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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86847 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-11-11 17:51:27 +00:00
parent d682a60c4e
commit 6fdfc9c630
1 changed files with 28 additions and 0 deletions
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28
lib/Target/README.txt
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@ -1682,3 +1682,31 @@ entry:
}
//===---------------------------------------------------------------------===//
IPSCCP does not currently propagate argument dependent constants through
functions where it does not not all of the callers. This includes functions
with normal external linkage as well as templates, C99 inline functions etc.
Specifically, it does nothing to:
define i32 @test(i32 %x, i32 %y, i32 %z) nounwind {
entry:
%0 = add nsw i32 %y, %z
%1 = mul i32 %0, %x
%2 = mul i32 %y, %z
%3 = add nsw i32 %1, %2
ret i32 %3
}
define i32 @test2() nounwind {
entry:
%0 = call i32 @test(i32 1, i32 2, i32 4) nounwind
ret i32 %0
}
It would be interesting extend IPSCCP to be able to handle simple cases like
this, where all of the arguments to a call are constant. Because IPSCCP runs
before inlining, trivial templates and inline functions are not yet inlined.
The results for a function + set of constant arguments should be memoized in a
map.
//===---------------------------------------------------------------------===//