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Add some IRgen improvement notes. 

llvm-svn: 65146
This commit is contained in:
Daniel Dunbar 2009-02-20 19:34:45 +00:00
parent 27032de34b
commit 2f3a3d9f7a
1 changed files with 17 additions and 0 deletions
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17
clang/lib/CodeGen/README.txt
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@ -30,3 +30,20 @@ block.
//===---------------------------------------------------------------------===//
We should try and avoid generating basic blocks which only contain
jumps. At -O0, this penalizes us all the way from IRgen (malloc &
instruction overhead), all the way down through code generation and
assembly time.
On 176.gcc:expr.ll, it looks like over 12% of basic blocks are just
direct branches.
//===---------------------------------------------------------------------===//
There are some more places where we could avoid generating unreachable code. For
example:
void f0(int a) { abort(); if (a) printf("hi"); }
still generates a call to printf. This doesn't occur much in real
code, but would still be nice to clean up.
//===---------------------------------------------------------------------===//