Inliner: Handle readonly attribute per argument when adding memcpy

Patch by: Vincent Lejeune

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193356 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Utils/InlineFunction.cpp

@@ -337,33 +337,35 @@ static void UpdateCallGraphAfterInlining(CallSite CS,
 
 /// HandleByValArgument - When inlining a call site that has a byval argument,
 /// we have to make the implicit memcpy explicit by adding it.
-static Value *HandleByValArgument(Value *Arg, Instruction *TheCall,
+static Value *HandleByValArgument(Value *PassedValue,
+                                  const Argument *ArgumentSignature,
+                                  Instruction *TheCall,
                                   const Function *CalledFunc,
                                   InlineFunctionInfo &IFI,
                                   unsigned ByValAlignment) {
-  Type *AggTy = cast<PointerType>(Arg->getType())->getElementType();
+  Type *AggTy = cast<PointerType>(PassedValue->getType())->getElementType();
 
   // If the called function is readonly, then it could not mutate the caller's
   // copy of the byval'd memory.  In this case, it is safe to elide the copy and
   // temporary.
-  if (CalledFunc->onlyReadsMemory()) {
+  if (CalledFunc->onlyReadsMemory() || ArgumentSignature->onlyReadsMemory()) {
     // If the byval argument has a specified alignment that is greater than the
     // passed in pointer, then we either have to round up the input pointer or
     // give up on this transformation.
     if (ByValAlignment <= 1)  // 0 = unspecified, 1 = no particular alignment.
-      return Arg;
+      return PassedValue;
 
     // If the pointer is already known to be sufficiently aligned, or if we can
     // round it up to a larger alignment, then we don't need a temporary.
-    if (getOrEnforceKnownAlignment(Arg, ByValAlignment,
+    if (getOrEnforceKnownAlignment(PassedValue, ByValAlignment,
                                    IFI.TD) >= ByValAlignment)
-      return Arg;
+      return PassedValue;
     
     // Otherwise, we have to make a memcpy to get a safe alignment.  This is bad
     // for code quality, but rarely happens and is required for correctness.
   }
   
-  LLVMContext &Context = Arg->getContext();
+  LLVMContext &Context = PassedValue->getContext();
 
   Type *VoidPtrTy = Type::getInt8PtrTy(Context);
   
@@ -379,7 +381,7 @@ static Value *HandleByValArgument(Value *Arg, Instruction *TheCall,
   
   Function *Caller = TheCall->getParent()->getParent(); 
   
-  Value *NewAlloca = new AllocaInst(AggTy, 0, Align, Arg->getName(), 
+  Value *NewAlloca = new AllocaInst(AggTy, 0, Align, PassedValue->getName(),
                                     &*Caller->begin()->begin());
   // Emit a memcpy.
   Type *Tys[3] = {VoidPtrTy, VoidPtrTy, Type::getInt64Ty(Context)};
@@ -387,7 +389,7 @@ static Value *HandleByValArgument(Value *Arg, Instruction *TheCall,
                                                  Intrinsic::memcpy, 
                                                  Tys);
   Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall);
-  Value *SrcCast = new BitCastInst(Arg, VoidPtrTy, "tmp", TheCall);
+  Value *SrcCast = new BitCastInst(PassedValue, VoidPtrTy, "tmp", TheCall);
   
   Value *Size;
   if (IFI.TD == 0)
@@ -588,13 +590,14 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
     for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
          E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
       Value *ActualArg = *AI;
+      const Argument *Arg = I;
 
       // When byval arguments actually inlined, we need to make the copy implied
       // by them explicit.  However, we don't do this if the callee is readonly
       // or readnone, because the copy would be unneeded: the callee doesn't
       // modify the struct.
       if (CS.isByValArgument(ArgNo)) {
-        ActualArg = HandleByValArgument(ActualArg, TheCall, CalledFunc, IFI,
+        ActualArg = HandleByValArgument(ActualArg, Arg, TheCall, CalledFunc, IFI,
                                         CalledFunc->getParamAlignment(ArgNo+1));
  
         // Calls that we inline may use the new alloca, so we need to clear

test/Transforms/Inline/byval.ll

@@ -25,7 +25,7 @@ entry:
 	store i64 2, i64* %tmp4, align 4
 	call void @f( %struct.ss* byval  %S ) nounwind 
 	ret i32 0
-; CHECK: @test1()
+; CHECK-LABEL: @test1()
 ; CHECK: %S1 = alloca %struct.ss
 ; CHECK: %S = alloca %struct.ss
 ; CHECK: call void @llvm.memcpy
@@ -52,7 +52,7 @@ entry:
 	store i64 2, i64* %tmp4, align 4
 	%X = call i32 @f2( %struct.ss* byval  %S ) nounwind 
 	ret i32 %X
-; CHECK: @test2()
+; CHECK-LABEL: @test2()
 ; CHECK: %S = alloca %struct.ss
 ; CHECK-NOT: call void @llvm.memcpy
 ; CHECK: ret i32
@@ -74,7 +74,7 @@ entry:
 	%S = alloca %struct.ss, align 1  ;; May not be aligned.
 	call void @f3( %struct.ss* byval align 64 %S) nounwind 
 	ret void
-; CHECK: @test3()
+; CHECK-LABEL: @test3()
 ; CHECK: %S1 = alloca %struct.ss, align 64
 ; CHECK: %S = alloca %struct.ss
 ; CHECK: call void @llvm.memcpy
@@ -97,10 +97,35 @@ entry:
 	%S = alloca %struct.ss, align 2		; <%struct.ss*> [#uses=4]
 	%X = call i32 @f4( %struct.ss* byval align 64 %S ) nounwind 
 	ret i32 %X
-; CHECK: @test4()
+; CHECK-LABEL: @test4()
 ; CHECK: %S = alloca %struct.ss, align 64
 ; CHECK-NOT: call void @llvm.memcpy
 ; CHECK: call void @g3
 ; CHECK: ret i32 4
 }
 
+; Inlining a byval struct should NOT cause an explicit copy
+; into an alloca if the parameter is readonly
+
+define internal i32 @f5(%struct.ss* byval readonly %b) nounwind {
+entry:
+	%tmp = getelementptr %struct.ss* %b, i32 0, i32 0		; <i32*> [#uses=2]
+	%tmp1 = load i32* %tmp, align 4		; <i32> [#uses=1]
+	%tmp2 = add i32 %tmp1, 1		; <i32> [#uses=1]
+	ret i32 %tmp2
+}
+
+define i32 @test5() nounwind  {
+entry:
+	%S = alloca %struct.ss		; <%struct.ss*> [#uses=4]
+	%tmp1 = getelementptr %struct.ss* %S, i32 0, i32 0		; <i32*> [#uses=1]
+	store i32 1, i32* %tmp1, align 8
+	%tmp4 = getelementptr %struct.ss* %S, i32 0, i32 1		; <i64*> [#uses=1]
+	store i64 2, i64* %tmp4, align 4
+	%X = call i32 @f5( %struct.ss* byval  %S ) nounwind
+	ret i32 %X
+; CHECK-LABEL: @test5()
+; CHECK: %S = alloca %struct.ss
+; CHECK-NOT: call void @llvm.memcpy
+; CHECK: ret i32
+}