From 967325b373cd525ac09d67fc0582bde79a17d1f0 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Wed, 7 Dec 2016 16:28:21 +0000
Subject: [PATCH] [SelectionDAG] Add knownbits support for EXTRACT_VECTOR_ELT
 opcodes

llvm-svn: 288916
---
 llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 36 ++++++++++++++++++++++++++
 llvm/test/CodeGen/X86/known-bits-vector.ll     | 12 ++-------
 2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 66c4a5d..35e5f7a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2590,6 +2590,42 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
     }
     break;
   }
+  case ISD::INSERT_VECTOR_ELT: {
+    SDValue InVec = Op.getOperand(0);
+    SDValue InVal = Op.getOperand(1);
+    SDValue EltNo = Op.getOperand(2);
+
+    ConstantSDNode *CEltNo = dyn_cast<ConstantSDNode>(EltNo);
+    if (CEltNo && CEltNo->getAPIntValue().ult(NumElts)) {
+      // If we know the element index, split the demand between the
+      // source vector and the inserted element.
+      KnownZero = KnownOne = APInt::getAllOnesValue(BitWidth);
+      unsigned EltIdx = CEltNo->getZExtValue();
+
+      // If we demand the inserted element then add its common known bits.
+      if (DemandedElts[EltIdx]) {
+        computeKnownBits(InVal, KnownZero2, KnownOne2, Depth + 1);
+        KnownOne &= KnownOne2.zextOrTrunc(KnownOne.getBitWidth());
+        KnownZero &= KnownZero2.zextOrTrunc(KnownZero.getBitWidth());;
+      }
+
+      // If we demand the source vector then add its common known bits, ensuring
+      // that we don't demand the inserted element.
+      APInt VectorElts = DemandedElts & ~(APInt::getOneBitSet(NumElts, EltIdx));
+      if (!!VectorElts) {
+        computeKnownBits(InVec, KnownZero2, KnownOne2, VectorElts, Depth + 1);
+        KnownOne &= KnownOne2;
+        KnownZero &= KnownZero2;
+      }
+    } else {
+      // Unknown element index, so ignore DemandedElts and demand them all.
+      computeKnownBits(InVec, KnownZero, KnownOne, Depth + 1);
+      computeKnownBits(InVal, KnownZero2, KnownOne2, Depth + 1);
+      KnownOne &= KnownOne2.zextOrTrunc(KnownOne.getBitWidth());
+      KnownZero &= KnownZero2.zextOrTrunc(KnownZero.getBitWidth());;
+    }
+    break;
+  }
   case ISD::BSWAP: {
     computeKnownBits(Op.getOperand(0), KnownZero2, KnownOne2, DemandedElts,
                      Depth + 1);
diff --git a/llvm/test/CodeGen/X86/known-bits-vector.ll b/llvm/test/CodeGen/X86/known-bits-vector.ll
index 516bb2c..90316fa 100644
--- a/llvm/test/CodeGen/X86/known-bits-vector.ll
+++ b/llvm/test/CodeGen/X86/known-bits-vector.ll
@@ -58,11 +58,7 @@ define <4 x float> @knownbits_insert_uitofp(<4 x i32> %a0, i16 %a1, i16 %a2) nou
 ; X32-NEXT:    vpinsrd $0, %eax, %xmm0, %xmm0
 ; X32-NEXT:    vpinsrd $2, %ecx, %xmm0, %xmm0
 ; X32-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[0,0,2,2]
-; X32-NEXT:    vpblendw {{.*#+}} xmm1 = xmm0[0],mem[1],xmm0[2],mem[3],xmm0[4],mem[5],xmm0[6],mem[7]
-; X32-NEXT:    vpsrld $16, %xmm0, %xmm0
-; X32-NEXT:    vpblendw {{.*#+}} xmm0 = xmm0[0],mem[1],xmm0[2],mem[3],xmm0[4],mem[5],xmm0[6],mem[7]
-; X32-NEXT:    vaddps {{\.LCPI.*}}, %xmm0, %xmm0
-; X32-NEXT:    vaddps %xmm0, %xmm1, %xmm0
+; X32-NEXT:    vcvtdq2ps %xmm0, %xmm0
 ; X32-NEXT:    retl
 ;
 ; X64-LABEL: knownbits_insert_uitofp:
@@ -72,11 +68,7 @@ define <4 x float> @knownbits_insert_uitofp(<4 x i32> %a0, i16 %a1, i16 %a2) nou
 ; X64-NEXT:    vpinsrd $0, %eax, %xmm0, %xmm0
 ; X64-NEXT:    vpinsrd $2, %ecx, %xmm0, %xmm0
 ; X64-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[0,0,2,2]
-; X64-NEXT:    vpblendw {{.*#+}} xmm1 = xmm0[0],mem[1],xmm0[2],mem[3],xmm0[4],mem[5],xmm0[6],mem[7]
-; X64-NEXT:    vpsrld $16, %xmm0, %xmm0
-; X64-NEXT:    vpblendw {{.*#+}} xmm0 = xmm0[0],mem[1],xmm0[2],mem[3],xmm0[4],mem[5],xmm0[6],mem[7]
-; X64-NEXT:    vaddps {{.*}}(%rip), %xmm0, %xmm0
-; X64-NEXT:    vaddps %xmm0, %xmm1, %xmm0
+; X64-NEXT:    vcvtdq2ps %xmm0, %xmm0
 ; X64-NEXT:    retq
   %1 = zext i16 %a1 to i32
   %2 = zext i16 %a2 to i32
-- 
2.7.4