[llvm] r219501 - [PowerPC] Add feature for Power8 vector extensions

[Hal Finkel]

----- Original Message -----
> From: "Bill Schmidt" <wschmidt at linux.vnet.ibm.com>
> To: llvm-commits at cs.uiuc.edu
> Sent: Friday, October 10, 2014 10:09:29 AM
> Subject: [llvm] r219501 - [PowerPC] Add feature for Power8 vector extensions
> 
> Author: wschmidt
> Date: Fri Oct 10 10:09:28 2014
> New Revision: 219501
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=219501&view=rev
> Log:
> [PowerPC] Add feature for Power8 vector extensions
> 
> The current VSX feature for PowerPC specifies availability of the VSX
> instructions added with the 2.06 architecture version.  With 2.07,
> the
> architecture adds new instructions to both the Category:Vector and
> Category:VSX instruction sets.  Additionally, unaligned vector
> storage
> operations have improved performance.
> 
> This patch adds a feature to provide access to the new instructions
> and performance capabilities of Power8.  For compatibility with GCC,
> the feature is controlled via a new -mpower8-vector switch, and the
> feature causes the __POWER8_VECTOR__ builtin define to be generated
> by
> the preprocessor.
> 
> There is a companion patch for cfe being committed at the same time.
> 
> Modified:
>     llvm/trunk/lib/Target/PowerPC/PPC.td
>     llvm/trunk/lib/Target/PowerPC/PPCSubtarget.cpp
>     llvm/trunk/lib/Target/PowerPC/PPCSubtarget.h
> 
> Modified: llvm/trunk/lib/Target/PowerPC/PPC.td
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/PPC.td?rev=219501&r1=219500&r2=219501&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Target/PowerPC/PPC.td (original)
> +++ llvm/trunk/lib/Target/PowerPC/PPC.td Fri Oct 10 10:09:28 2014
> @@ -104,6 +104,10 @@ def FeatureQPX       : SubtargetFeature<
>  def FeatureVSX       : SubtargetFeature<"vsx","HasVSX", "true",
>                                          "Enable VSX instructions",
>                                          [FeatureAltivec]>;
> +def FeaturePower8Vector : SubtargetFeature<"power8-vector",
> "HasPower8Vector",

For all these backend things, I prefer less typing when doing so does not reduce clarity... can we please abbreviate this as FeatureP8Vector instead of spelling-out 'Power'. Furthermore, I find calling it 'vector' somewhat misleading because it refers to more than just vector instructions, but the P8 extensions to VSX generally. So I think that FeatureP8VSX is a better name. Same for all of the other variables, etc.

> +                                           "true",
> +                                           "Enable Power8 vector
> instructions",

It looks like IBM's preferred spelling is POWER8, and I'd like to keep a consistent spelling across the code base, and thus far, we've been using all caps for the others.

Thanks again,
Hal

> +                                           [FeatureVSX,
> FeatureAltivec]>;
>  
>  def DeprecatedMFTB   : SubtargetFeature<"", "DeprecatedMFTB",
>  "true",
>                                          "Treat mftb as deprecated">;
> @@ -116,7 +120,6 @@ def DeprecatedDST    : SubtargetFeature<
>  // CMPB         p6, p6x, p7        cmpb
>  // DFP          p6, p6x, p7        decimal floating-point
>  instructions
>  // POPCNTB      p5 through p7      popcntb and related instructions
> -// VSX          p7                 vector-scalar instruction set
>  
>  //===----------------------------------------------------------------------===//
>  // ABI Selection
>                                                               //
> 
> Modified: llvm/trunk/lib/Target/PowerPC/PPCSubtarget.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/PPCSubtarget.cpp?rev=219501&r1=219500&r2=219501&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Target/PowerPC/PPCSubtarget.cpp (original)
> +++ llvm/trunk/lib/Target/PowerPC/PPCSubtarget.cpp Fri Oct 10
> 10:09:28 2014
> @@ -94,6 +94,7 @@ void PPCSubtarget::initializeEnvironment
>    HasSPE = false;
>    HasQPX = false;
>    HasVSX = false;
> +  HasPower8Vector = false;
>    HasFCPSGN = false;
>    HasFSQRT = false;
>    HasFRE = false;
> @@ -155,8 +156,10 @@ void PPCSubtarget::initSubtargetFeatures
>  
>    // FIXME: For now, we disable VSX in little-endian mode until
>    endian
>    // issues in those instructions can be addressed.
> -  if (IsLittleEndian)
> +  if (IsLittleEndian) {
>      HasVSX = false;
> +    HasPower8Vector = false;
> +  }
>  
>    // Determine default ABI.
>    if (TargetABI == PPC_ABI_UNKNOWN) {
> 
> Modified: llvm/trunk/lib/Target/PowerPC/PPCSubtarget.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/PPCSubtarget.h?rev=219501&r1=219500&r2=219501&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Target/PowerPC/PPCSubtarget.h (original)
> +++ llvm/trunk/lib/Target/PowerPC/PPCSubtarget.h Fri Oct 10 10:09:28
> 2014
> @@ -91,6 +91,7 @@ protected:
>    bool HasSPE;
>    bool HasQPX;
>    bool HasVSX;
> +  bool HasPower8Vector;
>    bool HasFCPSGN;
>    bool HasFSQRT;
>    bool HasFRE, HasFRES, HasFRSQRTE, HasFRSQRTES;
> @@ -215,6 +216,7 @@ public:
>    bool hasSPE() const { return HasSPE; }
>    bool hasQPX() const { return HasQPX; }
>    bool hasVSX() const { return HasVSX; }
> +  bool hasPower8Vector() const { return HasPower8Vector; }
>    bool hasMFOCRF() const { return HasMFOCRF; }
>    bool hasISEL() const { return HasISEL; }
>    bool hasPOPCNTD() const { return HasPOPCNTD; }
> 
> 
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory