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DAGCombiner: Combine extract_vector_elt from build_vector 

This basic combine was surprisingly missing.
AMDGPU legalizes many operations in terms of 32-bit vector components,
so not doing this results in many extra copies and subregister extracts
that need to be cleaned up later.

InstCombine already does this for the hasOneUse case. The target hook
is to fix a handful of tests which break (e.g. ARM/vmov.ll) which turn
from a vector materialize repeated immediate instruction to a constant
vector load with more scalar copies from it.

llvm-svn: 250129
This commit is contained in:
Matt Arsenault 2015-10-12 23:59:50 +00:00
parent 82c00bee3c
commit 61dc235f20
9 changed files with 78 additions and 33 deletions
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6
llvm/include/llvm/Target/TargetLowering.h
View File

@ -1720,6 +1720,12 @@ public:
return false;
}
// Return true if it is profitable to use a scalar input to a BUILD_VECTOR
// even if the vector itself has multiple uses.
virtual bool aggressivelyPreferBuildVectorSources(EVT VecVT) const {
return false;
}
//===--------------------------------------------------------------------===//
// Runtime Library hooks
//

25
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -11886,7 +11886,24 @@ SDValue DAGCombiner::visitEXTRACT_VECTOR_ELT(SDNode *N) {
}
SDValue EltNo = N->getOperand(1);
bool ConstEltNo = isa<ConstantSDNode>(EltNo);
ConstantSDNode *ConstEltNo = dyn_cast<ConstantSDNode>(EltNo);
// extract_vector_elt (build_vector x, y), 1 -> y
if (ConstEltNo &&
InVec.getOpcode() == ISD::BUILD_VECTOR &&
TLI.isTypeLegal(VT) &&
(InVec.hasOneUse() ||
TLI.aggressivelyPreferBuildVectorSources(VT))) {
SDValue Elt = InVec.getOperand(ConstEltNo->getZExtValue());
EVT InEltVT = Elt.getValueType();
// Sometimes build_vector's scalar input types do not match result type.
if (NVT == InEltVT)
return Elt;
// TODO: It may be useful to truncate if free if the build_vector implicitly
// converts.
}
// Transform: (EXTRACT_VECTOR_ELT( VECTOR_SHUFFLE )) -> EXTRACT_VECTOR_ELT.
// We only perform this optimization before the op legalization phase because
@ -11894,13 +11911,11 @@ SDValue DAGCombiner::visitEXTRACT_VECTOR_ELT(SDNode *N) {
// patterns. For example on AVX, extracting elements from a wide vector
// without using extract_subvector. However, if we can find an underlying
// scalar value, then we can always use that.
if (InVec.getOpcode() == ISD::VECTOR_SHUFFLE
&& ConstEltNo) {
int Elt = cast<ConstantSDNode>(EltNo)->getZExtValue();
if (ConstEltNo && InVec.getOpcode() == ISD::VECTOR_SHUFFLE) {
int NumElem = VT.getVectorNumElements();
ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(InVec);
// Find the new index to extract from.
int OrigElt = SVOp->getMaskElt(Elt);
int OrigElt = SVOp->getMaskElt(ConstEltNo->getZExtValue());
// Extracting an undef index is undef.
if (OrigElt == -1)

12
llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
View File

@ -533,6 +533,18 @@ bool AMDGPUTargetLowering:: storeOfVectorConstantIsCheap(EVT MemVT,
return true;
}
bool AMDGPUTargetLowering::aggressivelyPreferBuildVectorSources(EVT VecVT) const {
// There are few operations which truly have vector input operands. Any vector
// operation is going to involve operations on each component, and a
// build_vector will be a copy per element, so it always makes sense to use a
// build_vector input in place of the extracted element to avoid a copy into a
// super register.
//
// We should probably only do this if all users are extracts only, but this
// should be the common case.
return true;
}
bool AMDGPUTargetLowering::isTruncateFree(EVT Source, EVT Dest) const {
// Truncate is just accessing a subregister.
return Dest.bitsLT(Source) && (Dest.getSizeInBits() % 32 == 0);

1
llvm/lib/Target/AMDGPU/AMDGPUISelLowering.h
View File

@ -138,6 +138,7 @@ public:
bool storeOfVectorConstantIsCheap(EVT MemVT,
unsigned NumElem,
unsigned AS) const override;
bool aggressivelyPreferBuildVectorSources(EVT VecVT) const override;
bool isCheapToSpeculateCttz() const override;
bool isCheapToSpeculateCtlz() const override;

3
llvm/test/CodeGen/AArch64/fold-constants.ll
View File

@ -3,9 +3,6 @@
define i64 @dotests_616() {
; CHECK-LABEL: dotests_616
; CHECK: movi d0, #0000000000000000
; CHECK-NEXT: umov w8, v0.b[2]
; CHECK-NEXT: sbfx w8, w8, #0, #1
; CHECK-NEXT: fmov s0, w8
; CHECK-NEXT: fmov x0, d0
; CHECK-NEXT: ret
entry:

6
llvm/test/CodeGen/AMDGPU/ds_read2.ll
View File

@ -216,10 +216,8 @@ define void @read2_ptr_is_subreg_arg_offset_f32(float addrspace(1)* %out, <2 x f
ret void
}
; We should be able to merge in this case, but probably not worth the effort.
; SI-NOT: ds_read2_b32
; SI: ds_read_b32
; SI: ds_read_b32
; SI-LABEL: {{^}}read2_ptr_is_subreg_f32:
; SI: ds_read2_b32 {{v\[[0-9]+:[0-9]+\]}}, {{v[0-9]+}} offset1:8{{$}}
; SI: s_endpgm
define void @read2_ptr_is_subreg_f32(float addrspace(1)* %out) #0 {
%x.i = tail call i32 @llvm.r600.read.tidig.x() #1

12
llvm/test/CodeGen/AMDGPU/fceil64.ll
View File

@ -17,12 +17,12 @@ declare <16 x double> @llvm.ceil.v16f64(<16 x double>) nounwind readnone
; SI: s_lshr_b64
; SI: s_not_b64
; SI: s_and_b64
; SI: cmp_gt_i32
; SI: cndmask_b32
; SI: cndmask_b32
; SI: cmp_lt_i32
; SI: cndmask_b32
; SI: cndmask_b32
; SI-DAG: cmp_gt_i32
; SI-DAG: cndmask_b32
; SI-DAG: cndmask_b32
; SI-DAG: cmp_lt_i32
; SI-DAG: cndmask_b32
; SI-DAG: cndmask_b32
; SI-DAG: v_cmp_lt_f64
; SI-DAG: v_cmp_lg_f64
; SI: s_and_b64

12
llvm/test/CodeGen/AMDGPU/ftrunc.f64.ll
View File

@ -29,12 +29,12 @@ define void @v_ftrunc_f64(double addrspace(1)* %out, double addrspace(1)* %in) {
; SI: s_lshr_b64
; SI: s_not_b64
; SI: s_and_b64
; SI: cmp_gt_i32
; SI: cndmask_b32
; SI: cndmask_b32
; SI: cmp_lt_i32
; SI: cndmask_b32
; SI: cndmask_b32
; SI-DAG: cmp_gt_i32
; SI-DAG: cndmask_b32
; SI-DAG: cndmask_b32
; SI-DAG: cmp_lt_i32
; SI-DAG: cndmask_b32
; SI-DAG: cndmask_b32
; SI: s_endpgm
define void @ftrunc_f64(double addrspace(1)* %out, double %x) {
%y = call double @llvm.trunc.f64(double %x) nounwind readnone

34
llvm/test/CodeGen/AMDGPU/gep-address-space.ll
View File

@ -11,24 +11,35 @@ define void @use_gep_address_space([1024 x i32] addrspace(3)* %array) nounwind {
ret void
}
define void @use_gep_address_space_large_offset([1024 x i32] addrspace(3)* %array) nounwind {
; CHECK-LABEL: {{^}}use_gep_address_space_large_offset:
; The LDS offset will be 65536 bytes, which is larger than the size of LDS on
; SI, which is why it is being OR'd with the base pointer.
; SI: s_or_b32
; CI: s_add_i32
; CHECK: ds_write_b32
define void @use_gep_address_space_large_offset([1024 x i32] addrspace(3)* %array) nounwind {
%p = getelementptr [1024 x i32], [1024 x i32] addrspace(3)* %array, i16 0, i16 16384
store i32 99, i32 addrspace(3)* %p
ret void
}
define void @gep_as_vector_v4(<4 x [1024 x i32] addrspace(3)*> %array) nounwind {
; CHECK-LABEL: {{^}}gep_as_vector_v4:
; CHECK: s_add_i32
; CHECK: s_add_i32
; CHECK: s_add_i32
; CHECK: s_add_i32
; SI: s_add_i32
; SI: s_add_i32
; SI: s_add_i32
; SI: s_add_i32
; CHECK-DAG: v_mov_b32_e32 {{v[0-9]+}}, {{s[0-9]+}}
; CHECK-DAG: v_mov_b32_e32 {{v[0-9]+}}, {{s[0-9]+}}
; CHECK-DAG: v_mov_b32_e32 {{v[0-9]+}}, {{s[0-9]+}}
; CHECK-DAG: v_mov_b32_e32 {{v[0-9]+}}, {{s[0-9]+}}
; CI-DAG: ds_write_b32 v{{[0-9]+}}, v{{[0-9]+}} offset:64
; CI-DAG: ds_write_b32 v{{[0-9]+}}, v{{[0-9]+}} offset:64
; CI-DAG: ds_write_b32 v{{[0-9]+}}, v{{[0-9]+}} offset:64
; CI-DAG: ds_write_b32 v{{[0-9]+}}, v{{[0-9]+}} offset:64
; CHECK: s_endpgm
define void @gep_as_vector_v4(<4 x [1024 x i32] addrspace(3)*> %array) nounwind {
%p = getelementptr [1024 x i32], <4 x [1024 x i32] addrspace(3)*> %array, <4 x i16> zeroinitializer, <4 x i16> <i16 16, i16 16, i16 16, i16 16>
%p0 = extractelement <4 x i32 addrspace(3)*> %p, i32 0
%p1 = extractelement <4 x i32 addrspace(3)*> %p, i32 1
@ -41,10 +52,15 @@ define void @gep_as_vector_v4(<4 x [1024 x i32] addrspace(3)*> %array) nounwind
ret void
}
define void @gep_as_vector_v2(<2 x [1024 x i32] addrspace(3)*> %array) nounwind {
; CHECK-LABEL: {{^}}gep_as_vector_v2:
; CHECK: s_add_i32
; CHECK: s_add_i32
; SI: s_add_i32
; SI: s_add_i32
; CHECK-DAG: v_mov_b32_e32 {{v[0-9]+}}, {{s[0-9]+}}
; CHECK-DAG: v_mov_b32_e32 {{v[0-9]+}}, {{s[0-9]+}}
; CI-DAG: ds_write_b32 v{{[0-9]+}}, v{{[0-9]+}} offset:64
; CI-DAG: ds_write_b32 v{{[0-9]+}}, v{{[0-9]+}} offset:64
; CHECK: s_endpgm
define void @gep_as_vector_v2(<2 x [1024 x i32] addrspace(3)*> %array) nounwind {
%p = getelementptr [1024 x i32], <2 x [1024 x i32] addrspace(3)*> %array, <2 x i16> zeroinitializer, <2 x i16> <i16 16, i16 16>
%p0 = extractelement <2 x i32 addrspace(3)*> %p, i32 0
%p1 = extractelement <2 x i32 addrspace(3)*> %p, i32 1