[WebAssembly] Convert stackified IMPLICIT_DEF into constant 0.

Since IMPLIFIT_DEF instructions are omitted in the output, when the output
of an IMPLICIT_DEF instruction is stackified, the resulting register lacks
an explicit push, leading to a push/pop mismatch. Fix this by converting
such IMPLICIT_DEFs into CONST_I32 0 instructions so that they have explicit
pushes.

llvm-svn: 286274

1 files changed, 50 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/WebAssembly/implicit-def.ll b/llvm/test/CodeGen/WebAssembly/implicit-def.ll
new file mode 100644
index 00000000000..01ee171b449
--- /dev/null
+++ b/llvm/test/CodeGen/WebAssembly/implicit-def.ll
@@ -0,0 +1,50 @@
+; RUN: llc -o - %s | FileCheck %s
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+; Test that stackified IMPLICIT_DEF instructions are converted into
+; CONST_I32 to provide an explicit push.
+
+; CHECK:      br_if 2,
+; CHECK:      i32.const $push[[L0:[0-9]+]]=, 0{{$}}
+; CHECK-NEXT: return $pop[[L0]]{{$}}
+define i1 @f() {
+  %a = xor i1 0, 0
+  switch i1 %a, label %C [
+    i1 0, label %A
+    i1 1, label %B
+  ]
+
+A:
+  %b = xor i1 0, 0
+  br label %X
+
+B:
+  %c = xor i1 0, 0
+  br i1 %c, label %D, label %X
+
+C:
+  %d = icmp slt i32 0, 0
+  br i1 %d, label %G, label %F
+
+D:
+  %e = xor i1 0, 0
+  br i1 %e, label %E, label %X
+
+E:
+  %f = xor i1 0, 0
+  br label %X
+
+F:
+  %g = xor i1 0, 0
+  br label %G
+
+G:
+  %h = phi i1 [ undef, %C ], [ false, %F ]
+  br label %X
+
+X:
+  %i = phi i1 [ true, %A ], [ true, %B ], [ true, %D ], [ true, %E ], [ %h, %G ]
+  ret i1 %i
+}
+