[WebAssembly] Split separate component LiveIntervals for TEEs

llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp

@@ -510,10 +510,11 @@ static unsigned getTeeOpcode(const TargetRegisterClass *RC) {
 
 // Shrink LI to its uses, cleaning up LI.
 static void shrinkToUses(LiveInterval &LI, LiveIntervals &LIS) {
-  if (LIS.shrinkToUses(&LI)) {
-    SmallVector<LiveInterval *, 4> SplitLIs;
-    LIS.splitSeparateComponents(LI, SplitLIs);
-  }
+  LIS.shrinkToUses(&LI);
+  // In case the register's live interval now has multiple unconnected
+  // components, split them into multiple registers.
+  SmallVector<LiveInterval *, 4> SplitLIs;
+  LIS.splitSeparateComponents(LI, SplitLIs);
 }
 
 /// A single-use def in the same block with no intervening memory or register

llvm/test/CodeGen/WebAssembly/tee-live-intervals.mir

@@ -0,0 +1,41 @@
+# RUN: llc -mtriple=wasm32-unknown-unknown -run-pass wasm-reg-stackify -verify-machineinstrs %s -o -
+
+# TEE generation in RegStackify can create virtual registers with LiveIntervals
+# with multiple disconnected segments, which is invalid in MachineVerifier. In
+# this test, '%0 = CALL @foo' will become a CALL and a TEE, which creates
+# unconnected split segments. This should be later split into multiple
+# registers. This test should not crash with -verify-machineinstrs, which checks
+# whether all segments within a register is connected. See ??? for the detailed
+# explanation.
+
+--- |
+  target triple = "wasm32-unknown-unknown"
+
+  declare ptr @foo(ptr returned)
+  define void @tee_live_intervals_test() {
+    ret void
+  }
+...
+---
+name: tee_live_intervals_test
+liveins:
+  - { reg: '$arguments' }
+tracksRegLiveness: true
+body: |
+  bb.0:
+    liveins: $arguments
+    successors: %bb.1, %bb.2
+    %0:i32 = ARGUMENT_i32 0, implicit $arguments
+    %1:i32 = CONST_I32 0, implicit-def dead $arguments
+    BR_IF %bb.2, %1:i32, implicit-def dead $arguments
+
+  bb.1:
+  ; predecessors: %bb.0
+    %0:i32 = CALL @foo, %0:i32, implicit-def dead $arguments, implicit $sp32, implicit $sp64
+    STORE8_I32_A32 0, 0, %0:i32, %1:i32, implicit-def dead $arguments
+    RETURN %0:i32, implicit-def dead $arguments
+
+  bb.2:
+  ; predecessors: %bb.0
+    %2:i32 = CONST_I32 0, implicit-def dead $arguments
+    RETURN %2:i32, implicit-def dead $arguments