:    slli a1, a1, 32
+; RV64ZBA-NEXT:    add.uw a0, a0, a1
+; RV64ZBA-NEXT:    ret
+  %shl = and i64 %a, 4294967295
+  %shl1 = shl i64 %b, 32
+  %or = or i64 %shl1, %shl
+  ret i64 %or
+}
+
+define i64 @pack_i64_2(i32 signext %a, i32 signext %b) nounwind {
+; RV64I-LABEL: pack_i64_2:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a0, a0, 32
+; RV64I-NEXT:    srli a0, a0, 32
+; RV64I-NEXT:    slli a1, a1, 32
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    ret
+;
+; RV64ZBA-LABEL: pack_i64_2:
+; RV64ZBA:       # %bb.0:
+; RV64ZBA-NEXT:    slli a1, a1, 32
+; RV64ZBA-NEXT:    add.uw a0, a0, a1
+; RV64ZBA-NEXT:    ret
+  %zexta = zext i32 %a to i64
+  %zextb = zext i32 %b to i64
+  %shl1 = shl i64 %zextb, 32
+  %or = or i64 %shl1, %zexta
+  ret i64 %or
+}
+
+define i64 @pack_i64_3(i32 signext %a, i32 signext %b) nounwind {
+; RV64I-LABEL: pack_i64_3:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    addi a0, a0, 1
+; RV64I-NEXT:    addi a1, a1, 1
+; RV64I-NEXT:    slli a0, a0, 32
+; RV64I-NEXT:    srli a0, a0, 32
+; RV64I-NEXT:    slli a1, a1, 32
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    ret
+;
+; RV64ZBA-LABEL: pack_i64_3:
+; RV64ZBA:       # %bb.0:
+; RV64ZBA-NEXT:    addi a0, a0, 1
+; RV64ZBA-NEXT:    addi a1, a1, 1
+; RV64ZBA-NEXT:    slli a1, a1, 32
+; RV64ZBA-NEXT:    add.uw a0, a0, a1
+; RV64ZBA-NEXT:    ret
+  %adda = add i32 %a, 1
+  %addb = add i32 %b, 1
+  %zexta = zext i32 %adda to i64
+  %zextb = zext i32 %addb to i64
+  %shl1 = shl i64 %zextb, 32
+  %or = or i64 %shl1, %zexta
+  ret i64 %or
+}