From aca5f1663aa5419799de4783cb453f974e92b3e3 Mon Sep 17 00:00:00 2001
From: Derek Schuff <dschuff@google.com>
Date: Tue, 10 Jan 2017 21:59:53 +0000
Subject: [PATCH] [WebAssembly] Only RAUW a constant once in
 FixFunctionBitcasts

When we collect 2 uses of a function in FindUses and then RAUW when we
visit the first, we end up visiting the wrapper (because the second was
RAUW'd).  We still want to use RAUW instead of just Use->set() because
it has special handling for Constants, so this patch just ensures that
only one use of each constant is added to the work list.

Differential Revision: https://reviews.llvm.org/D28504

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291603 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../WebAssemblyFixFunctionBitcasts.cpp          | 17 ++++++++++++-----
 test/CodeGen/WebAssembly/function-bitcasts.ll   | 16 ++++++++++++++++
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp b/lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp
index d5474a02ce0..adf904ee026 100644
--- a/lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp
+++ b/lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp
@@ -62,12 +62,19 @@ ModulePass *llvm::createWebAssemblyFixFunctionBitcasts() {
 // Recursively descend the def-use lists from V to find non-bitcast users of
 // bitcasts of V.
 static void FindUses(Value *V, Function &F,
-                     SmallVectorImpl<std::pair<Use *, Function *>> &Uses) {
+                     SmallVectorImpl<std::pair<Use *, Function *>> &Uses,
+                     SmallPtrSetImpl<Constant *> &ConstantBCs) {
   for (Use &U : V->uses()) {
     if (BitCastOperator *BC = dyn_cast<BitCastOperator>(U.getUser()))
-      FindUses(BC, F, Uses);
-    else if (U.get()->getType() != F.getType())
+      FindUses(BC, F, Uses, ConstantBCs);
+    else if (U.get()->getType() != F.getType()) {
+      if (isa<Constant>(U.get())) {
+        // Only add constant bitcasts to the list once; they get RAUW'd
+        auto c = ConstantBCs.insert(cast<Constant>(U.get()));
+        if (!c.second) continue;
+      }
       Uses.push_back(std::make_pair(&U, &F));
+    }
   }
 }
 
@@ -122,10 +129,10 @@ static Function *CreateWrapper(Function *F, FunctionType *Ty) {
 
 bool FixFunctionBitcasts::runOnModule(Module &M) {
   SmallVector<std::pair<Use *, Function *>, 0> Uses;
+  SmallPtrSet<Constant *, 2> ConstantBCs;
 
   // Collect all the places that need wrappers.
-  for (Function &F : M)
-    FindUses(&F, F, Uses);
+  for (Function &F : M) FindUses(&F, F, Uses, ConstantBCs);
 
   DenseMap<std::pair<Function *, FunctionType *>, Function *> Wrappers;
 
diff --git a/test/CodeGen/WebAssembly/function-bitcasts.ll b/test/CodeGen/WebAssembly/function-bitcasts.ll
index 49980da6eb8..e4f8f3fb6ca 100644
--- a/test/CodeGen/WebAssembly/function-bitcasts.ll
+++ b/test/CodeGen/WebAssembly/function-bitcasts.ll
@@ -7,11 +7,18 @@ target triple = "wasm32-unknown-unknown"
 
 ; CHECK-LABEL: test:
 ; CHECK-NEXT: call        .Lbitcast@FUNCTION{{$}}
+; CHECK-NEXT: call        .Lbitcast@FUNCTION{{$}}
 ; CHECK-NEXT: call        .Lbitcast.1@FUNCTION{{$}}
 ; CHECK-NEXT: i32.const   $push[[L0:[0-9]+]]=, 0
 ; CHECK-NEXT: call        .Lbitcast.2@FUNCTION, $pop[[L0]]{{$}}
+; CHECK-NEXT: i32.const   $push[[L1:[0-9]+]]=, 0
+; CHECK-NEXT: call        .Lbitcast.2@FUNCTION, $pop[[L1]]{{$}}
+; CHECK-NEXT: i32.const   $push[[L2:[0-9]+]]=, 0
+; CHECK-NEXT: call        .Lbitcast.2@FUNCTION, $pop[[L2]]{{$}}
+; CHECK-NEXT: call        foo0@FUNCTION
 ; CHECK-NEXT: i32.call    $drop=, .Lbitcast.3@FUNCTION{{$}}
 ; CHECK-NEXT: call        foo2@FUNCTION{{$}}
+; CHECK-NEXT: call        foo1@FUNCTION{{$}}
 ; CHECK-NEXT: call        foo3@FUNCTION{{$}}
 ; CHECK-NEXT: .endfunc
 
@@ -46,11 +53,20 @@ declare void @foo3()
 
 define void @test() {
 entry:
+  call void bitcast (void (i32)* @has_i32_arg to void ()*)()
   call void bitcast (void (i32)* @has_i32_arg to void ()*)()
   call void bitcast (i32 ()* @has_i32_ret to void ()*)()
   call void bitcast (void ()* @foo0 to void (i32)*)(i32 0)
+  %p = bitcast void ()* @foo0 to void (i32)*
+  call void %p(i32 0)
+  %q = bitcast void ()* @foo0 to void (i32)*
+  call void %q(i32 0)
+  %r = bitcast void (i32)* %q to void ()*
+  call void %r()
   %t = call i32 bitcast (void ()* @foo1 to i32 ()*)()
   call void bitcast (void ()* @foo2 to void ()*)()
+  call void @foo1()
   call void @foo3()
+
   ret void
 }
-- 
2.40.0