AMDGPU: Avoid using 64-bit shift for i64 (shl x, 32)

This can be done only with moves which theoretically
will optimize better later.

Although this transform increases the instruction count,
it should be code size / cycle count neutral in the worst
VALU case. It also seems to slightly improve a couple
of testcases due to other DAG combines this exposes.

This is probably slightly worse for the SALU case, so
it might be better to handle this during moveToVALU,
although then you lose some simplifications like
the load width reducing in the simple testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242177 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/AMDGPU/AMDGPUISelLowering.cpp b/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
index 3b68a92cd5f7a18f5e92109e0c27ea273cb83e43..3a65f3b56146d7b9cb208821201ee68a05f38304 100644 (file)
--- a/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
+++ b/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
@@ -406,6 +406,7 @@ AMDGPUTargetLowering::AMDGPUTargetLowering(TargetMachine &TM,
   setOperationAction(ISD::FNEARBYINT, MVT::f32, Custom);
   setOperationAction(ISD::FNEARBYINT, MVT::f64, Custom);
 
+  setTargetDAGCombine(ISD::SHL);
   setTargetDAGCombine(ISD::MUL);
   setTargetDAGCombine(ISD::SELECT);
   setTargetDAGCombine(ISD::SELECT_CC);
@@ -2415,6 +2416,33 @@ SDValue AMDGPUTargetLowering::performStoreCombine(SDNode *N,
                       SN->getBasePtr(), SN->getMemOperand());
 }
 
+SDValue AMDGPUTargetLowering::performShlCombine(SDNode *N,
+                                                DAGCombinerInfo &DCI) const {
+  if (N->getValueType(0) != MVT::i64)
+    return SDValue();
+
+  // i64 (shl x, 32) -> (build_pair 0, x)
+
+  // Doing this with moves theoretically helps MI optimizations that understand
+  // copies. 2 v_mov_b32_e32 will have the same code size / cycle count as
+  // v_lshl_b64. In the SALU case, I think this is slightly worse since it
+  // doubles the code size and I'm unsure about cycle count.
+  const ConstantSDNode *RHS = dyn_cast<ConstantSDNode>(N->getOperand(1));
+  if (!RHS || RHS->getZExtValue() != 32)
+    return SDValue();
+
+  SDValue LHS = N->getOperand(0);
+
+  SDLoc SL(N);
+  SelectionDAG &DAG = DCI.DAG;
+
+  // Extract low 32-bits.
+  SDValue Lo = DAG.getNode(ISD::TRUNCATE, SL, MVT::i32, LHS);
+
+  const SDValue Zero = DAG.getConstant(0, SL, MVT::i32);
+  return DAG.getNode(ISD::BUILD_PAIR, SL, MVT::i64, Zero, Lo);
+}
+
 SDValue AMDGPUTargetLowering::performMulCombine(SDNode *N,
                                                 DAGCombinerInfo &DCI) const {
   EVT VT = N->getValueType(0);
@@ -2454,6 +2482,12 @@ SDValue AMDGPUTargetLowering::PerformDAGCombine(SDNode *N,
   switch(N->getOpcode()) {
   default:
     break;
+  case ISD::SHL: {
+    if (DCI.getDAGCombineLevel() < AfterLegalizeDAG)
+      break;
+
+    return performShlCombine(N, DCI);
+  }
   case ISD::MUL:
     return performMulCombine(N, DCI);
   case AMDGPUISD::MUL_I24:

diff --git a/lib/Target/AMDGPU/AMDGPUISelLowering.h b/lib/Target/AMDGPU/AMDGPUISelLowering.h
index bba303d3e4be2e9db85ad00e8b0b35dd43a11b35..478b2035fd753f55f6e999e29cb1b0faf3bb3a41 100644 (file)
--- a/lib/Target/AMDGPU/AMDGPUISelLowering.h
+++ b/lib/Target/AMDGPU/AMDGPUISelLowering.h
@@ -65,6 +65,7 @@ private:
   SDValue LowerSIGN_EXTEND_INREG(SDValue Op, SelectionDAG &DAG) const;
 
   SDValue performStoreCombine(SDNode *N, DAGCombinerInfo &DCI) const;
+  SDValue performShlCombine(SDNode *N, DAGCombinerInfo &DCI) const;
   SDValue performMulCombine(SDNode *N, DAGCombinerInfo &DCI) const;
 
 protected:

diff --git a/test/CodeGen/AMDGPU/array-ptr-calc-i64.ll b/test/CodeGen/AMDGPU/array-ptr-calc-i64.ll
index eae095eb8449df340738e2dbe03efd0eae6a4835..a3ae3c3aea1675289652fcc9c52b7a09dd1ba488 100644 (file)
--- a/test/CodeGen/AMDGPU/array-ptr-calc-i64.ll
+++ b/test/CodeGen/AMDGPU/array-ptr-calc-i64.ll
@@ -3,8 +3,9 @@
 declare i32 @llvm.SI.tid() readnone
 
 ; SI-LABEL: {{^}}test_array_ptr_calc:
-; SI: v_mul_lo_i32
-; SI: v_mul_hi_i32
+; SI-DAG: v_mul_lo_i32
+; SI-DAG: v_mul_hi_i32
+; SI: s_endpgm
 define void @test_array_ptr_calc(i32 addrspace(1)* noalias %out, [1025 x i32] addrspace(1)* noalias %inA, i32 addrspace(1)* noalias %inB) {
   %tid = call i32 @llvm.SI.tid() readnone
   %a_ptr = getelementptr [1025 x i32], [1025 x i32] addrspace(1)* %inA, i32 %tid, i32 0

diff --git a/test/CodeGen/AMDGPU/mul_uint24.ll b/test/CodeGen/AMDGPU/mul_uint24.ll
index e640a7cd69f6d953a62430a0bed9cb4bfd68f2f3..8a0e71d739bee424c2c34b07ee345570b017c732 100644 (file)
--- a/test/CodeGen/AMDGPU/mul_uint24.ll
+++ b/test/CodeGen/AMDGPU/mul_uint24.ll
@@ -52,16 +52,18 @@ entry:
 ; FUNC_LABEL: {{^}}mul24_i64:
 ; EG; MUL_UINT24
 ; EG: MULHI
-; SI: v_mul_u32_u24
 ; FIXME: SI support 24-bit mulhi
-; SI: v_mul_hi_u32
-define void @mul24_i64(i64 addrspace(1)* %out, i64 %a, i64 %b) {
+
+; SI-DAG: v_mul_u32_u24
+; SI-DAG: v_mul_hi_u32
+; SI: s_endpgm
+define void @mul24_i64(i64 addrspace(1)* %out, i64 %a, i64 %b, i64 %c) {
 entry:
-  %0 = shl i64 %a, 40
-  %a_24 = lshr i64 %0, 40
-  %1 = shl i64 %b, 40
-  %b_24 = lshr i64 %1, 40
-  %2 = mul i64 %a_24, %b_24
-  store i64 %2, i64 addrspace(1)* %out
+  %tmp0 = shl i64 %a, 40
+  %a_24 = lshr i64 %tmp0, 40
+  %tmp1 = shl i64 %b, 40
+  %b_24 = lshr i64 %tmp1, 40
+  %tmp2 = mul i64 %a_24, %b_24
+  store i64 %tmp2, i64 addrspace(1)* %out
   ret void
 }

diff --git a/test/CodeGen/AMDGPU/shl.ll b/test/CodeGen/AMDGPU/shl.ll
index 53b63dc4b8adb866ed88ac906fcea3225a3f58f8..6f81a39ed96aa5c85053f7e72e254166d23e0070 100644 (file)
--- a/test/CodeGen/AMDGPU/shl.ll
+++ b/test/CodeGen/AMDGPU/shl.ll
@@ -1,6 +1,9 @@
-;RUN: llc < %s -march=r600 -mcpu=redwood | FileCheck --check-prefix=EG %s
-;RUN: llc < %s -march=amdgcn -mcpu=verde -verify-machineinstrs | FileCheck --check-prefix=SI %s
-;RUN: llc < %s -march=amdgcn -mcpu=tonga -verify-machineinstrs | FileCheck --check-prefix=VI %s
+; RUN: llc < %s -march=r600 -mcpu=redwood | FileCheck --check-prefix=EG %s
+; RUN: llc < %s -march=amdgcn -mcpu=verde -verify-machineinstrs | FileCheck -check-prefix=GCN -check-prefix=SI %s
+; XUN: llc < %s -march=amdgcn -mcpu=tonga -verify-machineinstrs | FileCheck -check-prefix=GCN -check-prefix=VI %s
+
+declare i32 @llvm.r600.read.tidig.x() #0
+
 
 ;EG: {{^}}shl_v2i32:
 ;EG: LSHL {{\*? *}}T{{[0-9]+\.[XYZW], T[0-9]+\.[XYZW], T[0-9]+\.[XYZW]}}
@@ -178,3 +181,32 @@ define void @shl_v4i64(<4 x i64> addrspace(1)* %out, <4 x i64> addrspace(1)* %in
   store <4 x i64> %result, <4 x i64> addrspace(1)* %out
   ret void
 }
+
+; Make sure load width gets reduced to i32 load.
+; GCN-LABEL: {{^}}s_shl_32_i64:
+; GCN-DAG: s_load_dword [[LO_A:s[0-9]+]], s{{\[[0-9]+:[0-9]+\]}}, 0xb{{$}}
+; GCN-DAG: s_mov_b32 s[[SLO:[0-9]+]], 0{{$}}
+; GCN-DAG: v_mov_b32_e32 v[[VLO:[0-9]+]], s[[SLO]]
+; GCN-DAG: v_mov_b32_e32 v[[VHI:[0-9]+]], [[LO_A]]
+; GCN: buffer_store_dwordx2 v{{\[}}[[VLO]]:[[VHI]]{{\]}}
+define void @s_shl_32_i64(i64 addrspace(1)* %out, i64 %a) {
+  %result = shl i64 %a, 32
+  store i64 %result, i64 addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}v_shl_32_i64:
+; GCN-DAG: buffer_load_dword v[[LO_A:[0-9]+]],
+; GCN-DAG: v_mov_b32_e32 v[[VLO:[0-9]+]], 0{{$}}
+; GCN: buffer_store_dwordx2 v{{\[}}[[VLO]]:[[LO_A]]{{\]}}
+define void @v_shl_32_i64(i64 addrspace(1)* %out, i64 addrspace(1)* %in) {
+  %tid = call i32 @llvm.r600.read.tidig.x() #0
+  %gep.in = getelementptr i64, i64 addrspace(1)* %in, i32 %tid
+  %gep.out = getelementptr i64, i64 addrspace(1)* %out, i32 %tid
+  %a = load i64, i64 addrspace(1)* %gep.in
+  %result = shl i64 %a, 32
+  store i64 %result, i64 addrspace(1)* %gep.out
+  ret void
+}
+
+attributes #0 = { nounwind readnone }

diff --git a/test/CodeGen/AMDGPU/srl.ll b/test/CodeGen/AMDGPU/srl.ll
index 4904d7fa1bd0ce7752f56027ef73e6c53d593e25..0dad91e709d995ef74c04b06648855c2d8421ab6 100644 (file)
--- a/test/CodeGen/AMDGPU/srl.ll
+++ b/test/CodeGen/AMDGPU/srl.ll
@@ -1,7 +1,9 @@
-; RUN: llc -march=amdgcn -mcpu=verde -verify-machineinstrs < %s | FileCheck -check-prefix=SI -check-prefix=FUNC %s
-; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs < %s | FileCheck -check-prefix=VI -check-prefix=FUNC %s
+; RUN: llc -march=amdgcn -mcpu=verde -verify-machineinstrs < %s | FileCheck -check-prefix=SI -check-prefix=GCN -check-prefix=FUNC %s
+; XUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs < %s | FileCheck -check-prefix=VI -check-prefix=GCN -check-prefix=FUNC %s
 ; RUN: llc -march=r600 -mcpu=redwood < %s | FileCheck -check-prefix=EG -check-prefix=FUNC %s
 
+declare i32 @llvm.r600.read.tidig.x() #0
+
 ; FUNC-LABEL: {{^}}lshr_i32:
 ; SI: v_lshrrev_b32_e32 v{{[0-9]+, v[0-9]+, v[0-9]+}}
 ; VI: v_lshrrev_b32_e32 v{{[0-9]+, v[0-9]+, v[0-9]+}}
@@ -184,3 +186,32 @@ define void @lshr_v4i64(<4 x i64> addrspace(1)* %out, <4 x i64> addrspace(1)* %i
   store <4 x i64> %result, <4 x i64> addrspace(1)* %out
   ret void
 }
+
+; Make sure load width gets reduced to i32 load.
+; GCN-LABEL: {{^}}s_lshr_32_i64:
+; GCN-DAG: s_load_dword [[HI_A:s[0-9]+]], s{{\[[0-9]+:[0-9]+\]}}, 0xc{{$}}
+; GCN-DAG: s_mov_b32 s[[SHI:[0-9]+]], 0{{$}}
+; GCN-DAG: v_mov_b32_e32 v[[VHI:[0-9]+]], s[[SHI]]
+; GCN-DAG: v_mov_b32_e32 v[[VLO:[0-9]+]], [[HI_A]]
+; GCN: buffer_store_dwordx2 v{{\[}}[[VLO]]:[[VHI]]{{\]}}
+define void @s_lshr_32_i64(i64 addrspace(1)* %out, i64 %a) {
+  %result = lshr i64 %a, 32
+  store i64 %result, i64 addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}v_lshr_32_i64:
+; GCN-DAG: buffer_load_dword v[[HI_A:[0-9]+]], v{{\[[0-9]+:[0-9]+\]}}, s{{\[[0-9]+:[0-9]+\]}}, 0 addr64 offset:4
+; GCN-DAG: v_mov_b32_e32 v[[VHI:[0-9]+]], 0{{$}}
+; GCN: buffer_store_dwordx2 v{{\[}}[[HI_A]]:[[VHI]]{{\]}}
+define void @v_lshr_32_i64(i64 addrspace(1)* %out, i64 addrspace(1)* %in) {
+  %tid = call i32 @llvm.r600.read.tidig.x() #0
+  %gep.in = getelementptr i64, i64 addrspace(1)* %in, i32 %tid
+  %gep.out = getelementptr i64, i64 addrspace(1)* %out, i32 %tid
+  %a = load i64, i64 addrspace(1)* %gep.in
+  %result = lshr i64 %a, 32
+  store i64 %result, i64 addrspace(1)* %gep.out
+  ret void
+}
+
+attributes #0 = { nounwind readnone }