RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-11-23 11:13:28 +01:00
Code Issues Projects Releases Wiki Activity

R600: Implement getRsqrtEstimate

Browse Source 
Only do for f32 since I'm unclear on both what this is expecting
for the refinement steps in terms of accuracy, and what
f64 instruction actually provides.

llvm-svn: 225827
This commit is contained in:
Matt Arsenault 2015-01-13 20:53:18 +00:00
parent 66ec906910
commit 4cc5aca737
4 changed files with 63 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
lib/Target/R600/AMDGPUISelLowering.cpp
View File

@ -2567,6 +2567,24 @@ const char* AMDGPUTargetLowering::getTargetNodeName(unsigned Opcode) const {
}
}
SDValue AMDGPUTargetLowering::getRsqrtEstimate(SDValue Operand,
DAGCombinerInfo &DCI,
unsigned &RefinementSteps,
bool &UseOneConstNR) const {
SelectionDAG &DAG = DCI.DAG;
EVT VT = Operand.getValueType();
if (VT == MVT::f32) {
RefinementSteps = 0;
return DAG.getNode(AMDGPUISD::RSQ, SDLoc(Operand), VT, Operand);
}
// TODO: There is also f64 rsq instruction, but the documentation is less
// clear on its precision.
return SDValue();
}
static void computeKnownBitsForMinMax(const SDValue Op0,
const SDValue Op1,
APInt &KnownZero,

5
lib/Target/R600/AMDGPUISelLowering.h
View File

@ -167,6 +167,11 @@ public:
const char* getTargetNodeName(unsigned Opcode) const override;
SDValue getRsqrtEstimate(SDValue Operand,
DAGCombinerInfo &DCI,
unsigned &RefinementSteps,
bool &UseOneConstNR) const override;
virtual SDNode *PostISelFolding(MachineSDNode *N,
SelectionDAG &DAG) const {
return N;

5
test/CodeGen/R600/fsqrt.ll
View File

@ -1,4 +1,7 @@
; RUN: llc < %s -march=amdgcn -mcpu=tahiti -verify-machineinstrs | FileCheck %s
; RUN: llc -march=amdgcn -mcpu=tahiti -verify-machineinstrs < %s | FileCheck %s
; RUN: llc -march=amdgcn -mcpu=tahiti -verify-machineinstrs -enable-unsafe-fp-math < %s | FileCheck %s
; Run with unsafe-fp-math to make sure nothing tries to turn this into 1 / rsqrt(x)
; CHECK: {{^}}fsqrt_f32:
; CHECK: v_sqrt_f32_e32 {{v[0-9]+, v[0-9]+}}

36
test/CodeGen/R600/rsq.ll
View File

@ -1,6 +1,7 @@
; RUN: llc -march=amdgcn -mcpu=SI -mattr=-fp32-denormals -verify-machineinstrs -enable-unsafe-fp-math < %s | FileCheck -check-prefix=SI-UNSAFE -check-prefix=SI %s
; RUN: llc -march=amdgcn -mcpu=SI -mattr=-fp32-denormals -verify-machineinstrs < %s | FileCheck -check-prefix=SI-SAFE -check-prefix=SI %s
declare i32 @llvm.r600.read.tidig.x() nounwind readnone
declare float @llvm.sqrt.f32(float) nounwind readnone
declare double @llvm.sqrt.f64(double) nounwind readnone
@ -36,3 +37,38 @@ define void @rsq_f32_sgpr(float addrspace(1)* noalias %out, float %val) nounwind
store float %div, float addrspace(1)* %out, align 4
ret void
}
; Recognize that this is rsqrt(a) * rcp(b) * c,
; not 1 / ( 1 / sqrt(a)) * rcp(b) * c.
; SI-LABEL: @rsqrt_fmul
; SI-DAG: buffer_load_dword [[A:v[0-9]+]], {{v\[[0-9]+:[0-9]+\]}}, {{s\[[0-9]+:[0-9]+\]}}, 0 addr64{{$}}
; SI-DAG: buffer_load_dword [[B:v[0-9]+]], {{v\[[0-9]+:[0-9]+\]}}, {{s\[[0-9]+:[0-9]+\]}}, 0 addr64 offset:4
; SI-DAG: buffer_load_dword [[C:v[0-9]+]], {{v\[[0-9]+:[0-9]+\]}}, {{s\[[0-9]+:[0-9]+\]}}, 0 addr64 offset:8
; SI-UNSAFE-DAG: v_rsq_f32_e32 [[RSQA:v[0-9]+]], [[A]]
; SI-UNSAFE-DAG: v_rcp_f32_e32 [[RCPB:v[0-9]+]], [[B]]
; SI-UNSAFE-DAG: v_mul_f32_e32 [[TMP:v[0-9]+]], [[RCPB]], [[RSQA]]
; SI-UNSAFE: v_mul_f32_e32 [[RESULT:v[0-9]+]], [[TMP]], [[C]]
; SI-UNSAFE: buffer_store_dword [[RESULT]]
; SI-SAFE-NOT: v_rsq_f32
; SI: s_endpgm
define void @rsqrt_fmul(float addrspace(1)* %out, float addrspace(1)* %in) {
%tid = call i32 @llvm.r600.read.tidig.x() nounwind readnone
%out.gep = getelementptr float addrspace(1)* %out, i32 %tid
%gep.0 = getelementptr float addrspace(1)* %in, i32 %tid
%gep.1 = getelementptr float addrspace(1)* %gep.0, i32 1
%gep.2 = getelementptr float addrspace(1)* %gep.0, i32 2
%a = load float addrspace(1)* %gep.0
%b = load float addrspace(1)* %gep.1
%c = load float addrspace(1)* %gep.2
%x = call float @llvm.sqrt.f32(float %a)
%y = fmul float %x, %b
%z = fdiv float %c, %y
store float %z, float addrspace(1)* %out.gep
ret void
}