[PATCH] D28504: [WebAssembly] Only set one use at a time in FixFunctionBitcasts

[Derek Schuff via Phabricator via llvm-commits]

dschuff updated this revision to Diff 83855.
dschuff added a comment.

Use RAUW for constants, but only add a single use to the worklist


https://reviews.llvm.org/D28504

Files:
  lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp
  test/CodeGen/WebAssembly/function-bitcasts.ll


Index: test/CodeGen/WebAssembly/function-bitcasts.ll
===================================================================
--- test/CodeGen/WebAssembly/function-bitcasts.ll
+++ test/CodeGen/WebAssembly/function-bitcasts.ll
@@ -7,11 +7,18 @@
 
 ; CHECK-LABEL: test:
 ; CHECK-NEXT: call        .Lbitcast at FUNCTION{{$}}
+; CHECK-NEXT: call        .Lbitcast at FUNCTION{{$}}
 ; CHECK-NEXT: call        .Lbitcast.1 at FUNCTION{{$}}
 ; CHECK-NEXT: i32.const   $push[[L0:[0-9]+]]=, 0
 ; CHECK-NEXT: call        .Lbitcast.2 at FUNCTION, $pop[[L0]]{{$}}
+; CHECK-NEXT: i32.const   $push[[L1:[0-9]+]]=, 0
+; CHECK-NEXT: call        .Lbitcast.2 at FUNCTION, $pop[[L1]]{{$}}
+; CHECK-NEXT: i32.const   $push[[L2:[0-9]+]]=, 0
+; CHECK-NEXT: call        .Lbitcast.2 at FUNCTION, $pop[[L2]]{{$}}
+; CHECK-NEXT: call        foo0 at FUNCTION
 ; CHECK-NEXT: i32.call    $drop=, .Lbitcast.3 at FUNCTION{{$}}
 ; CHECK-NEXT: call        foo2 at FUNCTION{{$}}
+; CHECK-NEXT: call        foo1 at FUNCTION{{$}}
 ; CHECK-NEXT: call        foo3 at FUNCTION{{$}}
 ; CHECK-NEXT: .endfunc
 
@@ -47,10 +54,19 @@
 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
 }
Index: lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp
===================================================================
--- lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp
+++ lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp
@@ -62,12 +62,20 @@
 // 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 +130,11 @@
 
 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);
+    FindUses(&F, F, Uses, ConstantBCs);
 
   DenseMap<std::pair<Function *, FunctionType *>, Function *> Wrappers;
 
@@ -153,6 +162,7 @@
       U->get()->replaceAllUsesWith(Wrapper);
     else
       U->set(Wrapper);
+
   }
 
   return true;


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