[X86] Teach the DAGCombiner how to fold a OR of two shufflevector nodes.

This patch teaches the DAGCombiner how to fold a binary OR between two
shufflevector into a single shuffle vector when possible.

The rules are:
  1. fold (or (shuf A, V_0, MA), (shuf B, V_0, MB)) -> (shuf A, B, Mask1)
  2. fold (or (shuf A, V_0, MA), (shuf B, V_0, MB)) -> (shuf B, A, Mask2)

The DAGCombiner can take advantage of the fact that OR is commutative and
compute two possible shuffle masks (Mask1 and Mask2) for the resulting
shuffle node.

Before folding a dag according to either rule 1 or 2, DAGCombiner verifies
that the resulting shuffle mask is legal for the target.
DAGCombiner would firstly try to fold according to 1.; If not possible
then it will try to fold according to 2.
If both Mask1 and Mask2 are illegal then we conservatively don't fold
the OR instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203156 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 8650154c1a90358a7560ece2f5d128da2c652bd1..aa35f6d3e77156c6f2a2af33d0d01c5d1dcf28e0 100644 (file)
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3200,6 +3200,60 @@ SDValue DAGCombiner::visitOR(SDNode *N) {
       return N0;
     if (ISD::isBuildVectorAllOnes(N1.getNode()))
       return N1;
+
+    // fold (or (shuf A, V_0, MA), (shuf B, V_0, MB)) -> (shuf A, B, Mask1)
+    // fold (or (shuf A, V_0, MA), (shuf B, V_0, MB)) -> (shuf B, A, Mask2)
+    // Do this only if the resulting shuffle is legal.
+    if (isa<ShuffleVectorSDNode>(N0) &&
+        isa<ShuffleVectorSDNode>(N1) &&
+        N0->getOperand(1) == N1->getOperand(1) &&
+        ISD::isBuildVectorAllZeros(N0.getOperand(1).getNode())) {
+      bool CanFold = true;
+      unsigned NumElts = VT.getVectorNumElements();
+      const ShuffleVectorSDNode *SV0 = cast<ShuffleVectorSDNode>(N0);
+      const ShuffleVectorSDNode *SV1 = cast<ShuffleVectorSDNode>(N1);
+      // We construct two shuffle masks:
+      // - Mask1 is a shuffle mask for a shuffle with N0 as the first operand
+      // and N1 as the second operand.
+      // - Mask2 is a shuffle mask for a shuffle with N1 as the first operand
+      // and N0 as the second operand.
+      // We do this because OR is commutable and therefore there might be
+      // two ways to fold this node into a shuffle.
+      SmallVector<int,4> Mask1;
+      SmallVector<int,4> Mask2;
+      
+      for (unsigned i = 0; i != NumElts && CanFold; ++i) {
+        int M0 = SV0->getMaskElt(i);
+        int M1 = SV1->getMaskElt(i);
+   
+        // Both shuffle indexes are undef. Propagate Undef.
+        if (M0 < 0 && M1 < 0) {
+          Mask1.push_back(M0);
+          Mask2.push_back(M0);
+          continue;
+        }
+
+        if (M0 < 0 || M1 < 0 ||
+            (M0 < (int)NumElts && M1 < (int)NumElts) ||
+            (M0 >= (int)NumElts && M1 >= (int)NumElts)) {
+          CanFold = false;
+          break;
+        }
+        
+        Mask1.push_back(M0 < (int)NumElts ? M0 : M1 + NumElts);
+        Mask2.push_back(M1 < (int)NumElts ? M1 : M0 + NumElts);
+      }
+
+      if (CanFold) {
+        // Fold this sequence only if the resulting shuffle is 'legal'.
+        if (TLI.isShuffleMaskLegal(Mask1, VT))
+          return DAG.getVectorShuffle(VT, SDLoc(N), N0->getOperand(0),
+                                      N1->getOperand(0), &Mask1[0]);
+        if (TLI.isShuffleMaskLegal(Mask2, VT))
+          return DAG.getVectorShuffle(VT, SDLoc(N), N1->getOperand(0),
+                                      N0->getOperand(0), &Mask2[0]);
+      }
+    }
   }
 
   // fold (or x, undef) -> -1

diff --git a/test/CodeGen/X86/combine-or.ll b/test/CodeGen/X86/combine-or.ll
new file mode 100644 (file)
index 0000000..60b6d75
--- /dev/null
+++ b/test/CodeGen/X86/combine-or.ll
@@ -0,0 +1,267 @@
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -mcpu=corei7 | FileCheck %s
+
+
+; Verify that each of the following test cases is folded into a single
+; instruction which performs a blend operation.
+
+define <2 x i64> @test1(<2 x i64> %a, <2 x i64> %b) {
+  %shuf1 = shufflevector <2 x i64> %a, <2 x i64> zeroinitializer, <2 x i32><i32 0, i32 2>
+  %shuf2 = shufflevector <2 x i64> %b, <2 x i64> zeroinitializer, <2 x i32><i32 2, i32 1>
+  %or = or <2 x i64> %shuf1, %shuf2
+  ret <2 x i64> %or
+}
+; CHECK-LABEL: test1
+; CHECK-NOT: xorps
+; CHECK: movsd
+; CHECK-NOT: orps
+; CHECK: ret
+
+
+define <4 x i32> @test2(<4 x i32> %a, <4 x i32> %b) {
+  %shuf1 = shufflevector <4 x i32> %a, <4 x i32> zeroinitializer, <4 x i32><i32 4, i32 4, i32 2, i32 3>
+  %shuf2 = shufflevector <4 x i32> %b, <4 x i32> zeroinitializer, <4 x i32><i32 0, i32 1, i32 4, i32 4>
+  %or = or <4 x i32> %shuf1, %shuf2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test2
+; CHECK-NOT: xorps
+; CHECK: shufps
+; CHECK: ret
+
+
+define <2 x i64> @test3(<2 x i64> %a, <2 x i64> %b) {
+  %shuf1 = shufflevector <2 x i64> %a, <2 x i64> zeroinitializer, <2 x i32><i32 2, i32 1>
+  %shuf2 = shufflevector <2 x i64> %b, <2 x i64> zeroinitializer, <2 x i32><i32 0, i32 2>
+  %or = or <2 x i64> %shuf1, %shuf2
+  ret <2 x i64> %or
+}
+; CHECK-LABEL: test3
+; CHECK-NOT: xorps
+; CHECK: movsd
+; CHECK-NEXT: ret
+
+
+define <4 x i32> @test4(<4 x i32> %a, <4 x i32> %b) {
+  %shuf1 = shufflevector <4 x i32> %a, <4 x i32> zeroinitializer, <4 x i32><i32 0, i32 4, i32 4, i32 4>
+  %shuf2 = shufflevector <4 x i32> %b, <4 x i32> zeroinitializer, <4 x i32><i32 4, i32 1, i32 2, i32 3>
+  %or = or <4 x i32> %shuf1, %shuf2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test4
+; CHECK-NOT: xorps
+; CHECK: movss
+; CHECK-NOT: orps
+; CHECK: ret
+
+
+define <4 x i32> @test5(<4 x i32> %a, <4 x i32> %b) {
+  %shuf1 = shufflevector <4 x i32> %a, <4 x i32> zeroinitializer, <4 x i32><i32 4, i32 1, i32 2, i32 3>
+  %shuf2 = shufflevector <4 x i32> %b, <4 x i32> zeroinitializer, <4 x i32><i32 0, i32 4, i32 4, i32 4>
+  %or = or <4 x i32> %shuf1, %shuf2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test5
+; CHECK-NOT: xorps
+; CHECK: movss
+; CHECK-NEXT: ret
+
+
+define <4 x i32> @test6(<4 x i32> %a, <4 x i32> %b) {
+  %shuf1 = shufflevector <4 x i32> %a, <4 x i32> zeroinitializer, <4 x i32><i32 0, i32 1, i32 4, i32 4>
+  %shuf2 = shufflevector <4 x i32> %b, <4 x i32> zeroinitializer, <4 x i32><i32 4, i32 4, i32 2, i32 3>
+  %or = or <4 x i32> %shuf1, %shuf2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test6
+; CHECK-NOT: xorps
+; CHECK: shufps
+; CHECK-NEXT: ret
+
+
+define <4 x i32> @test7(<4 x i32> %a, <4 x i32> %b) {
+  %and1 = and <4 x i32> %a, <i32 -1, i32 -1, i32 0, i32 0>
+  %and2 = and <4 x i32> %b, <i32 0, i32 0, i32 -1, i32 -1>
+  %or = or <4 x i32> %and1, %and2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test7
+; CHECK-NOT: xorps
+; CHECK: shufps
+; CHECK-NEXT: ret
+
+
+define <2 x i64> @test8(<2 x i64> %a, <2 x i64> %b) {
+  %and1 = and <2 x i64> %a, <i64 -1, i64 0>
+  %and2 = and <2 x i64> %b, <i64 0, i64 -1>
+  %or = or <2 x i64> %and1, %and2
+  ret <2 x i64> %or
+}
+; CHECK-LABEL: test8
+; CHECK-NOT: xorps
+; CHECK: movsd
+; CHECK-NOT: orps
+; CHECK: ret
+
+
+define <4 x i32> @test9(<4 x i32> %a, <4 x i32> %b) {
+  %and1 = and <4 x i32> %a, <i32 0, i32 0, i32 -1, i32 -1>
+  %and2 = and <4 x i32> %b, <i32 -1, i32 -1, i32 0, i32 0>
+  %or = or <4 x i32> %and1, %and2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test9
+; CHECK-NOT: xorps
+; CHECK: shufps
+; CHECK: ret
+
+
+define <2 x i64> @test10(<2 x i64> %a, <2 x i64> %b) {
+  %and1 = and <2 x i64> %a, <i64 0, i64 -1>
+  %and2 = and <2 x i64> %b, <i64 -1, i64 0>
+  %or = or <2 x i64> %and1, %and2
+  ret <2 x i64> %or
+}
+; CHECK-LABEL: test10
+; CHECK-NOT: xorps
+; CHECK: movsd
+; CHECK-NEXT: ret
+
+
+define <4 x i32> @test11(<4 x i32> %a, <4 x i32> %b) {
+  %and1 = and <4 x i32> %a, <i32 -1, i32 0, i32 0, i32 0>
+  %and2 = and <4 x i32> %b, <i32 0, i32 -1, i32 -1, i32 -1>
+  %or = or <4 x i32> %and1, %and2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test11
+; CHECK-NOT: xorps
+; CHECK: movss
+; CHECK-NOT: orps
+; CHECK: ret
+
+
+define <4 x i32> @test12(<4 x i32> %a, <4 x i32> %b) {
+  %and1 = and <4 x i32> %a, <i32 0, i32 -1, i32 -1, i32 -1>
+  %and2 = and <4 x i32> %b, <i32 -1, i32 0, i32 0, i32 0>
+  %or = or <4 x i32> %and1, %and2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test12
+; CHECK-NOT: xorps
+; CHECK: movss
+; CHECK-NEXT: ret
+
+
+; Verify that the following test cases are folded into single shuffles.
+
+define <4 x i32> @test13(<4 x i32> %a, <4 x i32> %b) {
+  %shuf1 = shufflevector <4 x i32> %a, <4 x i32> zeroinitializer, <4 x i32><i32 1, i32 1, i32 4, i32 4>
+  %shuf2 = shufflevector <4 x i32> %b, <4 x i32> zeroinitializer, <4 x i32><i32 4, i32 4, i32 2, i32 3>
+  %or = or <4 x i32> %shuf1, %shuf2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test13
+; CHECK-NOT: xorps
+; CHECK: shufps
+; CHECK-NEXT: ret
+
+
+define <2 x i64> @test14(<2 x i64> %a, <2 x i64> %b) {
+  %shuf1 = shufflevector <2 x i64> %a, <2 x i64> zeroinitializer, <2 x i32><i32 0, i32 2>
+  %shuf2 = shufflevector <2 x i64> %b, <2 x i64> zeroinitializer, <2 x i32><i32 2, i32 0>
+  %or = or <2 x i64> %shuf1, %shuf2
+  ret <2 x i64> %or
+}
+; CHECK-LABEL: test14
+; CHECK-NOT: pslldq
+; CHECK-NOT: por
+; CHECK: punpcklqdq
+; CHECK-NEXT: ret
+
+
+define <4 x i32> @test15(<4 x i32> %a, <4 x i32> %b) {
+  %shuf1 = shufflevector <4 x i32> %a, <4 x i32> zeroinitializer, <4 x i32><i32 4, i32 4, i32 2, i32 1>
+  %shuf2 = shufflevector <4 x i32> %b, <4 x i32> zeroinitializer, <4 x i32><i32 2, i32 1, i32 4, i32 4>
+  %or = or <4 x i32> %shuf1, %shuf2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test15
+; CHECK-NOT: xorps
+; CHECK: shufps
+; CHECK-NOT: shufps
+; CHECK-NOT: orps
+; CHECK: ret
+
+
+define <2 x i64> @test16(<2 x i64> %a, <2 x i64> %b) {
+  %shuf1 = shufflevector <2 x i64> %a, <2 x i64> zeroinitializer, <2 x i32><i32 2, i32 0>
+  %shuf2 = shufflevector <2 x i64> %b, <2 x i64> zeroinitializer, <2 x i32><i32 0, i32 2>
+  %or = or <2 x i64> %shuf1, %shuf2
+  ret <2 x i64> %or
+}
+; CHECK-LABEL: test16
+; CHECK-NOT: pslldq
+; CHECK-NOT: por
+; CHECK: punpcklqdq
+; CHECK: ret
+
+
+; Verify that the dag-combiner does not fold a OR of two shuffles into a single
+; shuffle instruction when the shuffle indexes are not compatible.
+
+define <4 x i32> @test17(<4 x i32> %a, <4 x i32> %b) {
+  %shuf1 = shufflevector <4 x i32> %a, <4 x i32> zeroinitializer, <4 x i32><i32 4, i32 0, i32 4, i32 2>
+  %shuf2 = shufflevector <4 x i32> %b, <4 x i32> zeroinitializer, <4 x i32><i32 0, i32 1, i32 4, i32 4>
+  %or = or <4 x i32> %shuf1, %shuf2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test17
+; CHECK: por
+; CHECK-NEXT: ret
+
+
+define <4 x i32> @test18(<4 x i32> %a, <4 x i32> %b) {
+  %shuf1 = shufflevector <4 x i32> %a, <4 x i32> zeroinitializer, <4 x i32><i32 4, i32 0, i32 4, i32 4>
+  %shuf2 = shufflevector <4 x i32> %b, <4 x i32> zeroinitializer, <4 x i32><i32 0, i32 4, i32 4, i32 4>
+  %or = or <4 x i32> %shuf1, %shuf2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test18
+; CHECK: orps
+; CHECK: ret
+
+
+define <4 x i32> @test19(<4 x i32> %a, <4 x i32> %b) {
+  %shuf1 = shufflevector <4 x i32> %a, <4 x i32> zeroinitializer, <4 x i32><i32 4, i32 0, i32 4, i32 3>
+  %shuf2 = shufflevector <4 x i32> %b, <4 x i32> zeroinitializer, <4 x i32><i32 0, i32 4, i32 2, i32 2>
+  %or = or <4 x i32> %shuf1, %shuf2
+  ret <4 x i32> %or
+}
+; CHECK-LABEL: test19
+; CHECK: por
+; CHECK-NEXT: ret
+
+
+define <2 x i64> @test20(<2 x i64> %a, <2 x i64> %b) {
+  %shuf1 = shufflevector <2 x i64> %a, <2 x i64> zeroinitializer, <2 x i32><i32 0, i32 2>
+  %shuf2 = shufflevector <2 x i64> %b, <2 x i64> zeroinitializer, <2 x i32><i32 0, i32 2>
+  %or = or <2 x i64> %shuf1, %shuf2
+  ret <2 x i64> %or
+}
+; CHECK-LABEL: test20
+; CHECK-NOT: xorps
+; CHECK: orps
+; CHECK-NEXT: ret
+
+
+define <2 x i64> @test21(<2 x i64> %a, <2 x i64> %b) {
+  %shuf1 = shufflevector <2 x i64> %a, <2 x i64> zeroinitializer, <2 x i32><i32 2, i32 0>
+  %shuf2 = shufflevector <2 x i64> %b, <2 x i64> zeroinitializer, <2 x i32><i32 2, i32 0>
+  %or = or <2 x i64> %shuf1, %shuf2
+  ret <2 x i64> %or
+}
+; CHECK-LABEL: test21
+; CHECK: por
+; CHECK-NEXT: ret
+
+