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llvm-6502/include/llvm/Transforms
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Jakob Stoklund Olesen 58e9ee85fd 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
2010-02-05 22:03:18 +00:00
..
IPO Move per-function inline threshold calculation to a method. 2010-01-20 17:51:28 +00:00
Utils Teach SimplifyCFG about magic pointer constants. 2010-02-05 22:03:18 +00:00
Instrumentation.h remove the random sampling framework, which is not maintained anymore. 2010-01-02 20:07:03 +00:00
IPO.h Auto-upgrade free instructions to calls to the builtin free function. 2009-10-24 04:23:03 +00:00
RSProfiling.h Make a few more LLVM headers parsable as standalone headers. 2009-11-05 23:01:30 +00:00
Scalar.h Add an option for running GVN with redundant load processing disabled. 2009-11-14 02:27:51 +00:00