[llvm] Revert "[WebAssembly] Remove FAKE_USEs before ExplicitLocals" (PR #160553)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-webassembly

Author: Derek Schuff (dschuff)

<details>
<summary>Changes</summary>

Reverts llvm/llvm-project#<!-- -->160228
See https://github.com/llvm/llvm-project/pull/160228#issuecomment-3329752471

---
Full diff: https://github.com/llvm/llvm-project/pull/160553.diff


2 Files Affected:

- (modified) llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp (-14) 
- (removed) llvm/test/CodeGen/WebAssembly/fake-use.ll (-15) 


``````````diff
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
index 5c3127e2d3dc6..e6486e247209b 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
@@ -216,18 +216,6 @@ static MachineInstr *findStartOfTree(MachineOperand &MO,
   return Def;
 }
 
-// FAKE_USEs are no-ops, so remove them here so that the values used by them
-// will be correctly dropped later.
-static void removeFakeUses(MachineFunction &MF) {
-  SmallVector<MachineInstr *> ToDelete;
-  for (auto &MBB : MF)
-    for (auto &MI : MBB)
-      if (MI.isFakeUse())
-        ToDelete.push_back(&MI);
-  for (auto *MI : ToDelete)
-    MI->eraseFromParent();
-}
-
 bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
   LLVM_DEBUG(dbgs() << "********** Make Locals Explicit **********\n"
                        "********** Function: "
@@ -238,8 +226,6 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
   WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
   const auto *TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
 
-  removeFakeUses(MF);
-
   // Map non-stackified virtual registers to their local ids.
   DenseMap<unsigned, unsigned> Reg2Local;
 
diff --git a/llvm/test/CodeGen/WebAssembly/fake-use.ll b/llvm/test/CodeGen/WebAssembly/fake-use.ll
deleted file mode 100644
index d5732e628440a..0000000000000
--- a/llvm/test/CodeGen/WebAssembly/fake-use.ll
+++ /dev/null
@@ -1,15 +0,0 @@
-; RUN: llc < %s | llvm-mc -triple=wasm32-unknown-unknown
-
-target triple = "wasm32-unknown-unknown"
-
-define void @fake_use_test() {
-  %t = call i32 @foo()
-  tail call void (...) @llvm.fake.use(i32 %t)
-  ret void
-}
-
-declare void @foo()
-; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: readwrite)
-declare void @llvm.fake.use(...) #0
-
-attributes #0 = { mustprogress nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: readwrite) }

``````````

</details>


https://github.com/llvm/llvm-project/pull/160553