[llvm-commits] [llvm] r46393 - in /llvm/trunk: lib/Transforms/Utils/InlineFunction.cpp test/CFrontend/2008-01-26-ReadOnlyByVal.c

[Duncan Sands]

Author: baldrick
Date: Sat Jan 26 00:41:49 2008
New Revision: 46393

URL: http://llvm.org/viewvc/llvm-project?rev=46393&view=rev
Log:
Create an explicit copy for byval parameters even
when inlining a readonly function.

Added:
    llvm/trunk/test/CFrontend/2008-01-26-ReadOnlyByVal.c
Modified:
    llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp

Modified: llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp?rev=46393&r1=46392&r2=46393&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp Sat Jan 26 00:41:49 2008
@@ -240,12 +240,15 @@
          E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
       Value *ActualArg = *AI;
       
-      // 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 (CalledFunc->paramHasAttr(ArgNo+1, ParamAttr::ByVal) &&
-          !CalledFunc->onlyReadsMemory()) {
+      // When byval arguments are inlined, we need to make the copy implied
+      // by them explicit.  It is tempting to think that this is not needed if
+      // the callee is readonly, because the callee doesn't modify the struct.
+      // However this would be wrong: readonly means that any writes the callee
+      // performs are not visible to the caller.  But writes by the callee to
+      // an argument passed byval are by definition not visible to the caller!
+      // Since we allow this kind of readonly function, there needs to be an
+      // explicit copy in order to keep the writes invisible after inlining.
+      if (CalledFunc->paramHasAttr(ArgNo+1, ParamAttr::ByVal)) {
         const Type *AggTy = cast<PointerType>(I->getType())->getElementType();
         const Type *VoidPtrTy = PointerType::getUnqual(Type::Int8Ty);
         

Added: llvm/trunk/test/CFrontend/2008-01-26-ReadOnlyByVal.c
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CFrontend/2008-01-26-ReadOnlyByVal.c?rev=46393&view=auto

==============================================================================
--- llvm/trunk/test/CFrontend/2008-01-26-ReadOnlyByVal.c (added)
+++ llvm/trunk/test/CFrontend/2008-01-26-ReadOnlyByVal.c Sat Jan 26 00:41:49 2008
@@ -0,0 +1,19 @@
+// RUN: %llvmgcc %s -S -O1 -o - | llvm-as | opt -std-compile-opts | llvm-dis | not grep add
+
+struct S { int A; int B; int C; int D; };
+
+int f(struct S x) __attribute__ ((const));
+
+static int __attribute__ ((const)) g(struct S x) {
+	x.A = x.B;
+	return f(x);
+}
+
+int h(void) {
+	struct S x;
+	int r;
+	x.A = 0;
+	x.B = 9;
+	r = g(x);
+	return r + x.A;
+}