Dead Code Elimination. I’m going to try re-working it following some of the
insights Don Quixote provided.
From: Cameron Zwarich [mailto:zwarich at apple.com]
Sent: Monday, November 21, 2011 12:17 PM
To: Michael Smith
Cc: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] Optimization of array access
Where does the -time-passes option say the time is going?
Sent from my iPhone
On Nov 21, 2011, at 8:58 AM, Michael Smith <Michael.Smith at
synopsys.com<mailto:Michael.Smith at synopsys.com>> wrote:
I’ve attached a 2 examples of patterns for updating an array. They’re simplified
examples of some code generation I’m doing where I need to pass a large, unknown
number of arguments (ints, doubles, pointers to other information) to a
function.
The two patterns are:
Stack[0] = 0;
Stack[1] = 1;
Stack[2] = 42;
And
Int I = 0;
Stack[i++] = 0;
Stack[i++] = 1;
Stack[i++] = 42;
I’ve found that the optimizer is much faster at handling the 2nd pattern than
the 1st. With 3000 assignments - as in the examples attached – “opt
–std-compile-opts –S func1.ll –o func1.opt” takes 10 seconds, while func2.ll
takes 0.2s. Anyone have any ideas why?
I’ve tested with LLVM 2.9, and LLVM 3.0 RC1.
Regards,
Michael
<opt.zip>
_______________________________________________
LLVM Developers mailing list
LLVMdev at cs.uiuc.edu<mailto:LLVMdev at cs.uiuc.edu>
http://llvm.cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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Sorry, Dead Store Elimination.
From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Michael Smith
Sent: Monday, November 21, 2011 12:20 PM
To: Cameron Zwarich
Cc: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] Optimization of array access
Dead Code Elimination. I’m going to try re-working it following some of the
insights Don Quixote provided.
From: Cameron Zwarich [mailto:zwarich at apple.com]
Sent: Monday, November 21, 2011 12:17 PM
To: Michael Smith
Cc: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] Optimization of array access
Where does the -time-passes option say the time is going?
Sent from my iPhone
On Nov 21, 2011, at 8:58 AM, Michael Smith <Michael.Smith at
synopsys.com<mailto:Michael.Smith at synopsys.com>> wrote:
I’ve attached a 2 examples of patterns for updating an array. They’re simplified
examples of some code generation I’m doing where I need to pass a large, unknown
number of arguments (ints, doubles, pointers to other information) to a
function.
The two patterns are:
Stack[0] = 0;
Stack[1] = 1;
Stack[2] = 42;
And
Int I = 0;
Stack[i++] = 0;
Stack[i++] = 1;
Stack[i++] = 42;
I’ve found that the optimizer is much faster at handling the 2nd pattern than
the 1st. With 3000 assignments - as in the examples attached – “opt
–std-compile-opts –S func1.ll –o func1.opt” takes 10 seconds, while func2.ll
takes 0.2s. Anyone have any ideas why?
I’ve tested with LLVM 2.9, and LLVM 3.0 RC1.
Regards,
Michael
<opt.zip>
_______________________________________________
LLVM Developers mailing list
LLVMdev at cs.uiuc.edu<mailto:LLVMdev at cs.uiuc.edu>
http://llvm.cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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On Mon, Nov 21, 2011 at 1:03 PM, Michael Smith <Michael.Smith at synopsys.com> wrote:> Sorry, Dead Store Elimination.Hmm... does tweaking the value of BlockScanLimit in MemoryDependenceAnalysis.cpp help? -Eli> > > > From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On > Behalf Of Michael Smith > Sent: Monday, November 21, 2011 12:20 PM > To: Cameron Zwarich > > Cc: llvmdev at cs.uiuc.edu > Subject: Re: [LLVMdev] Optimization of array access > > > > Dead Code Elimination. I’m going to try re-working it following some of the > insights Don Quixote provided. > > > > From: Cameron Zwarich [mailto:zwarich at apple.com] > Sent: Monday, November 21, 2011 12:17 PM > To: Michael Smith > Cc: llvmdev at cs.uiuc.edu > Subject: Re: [LLVMdev] Optimization of array access > > > > Where does the -time-passes option say the time is going? > > Sent from my iPhone > > On Nov 21, 2011, at 8:58 AM, Michael Smith <Michael.Smith at synopsys.com> > wrote: > > I’ve attached a 2 examples of patterns for updating an array. They’re > simplified examples of some code generation I’m doing where I need to pass a > large, unknown number of arguments (ints, doubles, pointers to other > information) to a function. > > > > The two patterns are: > > Stack[0] = 0; > > Stack[1] = 1; > > Stack[2] = 42; > > And > > Int I = 0; > > Stack[i++] = 0; > > Stack[i++] = 1; > > Stack[i++] = 42; > > > > I’ve found that the optimizer is much faster at handling the 2nd pattern > than the 1st. With 3000 assignments - as in the examples attached – “opt > –std-compile-opts –S func1.ll –o func1.opt” takes 10 seconds, while func2.ll > takes 0.2s. Anyone have any ideas why? > > > > I’ve tested with LLVM 2.9, and LLVM 3.0 RC1. > > > > Regards, > > Michael > > <opt.zip> > > _______________________________________________ > LLVM Developers mailing list > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > _______________________________________________ > LLVM Developers mailing list > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > >