llvm dev - May 2016 - status of IPO/IPCP?

The pass is pretty rudimental (as the comment at the top of the file
hints), and it seems LLVM already has IPSCCP (which should do a better
job at interprocedural constant propagation).
I'm also not entirely sure it's used anywhere.
Is there any reason to keep it around?

Thanks,

-- 
Davide

"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare

No tests fail with the patch below, so I would say it's pretty useless. It
seems that the C bindings are the only user but we can probably just have
them return IPSCCP instead.

Any idea why this wasn't removed when IPSCCP was introduced? Probably worth
understanding that before ripping it out, but in the current state of
things I don't think removing it will be problematic.

diff --git a/llvm/lib/Transforms/IPO/IPConstantPropagation.cpp
b/llvm/lib/Transforms/IPO/IPConstantPropagation.cpp
index a1533b3..24aea5c 100644
--- a/llvm/lib/Transforms/IPO/IPConstantPropagation.cpp
+++ b/llvm/lib/Transforms/IPO/IPConstantPropagation.cpp
@@ -51,7 +51,9 @@ char IPCP::ID = 0;
 INITIALIZE_PASS(IPCP, "ipconstprop",
                 "Interprocedural constant propagation", false, false)

-ModulePass *llvm::createIPConstantPropagationPass() { return new IPCP(); }
+ModulePass *llvm::createIPConstantPropagationPass() {
+  return createIPSCCPPass();
+}

 bool IPCP::runOnModule(Module &M) {
   if (skipModule(M))

-- Sean Silva


On Tue, May 3, 2016 at 3:06 PM, Davide Italiano via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> The pass is pretty rudimental (as the comment at the top of the file
> hints), and it seems LLVM already has IPSCCP (which should do a better
> job at interprocedural constant propagation).
> I'm also not entirely sure it's used anywhere.
> Is there any reason to keep it around?
>
> Thanks,
>
> --
> Davide
>
> "There are no solved problems; there are only problems that are more
> or less solved" -- Henri Poincare
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Sean Silva via llvm-dev <llvm-dev at lists.llvm.org>
writes:
> No tests fail with the patch below, so I would say it's pretty useless.
It
> seems that the C bindings are the only user but we can probably just have
them
> return IPSCCP instead.
I don't necessarily think your conclusion is wrong, but the patch isn't
proving what you think it's proving. In fact, the below passes all tests
as well. When you call passes through `opt` they don't end up calling
through the createXYZPass path.

diff --git a/lib/Transforms/IPO/IPConstantPropagation.cpp
b/lib/Transforms/IPO/IPConstantPropagation.cpp
index b3ee499..8d70b98 100644
--- a/lib/Transforms/IPO/IPConstantPropagation.cpp
+++ b/lib/Transforms/IPO/IPConstantPropagation.cpp
@@ -253,7 +253,9 @@ char IPCP::ID = 0;
 INITIALIZE_PASS(IPCP, "ipconstprop",
                 "Interprocedural constant propagation", false, false)
 
-ModulePass *llvm::createIPConstantPropagationPass() { return new IPCP(); }
+ModulePass *llvm::createIPConstantPropagationPass() {
+  llvm_unreachable("fnord");
+}
 
 bool IPCP::runOnModule(Module &M) {
   if (skipModule(M))
> Any idea why this wasn't removed when IPSCCP was introduced? Probably
worth
> understanding that before ripping it out, but in the current state of
things I
> don't think removing it will be problematic.
>
> diff --git a/llvm/lib/Transforms/IPO/IPConstantPropagation.cpp b/llvm/lib/
> Transforms/IPO/IPConstantPropagation.cpp
> index a1533b3..24aea5c 100644
> --- a/llvm/lib/Transforms/IPO/IPConstantPropagation.cpp
> +++ b/llvm/lib/Transforms/IPO/IPConstantPropagation.cpp
> @@ -51,7 +51,9 @@ char IPCP::ID = 0;
>  INITIALIZE_PASS(IPCP, "ipconstprop",
>                  "Interprocedural constant propagation", false,
false)
>  
> -ModulePass *llvm::createIPConstantPropagationPass() { return new IPCP(); }
> +ModulePass *llvm::createIPConstantPropagationPass() {
> +  return createIPSCCPPass();
> +}
>  
>  bool IPCP::runOnModule(Module &M) {
>    if (skipModule(M))
>
> -- Sean Silva
>
> On Tue, May 3, 2016 at 3:06 PM, Davide Italiano via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>     The pass is pretty rudimental (as the comment at the top of the file
>     hints), and it seems LLVM already has IPSCCP (which should do a better
>     job at interprocedural constant propagation).
>     I'm also not entirely sure it's used anywhere.
>     Is there any reason to keep it around?
>    
>     Thanks,
>    
>     --
>     Davide
>    
>     "There are no solved problems; there are only problems that are
more
>     or less solved" -- Henri Poincare
>     _______________________________________________
>     LLVM Developers mailing list
>     llvm-dev at lists.llvm.org
>     http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev