[Mesa-dev] [PATCH v3 2/2] R600/SI: Optimize SI_KILL for constant operands

[Tom Stellard]

On Wed, Feb 26, 2014 at 01:48:39PM +0900, Michel Dänzer wrote:
> From: Michel Dänzer <michel.daenzer at amd.com>
> 
> If the SI_KILL operand is constant, we can either clear the exec mask if
> the operand is negative, or do nothing otherwise.
> 
> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>

Reviewed-by: Tom Stellard <thomas.stellard at amd.com>

> ---
> 
> v3:
> * Use VSrc_32 for the SI_KILL operand.
> * Drop unused Depth parameter from SILowerControlFlowPass::Kill().
> * Use local variable 'Op' also in else path.
> 
>  lib/Target/R600/SIInstructions.td      |  4 ++--
>  lib/Target/R600/SILowerControlFlow.cpp | 19 +++++++++++++++----
>  test/CodeGen/R600/llvm.AMDGPU.kill.ll  | 10 +++++++---
>  3 files changed, 24 insertions(+), 9 deletions(-)
> 
> diff --git a/lib/Target/R600/SIInstructions.td b/lib/Target/R600/SIInstructions.td
> index b45da5c..7860987 100644
> --- a/lib/Target/R600/SIInstructions.td
> +++ b/lib/Target/R600/SIInstructions.td
> @@ -1333,7 +1333,7 @@ def SI_END_CF : InstSI <
>  
>  def SI_KILL : InstSI <
>    (outs),
> -  (ins VReg_32:$src),
> +  (ins VSrc_32:$src),
>    "SI_KILL $src",
>    [(int_AMDGPU_kill f32:$src)]
>  >;
> @@ -1425,7 +1425,7 @@ def : Pat<
>  
>  def : Pat <
>    (int_AMDGPU_kilp),
> -  (SI_KILL (V_MOV_B32_e32 0xbf800000))
> +  (SI_KILL 0xbf800000)
>  >;
>  
>  /* int_SI_vs_load_input */
> diff --git a/lib/Target/R600/SILowerControlFlow.cpp b/lib/Target/R600/SILowerControlFlow.cpp
> index fa5ee16..50dcf4e 100644
> --- a/lib/Target/R600/SILowerControlFlow.cpp
> +++ b/lib/Target/R600/SILowerControlFlow.cpp
> @@ -55,6 +55,7 @@
>  #include "llvm/CodeGen/MachineFunctionPass.h"
>  #include "llvm/CodeGen/MachineInstrBuilder.h"
>  #include "llvm/CodeGen/MachineRegisterInfo.h"
> +#include "llvm/IR/Constants.h"
>  
>  using namespace llvm;
>  
> @@ -294,6 +295,7 @@ void SILowerControlFlowPass::Branch(MachineInstr &MI) {
>  void SILowerControlFlowPass::Kill(MachineInstr &MI) {
>    MachineBasicBlock &MBB = *MI.getParent();
>    DebugLoc DL = MI.getDebugLoc();
> +  const MachineOperand &Op = MI.getOperand(0);
>  
>    // Kill is only allowed in pixel / geometry shaders
>    assert(MBB.getParent()->getInfo<SIMachineFunctionInfo>()->ShaderType ==
> @@ -301,10 +303,19 @@ void SILowerControlFlowPass::Kill(MachineInstr &MI) {
>           MBB.getParent()->getInfo<SIMachineFunctionInfo>()->ShaderType ==
>           ShaderType::GEOMETRY);
>  
> -  // Clear this pixel from the exec mask if the operand is negative
> -  BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_CMPX_LE_F32_e32), AMDGPU::VCC)
> -          .addImm(0)
> -          .addOperand(MI.getOperand(0));
> +  // Clear this thread from the exec mask if the operand is negative
> +  if ((Op.isImm() || Op.isFPImm())) {
> +    // Constant operand: Set exec mask to 0 or do nothing
> +    if (Op.isImm() ? (Op.getImm() & 0x80000000) :
> +        Op.getFPImm()->isNegative()) {
> +      BuildMI(MBB, &MI, DL, TII->get(AMDGPU::S_MOV_B64), AMDGPU::EXEC)
> +              .addImm(0);
> +    }
> +  } else {
> +    BuildMI(MBB, &MI, DL, TII->get(AMDGPU::V_CMPX_LE_F32_e32), AMDGPU::VCC)
> +           .addImm(0)
> +           .addOperand(Op);
> +  }
>  
>    MI.eraseFromParent();
>  }
> diff --git a/test/CodeGen/R600/llvm.AMDGPU.kill.ll b/test/CodeGen/R600/llvm.AMDGPU.kill.ll
> index bec5cdf..4ab6a8a 100644
> --- a/test/CodeGen/R600/llvm.AMDGPU.kill.ll
> +++ b/test/CodeGen/R600/llvm.AMDGPU.kill.ll
> @@ -1,13 +1,17 @@
>  ; RUN: llc < %s -march=r600 -mcpu=verde -verify-machineinstrs | FileCheck --check-prefix=SI %s
>  
> -; SI-LABEL: @kill_gs
> -; SI: V_CMPX_LE_F32
> +; SI-LABEL: @kill_gs_const
> +; SI-NOT: V_CMPX_LE_F32
> +; SI: S_MOV_B64 exec, 0
>  
> -define void @kill_gs() #0 {
> +define void @kill_gs_const() #0 {
>  main_body:
>    %0 = icmp ule i32 0, 3
>    %1 = select i1 %0, float 1.000000e+00, float -1.000000e+00
>    call void @llvm.AMDGPU.kill(float %1)
> +  %2 = icmp ule i32 3, 0
> +  %3 = select i1 %2, float 1.000000e+00, float -1.000000e+00
> +  call void @llvm.AMDGPU.kill(float %3)
>    ret void
>  }
>  
> -- 
> 1.9.0
> 
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/mesa-dev