[llvm] [RISCV][GISel] Legalizer and register bank selection for G_JUMP_TABLE and G_BRJT (PR #71970)

[Michael Maitland via llvm-commits]

================
@@ -0,0 +1,121 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=riscv32 -mattr=+m -run-pass=legalizer %s -o - \
+# RUN: | FileCheck %s
+
+--- |
+  define i32 @jt_test(i32 %x) {
+  entry:
+    switch i32 %x, label %return [
+      i32 75, label %sw.bb
+      i32 34, label %sw.bb
+      i32 56, label %sw.bb
+      i32 35, label %sw.bb
+      i32 40, label %sw.bb
+      i32 4, label %sw.bb1
+      i32 5, label %sw.bb1
+      i32 6, label %sw.bb1
+    ]
+
+  sw.bb:                                            ; preds = %entry, %entry, %entry, %entry, %entry
+    %add = add nsw i32 %x, 42
+    br label %return
+
+  sw.bb1:                                           ; preds = %entry, %entry, %entry
+    %mul = mul nsw i32 %x, 3
+    br label %return
+
+  return:                                           ; preds = %sw.bb1, %sw.bb, %entry
+    %retval.0 = phi i32 [ %mul, %sw.bb1 ], [ %add, %sw.bb ], [ 0, %entry ]
+    ret i32 %retval.0
+  }
+
+...
+---
+name:            jt_test
+tracksRegLiveness: true
+jumpTable:
+  kind:            block-address
+  entries:
+    - id:              0
+      blocks:          [ '%bb.3', '%bb.3', '%bb.3', '%bb.4', '%bb.4', '%bb.4',
+                         '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4',
+                         '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4',
+                         '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4',
+                         '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4',
+                         '%bb.2', '%bb.2', '%bb.4', '%bb.4', '%bb.4', '%bb.4',
+                         '%bb.2', '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4',
+                         '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4',
+                         '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.2', '%bb.4',
+                         '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4',
+                         '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4',
+                         '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.4', '%bb.2' ]
+body:             |
+  ; CHECK-LABEL: name: jt_test
+  ; CHECK: bb.0.entry:
+  ; CHECK-NEXT:   successors: %bb.4(0x071c71c7), %bb.1(0x78e38e39)
+  ; CHECK-NEXT:   liveins: $x10
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[COPY:%[0-9]+]]:_(s32) = COPY $x10
+  ; CHECK-NEXT:   [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 71
+  ; CHECK-NEXT:   [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 3
+  ; CHECK-NEXT:   [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 42
+  ; CHECK-NEXT:   [[C3:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
+  ; CHECK-NEXT:   [[C4:%[0-9]+]]:_(s32) = G_CONSTANT i32 4
+  ; CHECK-NEXT:   [[SUB:%[0-9]+]]:_(s32) = G_SUB [[COPY]], [[C4]]
+  ; CHECK-NEXT:   [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ugt), [[SUB]](s32), [[C]]
+  ; CHECK-NEXT:   G_BRCOND [[ICMP]](s32), %bb.4
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.1.entry:
+  ; CHECK-NEXT:   successors: %bb.3(0x2d2d2d2d), %bb.4(0x07878787), %bb.2(0x4b4b4b4c)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[JUMP_TABLE:%[0-9]+]]:_(p0) = G_JUMP_TABLE %jump-table.0
+  ; CHECK-NEXT:   G_BRJT [[JUMP_TABLE]](p0), %jump-table.0, [[SUB]](s32)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.2.sw.bb:
+  ; CHECK-NEXT:   successors: %bb.4(0x80000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[ADD:%[0-9]+]]:_(s32) = nsw G_ADD [[COPY]], [[C2]]
+  ; CHECK-NEXT:   G_BR %bb.4
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.3.sw.bb1:
+  ; CHECK-NEXT:   successors: %bb.4(0x80000000)
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT:   [[MUL:%[0-9]+]]:_(s32) = nsw G_MUL [[COPY]], [[C1]]
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.4.return:
+  ; CHECK-NEXT:   [[PHI:%[0-9]+]]:_(s32) = G_PHI [[MUL]](s32), %bb.3, [[ADD]](s32), %bb.2, [[C3]](s32), %bb.0, [[C3]](s32), %bb.1
+  ; CHECK-NEXT:   $x10 = COPY [[PHI]](s32)
+  ; CHECK-NEXT:   PseudoRET implicit $x10
+  bb.1.entry:
+    successors: %bb.4(0x071c71c7), %bb.5(0x78e38e39)
----------------
michaelmaitland wrote:

Do we really need the branch probability data? It may make the test easier to read without it?

https://github.com/llvm/llvm-project/pull/71970