let PrintMethod = "printBrList";
}
-// TODO: SelectionDAG's lowering insists on using a pointer as the index for
-// jump tables, so in practice we don't ever use BR_TABLE_I64 in wasm32 mode
-// currently.
-let isTerminator = 1, hasCtrlDep = 1, isBarrier = 1 in {
+// Duplicating a BR_TABLE is almost never a good idea. In particular, it can
+// lead to some nasty irreducibility due to tail merging when the br_table is in
+// a loop.
+let isTerminator = 1, hasCtrlDep = 1, isBarrier = 1, isNotDuplicable = 1 in {
+
defm BR_TABLE_I32 : I<(outs), (ins I32:$index, variable_ops),
(outs), (ins brlist:$brl),
[(WebAssemblybr_table I32:$index)],
"br_table \t$index", "br_table \t$brl",
0x0e>;
+// TODO: SelectionDAG's lowering insists on using a pointer as the index for
+// jump tables, so in practice we don't ever use BR_TABLE_I64 in wasm32 mode
+// currently.
defm BR_TABLE_I64 : I<(outs), (ins I64:$index, variable_ops),
(outs), (ins brlist:$brl),
[(WebAssemblybr_table I64:$index)],
"br_table \t$index", "br_table \t$brl",
0x0e>;
-} // isTerminator = 1, hasCtrlDep = 1, isBarrier = 1
+} // isTerminator = 1, hasCtrlDep = 1, isBarrier = 1, isNotDuplicable = 1
// This is technically a control-flow instruction, since all it affects is the
// IP.
; Just check the barest skeleton of the structure
; CHECK-LABEL: test1:
-; CHECK: block
-; CHECK: block
-; CHECK: block
-; CHECK: block
; CHECK: i32.load
; CHECK: i32.load
-; CHECK: i32.const
-; CHECK: i32.add $push[[DEST:.+]]=
-; CHECK: br_table $pop[[DEST]]
-; CHECK: end_block
-; CHECK: end_block
-; CHECK: end_block
-; CHECK: end_block
; CHECK: loop
; CHECK: block
; CHECK: block
; CHECK: block
; CHECK: block
-; CHECK: br_table ${{[^,]+}}, 0, 1, 2, 2
-; CHECK: end_block
-; CHECK: end_block
-; CHECK: end_block
-; CHECK: block
-; CHECK: block
-; CHECK: block
; CHECK: br_table ${{[^,]+}}, 1, 2, 0
; CHECK: end_block
; CHECK: end_block
; CHECK: end_block
+; CHECK: end_block
+; CHECK: br
; CHECK: end_loop
+; CHECK: end_function
; CHECK: test1.targets:
; CHECK-NEXT: .int32
; CHECK-NEXT: .int32
--- /dev/null
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs | FileCheck %s
+
+;; Test that a small but nontrivial switch in a loop (like in a
+;; bytecode interpreter) lowers reasonably without any irreducible
+;; control flow being introduced.
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32"
+
+declare void @a(i32*)
+declare void @b(i32*)
+
+; CHECK-LABEL: switch_in_loop:
+; CHECK-NEXT: .functype switch_in_loop (i32, i32) -> (i32)
+; CHECK: global.get __stack_pointer
+; CHECK: global.set __stack_pointer
+; CHECK: block
+; CHECK: br_if 0
+; CHECK: .LBB0_2:
+; CHECK: loop
+; CHECK: block
+; CHECK: block
+; CHECK: block
+; CHECK: br_table {0, 1, 2}
+; CHECK: .LBB0_3:
+; CHECK: end_block
+; CHECK: call a
+; CHECK: br 1
+; CHECK: .LBB0_4:
+; CHECK: end_block
+; CHECK: call b
+; CHECK: .LBB0_5:
+; CHECK: end_block
+; CHECK: br_if 0
+; CHECK: end_loop
+; CHECK: .LBB0_7:
+; CHECK: end_block
+; CHECK: global.set __stack_pointer
+; CHECK: end_function
+define i32 @switch_in_loop(i32* %ops, i32 %len) {
+entry:
+ %res = alloca i32
+ %0 = bitcast i32* %res to i8*
+ store i32 0, i32* %res
+ %cmp6 = icmp sgt i32 %len, 0
+ br i1 %cmp6, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup.loopexit: ; preds = %sw.epilog
+ %.pre = load i32, i32* %res
+ br label %for.cond.cleanup
+
+for.cond.cleanup: ; preds = %for.cond.cleanup.loopexit, %entry
+ %1 = phi i32 [ %.pre, %for.cond.cleanup.loopexit ], [ 0, %entry ]
+ ret i32 %1
+
+for.body: ; preds = %entry, %sw.epilog
+ %i.07 = phi i32 [ %inc, %sw.epilog ], [ 0, %entry ]
+ %arrayidx = getelementptr inbounds i32, i32* %ops, i32 %i.07
+ %2 = load i32, i32* %arrayidx
+ switch i32 %2, label %sw.epilog [
+ i32 0, label %sw.bb
+ i32 1, label %sw.bb1
+ ]
+
+sw.bb: ; preds = %for.body
+ call void @a(i32* nonnull %res)
+ br label %sw.epilog
+
+sw.bb1: ; preds = %for.body
+ call void @b(i32* nonnull %res)
+ br label %sw.epilog
+
+sw.epilog: ; preds = %for.body, %sw.bb1, %sw.bb
+ %inc = add nuw nsw i32 %i.07, 1
+ %exitcond = icmp eq i32 %inc, %len
+ br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body
+}