[LLVMdev] llvm useability?

Christophe Avoinne christophe.avoinne at laposte.net
Tue Jan 22 12:11:35 PST 2008

What about ARM target ? I mean iPhone/iPod Touch has an ARM11 with a FPE 
and a VFPE. Does llvm-gcc 2.2 generates better code for them ?

I'm a bit disappointed about the llvm-gcc 2.0 I tried for my iPod Touch 
as I saw it generated ARM code not very optimically : r7(apparently used 
like a frame pointer even when -fomit-frame-pointer is given) largely 
overused, generated code like "mov rx, imm8;orr rx, rx, imm8';add rx, 
rx, ry" instead of "add rx, ry, imm8;add rx, rx, imm8'", etc.

I'm also wondering if the official SDK expected for February offers a 
llvm-gcc as a c/c++ compiler. Which version ?


On 21/01/2008 22:55:30, Chris Lattner (sabre at nondot.org) wrote:
 > On Jan 21, 2008, at 4:09 AM, Neal Becker wrote:
 > > Has llvm reached the point that it is useable as a mainstream c++
 > > compiler?
 > Yes. LLVM 2.2 will be out in a few weeks, it will be the best release
 > yet. Many people use llvm to build large C++ code bases.
 > > Are there benchmarks available comparing generated code to gcc4? My
 > > primary interest is scientific-type computing.
 > There are lots of benchmarks (see the nightly tester for example), but
 > it always makes sense to pick your own benchmark and do an evaluation
 > yourself. If you know of any important and self-contained benchmarks
 > that can be added to our performance testsuite, please let us know.
 > The most important thing to know for numeric performance is that LLVM
 > currently generates very poor code when targeting machines that do not
 > have SSE2 or later. When building llvm-gcc, make sure to configure it
 > for a CPU that has SSE2 or later to get good performance.
 > -Chris
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