[llvm] [RISCV][GISel] Add ISel support for SHXADD_UW and SLLI.UW (PR #69972)

[Craig Topper via llvm-commits]

================
@@ -150,3 +150,78 @@ body:             |
     %6:gprb(s64) = G_ADD %5, %1
     $x10 = COPY %6(s64)
 ...
+---
+name:            shXadd_uw_complex_shl_and
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.0.entry:
+    liveins: $x10, $x11
+
+    ; CHECK-LABEL: name: shXadd_uw_complex_shl_and
+    ; CHECK: liveins: $x10, $x11
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:gpr = COPY $x10
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:gpr = COPY $x11
+    ; CHECK-NEXT: [[SLLI:%[0-9]+]]:gpr = SLLI [[COPY]], 1
+    ; CHECK-NEXT: [[SH2ADD_UW:%[0-9]+]]:gpr = SH2ADD_UW [[SLLI]], [[COPY1]]
+    ; CHECK-NEXT: $x10 = COPY [[SH2ADD_UW]]
+    %0:gprb(s64) = COPY $x10
+    %1:gprb(s64) = COPY $x11
+
+    %2:gprb(s64) = G_CONSTANT i64 3
+    %3:gprb(s64) = G_SHL %0, %2
+    %4:gprb(s64) = G_CONSTANT i64 17179869183
+    %5:gprb(s64) = G_AND %3, %4
+
+    %6:gprb(s64) = G_ADD %5, %1
+    $x10 = COPY %6(s64)
+...
+---
+name:            slli_uw
----------------
topperc wrote:

I think we also need patterns for (shl (i64 (zext (i32 X))), C). SelectionDAG doesn't have that case since i32 isn't a legal type on RV64 there.

https://github.com/llvm/llvm-project/pull/69972