From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Wed, 8 May 2019 15:49:10 +0000 (+0000)
Subject: [AMDGPU] Reapplied BFE canonicalization from D60462
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bba36ee9e9211eb9986466a65abcf35691180c01;p=llvm

[AMDGPU] Reapplied BFE canonicalization from D60462

This was committed in rL358887 but reverted in rL360066 due to a x86 regression, really it should be have been pre-committed instead of being part of the SimplifyDemandedBits bitcast patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@360263 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/AMDGPU/AMDGPUISelLowering.cpp b/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
index 994e912ac9c..409fbfa22f3 100644
--- a/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
+++ b/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
@@ -3202,30 +3202,44 @@ SDValue AMDGPUTargetLowering::performSraCombine(SDNode *N,
 
 SDValue AMDGPUTargetLowering::performSrlCombine(SDNode *N,
                                                 DAGCombinerInfo &DCI) const {
-  if (N->getValueType(0) != MVT::i64)
-    return SDValue();
-
-  const ConstantSDNode *RHS = dyn_cast<ConstantSDNode>(N->getOperand(1));
+  auto *RHS = dyn_cast<ConstantSDNode>(N->getOperand(1));
   if (!RHS)
     return SDValue();
 
+  EVT VT = N->getValueType(0);
+  SDValue LHS = N->getOperand(0);
   unsigned ShiftAmt = RHS->getZExtValue();
+  SelectionDAG &DAG = DCI.DAG;
+  SDLoc SL(N);
+
+  // fold (srl (and x, c1 << c2), c2) -> (and (srl(x, c2), c1)
+  // this improves the ability to match BFE patterns in isel.
+  if (LHS.getOpcode() == ISD::AND) {
+    if (auto *Mask = dyn_cast<ConstantSDNode>(LHS.getOperand(1))) {
+      if (Mask->getAPIntValue().isShiftedMask() &&
+          Mask->getAPIntValue().countTrailingZeros() == ShiftAmt) {
+        return DAG.getNode(
+            ISD::AND, SL, VT,
+            DAG.getNode(ISD::SRL, SL, VT, LHS.getOperand(0), N->getOperand(1)),
+            DAG.getNode(ISD::SRL, SL, VT, LHS.getOperand(1), N->getOperand(1)));
+      }
+    }
+  }
+
+  if (VT != MVT::i64)
+    return SDValue();
+
   if (ShiftAmt < 32)
     return SDValue();
 
   // srl i64:x, C for C >= 32
   // =>
   //   build_pair (srl hi_32(x), C - 32), 0
-
-  SelectionDAG &DAG = DCI.DAG;
-  SDLoc SL(N);
-
   SDValue One = DAG.getConstant(1, SL, MVT::i32);
   SDValue Zero = DAG.getConstant(0, SL, MVT::i32);
 
-  SDValue VecOp = DAG.getNode(ISD::BITCAST, SL, MVT::v2i32, N->getOperand(0));
-  SDValue Hi = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, SL, MVT::i32,
-                           VecOp, One);
+  SDValue VecOp = DAG.getNode(ISD::BITCAST, SL, MVT::v2i32, LHS);
+  SDValue Hi = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, SL, MVT::i32, VecOp, One);
 
   SDValue NewConst = DAG.getConstant(ShiftAmt - 32, SL, MVT::i32);
   SDValue NewShift = DAG.getNode(ISD::SRL, SL, MVT::i32, Hi, NewConst);
diff --git a/test/CodeGen/AMDGPU/store-weird-sizes.ll b/test/CodeGen/AMDGPU/store-weird-sizes.ll
index 13380e03e32..f5857a330fa 100644
--- a/test/CodeGen/AMDGPU/store-weird-sizes.ll
+++ b/test/CodeGen/AMDGPU/store-weird-sizes.ll
@@ -86,8 +86,8 @@ define amdgpu_kernel void @local_store_i55(i55 addrspace(3)* %ptr, i55 %arg) #0
 ; GFX9-NEXT:    v_mov_b32_e32 v2, s2
 ; GFX9-NEXT:    ds_write_b16 v1, v2 offset:4
 ; GFX9-NEXT:    s_waitcnt vmcnt(0)
-; GFX9-NEXT:    v_and_b32_e32 v0, 0x7f0000, v0
-; GFX9-NEXT:    ds_write_b8_d16_hi v1, v0 offset:6
+; GFX9-NEXT:    v_bfe_u32 v0, v0, 16, 7
+; GFX9-NEXT:    ds_write_b8 v1, v0 offset:6
 ; GFX9-NEXT:    ds_write_b32 v1, v3
 ; GFX9-NEXT:    s_endpgm
   store i55 %arg, i55 addrspace(3)* %ptr, align 8