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Hi Bastien, Weird gcc is generating fma for my platform STEricsson Novathor with Linaro, code works. It also works when I use LLVM to generate fma (using llc -mtriple=armv7-eabi). Maybe someone from ARM can answer the question ? Seb From: JF Bastien [mailto:jfb at google.com] Sent: Friday, November 09, 2012 5:36 PM To: Sebastien DELDON-GNB Cc: Anitha Boyapati; llvmdev at...

...ay, November 09, 2012 6:27 PM > To: Sebastien DELDON-GNB > Cc: JF Bastien; llvmdev at cs.uiuc.edu > Subject: Re: [LLVMdev] fmac generation for cortex-a9 > > Hi Sebastien, > > ARMv7-M has VFMA and LLVM's "triple" is far from perfect. > > Wikipedia tells me NovaThor can also be A15, or STE could have cramped a > VFPv4 in it? ;) Or possibly, your code never branches into the VFMA. > Many things could be happening, but usually, VFMA shouldn't be generated > for A9. > > A GCC bug, maybe? > > > On 9 November 2012 16:51, Sebastien DEL...

Hi Sebastien, ARMv7-M has VFMA and LLVM's "triple" is far from perfect. Wikipedia tells me NovaThor can also be A15, or STE could have cramped a VFPv4 in it? ;) Or possibly, your code never branches into the VFMA. Many things could be happening, but usually, VFMA shouldn't be generated for A9. A GCC bug, maybe? On 9 November 2012 16:51, Sebastien DELDON-GNB <sebastien.deldon at st.com&g...

...: Sebastien DELDON-GNB > > Cc: JF Bastien; llvmdev at cs.uiuc.edu > > Subject: Re: [LLVMdev] fmac generation for cortex-a9 > > > > Hi Sebastien, > > > > ARMv7-M has VFMA and LLVM's "triple" is far from perfect. > > > > Wikipedia tells me NovaThor can also be A15, or STE could have cramped a > > VFPv4 in it? ;) Or possibly, your code never branches into the VFMA. > > Many things could be happening, but usually, VFMA shouldn't be generated > > for A9. > > > > A GCC bug, maybe? > > > > > > On...

...To: Sebastien DELDON-GNB > Cc: JF Bastien; llvmdev at cs.uiuc.edu<mailto:llvmdev at cs.uiuc.edu> > Subject: Re: [LLVMdev] fmac generation for cortex-a9 > > Hi Sebastien, > > ARMv7-M has VFMA and LLVM's "triple" is far from perfect. > > Wikipedia tells me NovaThor can also be A15, or STE could have cramped a > VFPv4 in it? ;) Or possibly, your code never branches into the VFMA. > Many things could be happening, but usually, VFMA shouldn't be generated > for A9. > > A GCC bug, maybe? > > > On 9 November 2012 16:51, Sebastien DELDON...

AFAIK A9 doesn't have VFPv4 or AdvSIMDv2, so it doesn't have VFMA. I don't know what LLVM does, but it shouldn't emit VFMA when you target A9. VMLA isn't a fused multiply-add, it's a multiply followed by an add and has different latency as well as precision. On Thu, Nov 8, 2012 at 4:57 AM, Sebastien DELDON-GNB < sebastien.deldon at st.com> wrote: > Hi Anitha,

Hi Anitha, Thanks for your answer but -mcpu=cortex-a9 -mattr=+vfp4 doesn' t enable fused mac generation for me. I would like just to understand why -mtriple=armv7-eabi enables it while -mcpu=cortex-a9 seems to disable it ? Seb > -----Original Message----- > From: Anitha Boyapati [mailto:anitha.boyapati at gmail.com] > Sent: Thursday, November 08, 2012 10:22 AM > To: Sebastien