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58e9ee85fd
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Teach SimplifyCFG about magic pointer constants.
Weird code sometimes uses pointer constants other than null. This patch
teaches SimplifyCFG to build switch instructions in those cases.
Code like this:
void f(const char *x) {
if (!x)
puts("null");
else if ((uintptr_t)x == 1)
puts("one");
else if (x == (char*)2 || x == (char*)3)
puts("two");
else if ((intptr_t)x == 4)
puts("four");
else
puts(x);
}
Now becomes a switch:
define void @f(i8* %x) nounwind ssp {
entry:
%magicptr23 = ptrtoint i8* %x to i64 ; <i64> [#uses=1]
switch i64 %magicptr23, label %if.else16 [
i64 0, label %if.then
i64 1, label %if.then2
i64 2, label %if.then9
i64 3, label %if.then9
i64 4, label %if.then14
]
Note that LLVM's own DenseMap uses magic pointers.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95439 91177308-0d34-0410-b5e6-96231b3b80d8
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2010-02-05 22:03:18 +00:00 |
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