[WebAssembly] Support opaque pointers in AddMissingPrototypes

[nikic]

Summary

The change here is basically the same as in D108880: Rather than looking at bitcasts, look at calls and their function type. We still need to look through bitcasts to find those calls.

The change in llvm/test/CodeGen/WebAssembly/add-prototypes-conflict.ll is due to different visitation order. add-prototypes-opaque-ptrs.ll is a copy of add-prototypes.ll with -force-opaque-pointers.

[tlively]

LGTM

llvm/lib/Target/WebAssembly/WebAssemblyAddMissingPrototypes.cpp

119

This lint looks like a real fix.

llvm/lib/Target/WebAssembly/WebAssemblyAddMissingPrototypes.cpp

for (Function &F : M) {
     unsigned NumParams = F.getFunctionType()->getNumParams();
     if (NumParams != 0) {
       if (!(NumParams == 1 && F.arg_begin()->hasStructRetAttr()))
         report_fatal_error("Functions with 'no-prototype' attribute should "
                            "not have params: " +
                            F.getName());
     }
 
-    // Create a function prototype based on the first call site (first bitcast)
-    // that we find.
+    // Find calls of this function, looking through bitcasts.
+    SmallVector<CallBase *> Calls;
+    SmallVector<Value *> Worklist;
+    Worklist.push_back(&F);
+    while (!Worklist.empty()) {
+      Value *V = Worklist.pop_back_val();
+      for (User *U : V->users()) {
+        if (auto *BC = dyn_cast<BitCastOperator>(U))
+          Worklist.push_back(BC);
+        else if (auto *CB = dyn_cast<CallBase>(U))
+          if (CB->getCalledOperand() == V)
+            Calls.push_back(CB);
+      }
+    }
+
+    // Create a function prototype based on the first call site that we find.
     FunctionType *NewType = nullptr;
-    for (Use &U : F.uses()) {
-      LLVM_DEBUG(dbgs() << "prototype-less use: " << F.getName() << "\n");
-      LLVM_DEBUG(dbgs() << *U.getUser() << "\n");
-      if (auto *BC = dyn_cast<BitCastOperator>(U.getUser())) {
-        if (auto *DestType = dyn_cast<FunctionType>(
-                BC->getDestTy()->getPointerElementType())) {
-          if (!NewType) {
-            // Create a new function with the correct type
-            NewType = DestType;
-            LLVM_DEBUG(dbgs() << "found function type: " << *NewType << "\n");
-          } else if (NewType != DestType) {
-            errs() << "warning: prototype-less function used with "
-                      "conflicting signatures: "
-                   << F.getName() << "\n";
-            LLVM_DEBUG(dbgs() << "  " << *DestType << "\n");
-            LLVM_DEBUG(dbgs() << "  "<<  *NewType << "\n");
-          }
-        }
-      }
-    }
+    for (CallBase *CB : Calls) {
+      LLVM_DEBUG(dbgs() << "prototype-less call of " << F.getName() << ":\n");
+      LLVM_DEBUG(dbgs() << *CB << "\n");
+      FunctionType *DestType = CB->getFunctionType();
 
     if (!NewType) {
       LLVM_DEBUG(
           dbgs() << "could not derive a function prototype from usage: " +
                         F.getName() + "\n");
       // We could not derive a type for this function.  In this case strip
       // the isVarArg and make it a simple zero-arg function.  This has more
       // chance of being correct.  The current signature of (...) is illegal in

llvm/test/CodeGen/WebAssembly/add-prototypes-conflict.ll

 ; RUN: opt -S -wasm-add-missing-prototypes -o %t.ll %s 2>&1 | FileCheck %s -check-prefix=WARNING
 ; RUN: cat %t.ll | FileCheck %s
 
 target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32-unknown-unknown"
 
 ; WARNING: warning: prototype-less function used with conflicting signatures: foo
 
 ; CHECK-LABEL: @call_with_conflicting_prototypes
-; CHECK: %call1 = call i64 @foo(i32 42)
-; CHECK: %call2 = call i64 bitcast (i64 (i32)* @foo to i64 (i32, i32)*)(i32 42, i32 43)
+; CHECK: %call1 = call i64 bitcast (i64 (i32, i32)* @foo to i64 (i32)*)(i32 42)
+; CHECK: %call2 = call i64 @foo(i32 42, i32 43)
 define void @call_with_conflicting_prototypes() {
   %call1 = call i64 bitcast (i64 (...)* @foo to i64 (i32)*)(i32 42)
   %call2 = call i64 bitcast (i64 (...)* @foo to i64 (i32, i32)*)(i32 42, i32 43)
   ret void
 }
 
-; CHECK: declare extern_weak i64 @foo(i32)
+; CHECK: declare extern_weak i64 @foo(i32, i32)
 declare extern_weak i64 @foo(...) #1
 
 ; CHECK-NOT: attributes {{.*}} = { {{.*}}"no-prototype"{{.*}} }
 attributes #1 = { "no-prototype" }

llvm/test/CodeGen/WebAssembly/add-prototypes-opaque-ptrs.ll

+; RUN: opt -S -wasm-add-missing-prototypes -force-opaque-pointers %s | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+; CHECK: @foo_addr = global ptr @foo, align 8
+@foo_addr = global i64 (i32)* bitcast (i64 (...)* @foo to i64 (i32)*), align 8
+
+; CHECK: @foo_addr_i8 = global ptr @foo, align 8
+@foo_addr_i8 = global i8* bitcast (i64 (...)* @foo to i8*), align 8
+
+; CHECK-LABEL: @call_foo
+; CHECK: %call = call i64 @foo(i32 42)
+define void @call_foo(i32 %a) {
+  %call = call i64 bitcast (i64 (...)* @foo to i64 (i32)*)(i32 42)
+  ret void
+}
+
+; CHECK-LABEL: @call_foo_ptr
+; CHECK: %1 = bitcast ptr @foo to ptr
+; CHECK-NEXT: %call = call i64 %1(i32 43)
+define i64 @call_foo_ptr(i32 %a) {
+  %1 = bitcast i64 (...)* @foo to i64 (i32)*
+  %call = call i64 (i32) %1(i32 43)
+  ret i64 %call
+}
+
+; CHECK-LABEL: @to_intptr_inst
+; CHECK: %1 = bitcast ptr @foo to ptr
+; CHECK-NEXT: ret ptr %1
+define i8* @to_intptr_inst() {
+  %1 = bitcast i64 (...)* @foo to i8*
+  ret i8* %1
+}
+
+; CHECK-LABEL: @to_intptr_constexpr
+; CHECK: ret ptr @foo
+define i8* @to_intptr_constexpr() {
+  ret i8* bitcast (i64 (...)* @foo to i8*)
+}
+
+; CHECK-LABEL: @null_compare
+; CHECK: br i1 icmp eq (ptr @foo, ptr null), label %if.then, label %if.end
+define i8 @null_compare() {
+  br i1 icmp eq (i64 (...)* @foo, i64 (...)* null), label %if.then, label %if.end
+if.then:
+  ret i8 0
+if.end:
+  ret i8 1
+}
+
+; CHECK-LABEL: @as_paramater
+; CHECK: call void @func_param(ptr @foo)
+define void @as_paramater() {
+  call void @func_param(i64 (...)* @foo)
+  ret void
+}
+
+; Check if a sret parameter works in a no-prototype function.
+; CHECK-LABEL: @sret_param
+; CHECK: call void @make_struct_foo(ptr sret(%struct.foo) %foo)
+%struct.foo = type { i32, i32 }
+declare void @make_struct_foo(%struct.foo* sret(%struct.foo), ...) #1
+define void @sret_param() {
+  %foo = alloca %struct.foo, align 4
+  call void bitcast (void (%struct.foo*, ...)* @make_struct_foo to void (%struct.foo*)*)(%struct.foo* sret(%struct.foo) %foo)
+  ret void
+}
+
+declare void @func_param(i64 (...)*)
+
+; CHECK: declare void @func_not_called()
+declare void @func_not_called(...) #1
+
+; CHECK: declare extern_weak i64 @foo(i32)
+declare extern_weak i64 @foo(...) #1
+
+; CHECK-NOT: attributes {{.*}} = { {{.*}}"no-prototype"{{.*}} }
+attributes #1 = { "no-prototype" }