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Pure/const functions with ByVal parameters cannot 

be marked readonly either.

llvm-svn: 46456
This commit is contained in:
Duncan Sands 2008-01-28 19:25:47 +00:00
parent 99929d20e7
commit 2a80ba8c7c
1 changed files with 10 additions and 5 deletions
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15
llvm/test/CFrontend/2008-01-25-ByValReadNone.c
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@ -1,10 +1,15 @@
// RUN: %llvmgcc -O3 -S -o - -emit-llvm %s | grep readonly
// RUN: %llvmgcc -O3 -S -o - -emit-llvm %s | not grep readonly
// RUN: %llvmgcc -O3 -S -o - -emit-llvm %s | not grep readnone
// The struct being passed byval means that we need to mark the
// function readonly instead of readnone. Readnone would allow
// stores to the arg to be deleted in the caller.
// The struct being passed byval means that we cannot mark the
// function readnone. Readnone would allow stores to the arg to
// be deleted in the caller. We also don't allow readonly since
// the callee might write to the byval parameter. The inliner
// would have to assume the worse and introduce an explicit
// temporary when inlining such a function, which is costly for
// the common case in which the byval argument is not written.
struct S { int A[1000]; };
int __attribute__ ((const)) f(struct S x) { return x.A[0]; }
int g(struct S x) __attribute__ ((pure));
int h(struct S x) { return g(x); }