[X86] In combineLoopSADPattern, pad result with zeros and use full size add instead...

In some cases the result psadbw is smaller than the type of the add that started the match. Currently in these cases we are using a smaller add and inserting the result.

If we instead combine the psadbw with zeros and use the full size add we can take advantage of implicit zeroing we get if we emit a narrower move before the add.

In a future patch, I want to make isel aware that the psadbw itself already zeroed the upper bits and remove the move entirely.

Differential Revision: https://reviews.llvm.org/D37453

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@314331 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 0852765333d465471d7ccd47e52e5d69a3b13166..1cd3af98dc98fff7d16c704654547b88f14385e5 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -35536,16 +35536,13 @@ static SDValue combineLoopSADPattern(SDNode *N, SelectionDAG &DAG,
     Sad = DAG.getNode(ISD::TRUNCATE, DL, VT, Sad);
 
   if (VT.getSizeInBits() > ResVT.getSizeInBits()) {
-    // Update part of elements of the reduction vector. This is done by first
-    // extracting a sub-vector from it, updating this sub-vector, and inserting
-    // it back.
-    SDValue SubPhi = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, ResVT, Phi,
-                                 DAG.getIntPtrConstant(0, DL));
-    SDValue Res = DAG.getNode(ISD::ADD, DL, ResVT, Sad, SubPhi);
-    return DAG.getNode(ISD::INSERT_SUBVECTOR, DL, VT, Phi, Res,
-                       DAG.getIntPtrConstant(0, DL));
-  } else
-    return DAG.getNode(ISD::ADD, DL, VT, Sad, Phi);
+    // Fill the upper elements with zero to match the add width.
+    SDValue Zero = DAG.getConstant(0, DL, VT);
+    Sad = DAG.getNode(ISD::INSERT_SUBVECTOR, DL, VT, Zero, Sad,
+                      DAG.getIntPtrConstant(0, DL));
+  }
+
+  return DAG.getNode(ISD::ADD, DL, VT, Sad, Phi);
 }
 
 /// Convert vector increment or decrement to sub/add with an all-ones constant:

diff --git a/test/CodeGen/X86/sad.ll b/test/CodeGen/X86/sad.ll
index 78e232917565805659cf404de6b279f930c7b02f..e8a55215dc8d5a3c6edf2fadefbf2d09173c1cd4 100644 (file)
--- a/test/CodeGen/X86/sad.ll
+++ b/test/CodeGen/X86/sad.ll
@@ -43,8 +43,8 @@ define i32 @sad_16i8() nounwind {
 ; AVX2-NEXT:    # =>This Inner Loop Header: Depth=1
 ; AVX2-NEXT:    vmovdqu a+1024(%rax), %xmm2
 ; AVX2-NEXT:    vpsadbw b+1024(%rax), %xmm2, %xmm2
-; AVX2-NEXT:    vpaddd %xmm1, %xmm2, %xmm2
-; AVX2-NEXT:    vpblendd {{.*#+}} ymm1 = ymm2[0,1,2,3],ymm1[4,5,6,7]
+; AVX2-NEXT:    vmovdqa %xmm2, %xmm2
+; AVX2-NEXT:    vpaddd %ymm1, %ymm2, %ymm1
 ; AVX2-NEXT:    addq $4, %rax
 ; AVX2-NEXT:    jne .LBB0_1
 ; AVX2-NEXT:  # BB#2: # %middle.block
@@ -67,8 +67,8 @@ define i32 @sad_16i8() nounwind {
 ; AVX512F-NEXT:    # =>This Inner Loop Header: Depth=1
 ; AVX512F-NEXT:    vmovdqu a+1024(%rax), %xmm1
 ; AVX512F-NEXT:    vpsadbw b+1024(%rax), %xmm1, %xmm1
-; AVX512F-NEXT:    vpaddd %xmm0, %xmm1, %xmm1
-; AVX512F-NEXT:    vinserti32x4 $0, %xmm1, %zmm0, %zmm0
+; AVX512F-NEXT:    vmovdqa %xmm1, %xmm1
+; AVX512F-NEXT:    vpaddd %zmm0, %zmm1, %zmm0
 ; AVX512F-NEXT:    addq $4, %rax
 ; AVX512F-NEXT:    jne .LBB0_1
 ; AVX512F-NEXT:  # BB#2: # %middle.block
@@ -93,8 +93,8 @@ define i32 @sad_16i8() nounwind {
 ; AVX512BW-NEXT:    # =>This Inner Loop Header: Depth=1
 ; AVX512BW-NEXT:    vmovdqu a+1024(%rax), %xmm1
 ; AVX512BW-NEXT:    vpsadbw b+1024(%rax), %xmm1, %xmm1
-; AVX512BW-NEXT:    vpaddd %xmm0, %xmm1, %xmm1
-; AVX512BW-NEXT:    vinserti32x4 $0, %xmm1, %zmm0, %zmm0
+; AVX512BW-NEXT:    vmovdqa %xmm1, %xmm1
+; AVX512BW-NEXT:    vpaddd %zmm0, %zmm1, %zmm0
 ; AVX512BW-NEXT:    addq $4, %rax
 ; AVX512BW-NEXT:    jne .LBB0_1
 ; AVX512BW-NEXT:  # BB#2: # %middle.block
@@ -315,8 +315,8 @@ define i32 @sad_32i8() nounwind {
 ; AVX512F-NEXT:    # =>This Inner Loop Header: Depth=1
 ; AVX512F-NEXT:    vmovdqa a+1024(%rax), %ymm2
 ; AVX512F-NEXT:    vpsadbw b+1024(%rax), %ymm2, %ymm2
-; AVX512F-NEXT:    vpaddd %ymm1, %ymm2, %ymm2
-; AVX512F-NEXT:    vinserti64x4 $0, %ymm2, %zmm1, %zmm1
+; AVX512F-NEXT:    vmovdqa %ymm2, %ymm2
+; AVX512F-NEXT:    vpaddd %zmm1, %zmm2, %zmm1
 ; AVX512F-NEXT:    addq $4, %rax
 ; AVX512F-NEXT:    jne .LBB1_1
 ; AVX512F-NEXT:  # BB#2: # %middle.block
@@ -343,8 +343,8 @@ define i32 @sad_32i8() nounwind {
 ; AVX512BW-NEXT:    # =>This Inner Loop Header: Depth=1
 ; AVX512BW-NEXT:    vmovdqa a+1024(%rax), %ymm2
 ; AVX512BW-NEXT:    vpsadbw b+1024(%rax), %ymm2, %ymm2
-; AVX512BW-NEXT:    vpaddd %ymm1, %ymm2, %ymm2
-; AVX512BW-NEXT:    vinserti64x4 $0, %ymm2, %zmm1, %zmm1
+; AVX512BW-NEXT:    vmovdqa %ymm2, %ymm2
+; AVX512BW-NEXT:    vpaddd %zmm1, %zmm2, %zmm1
 ; AVX512BW-NEXT:    addq $4, %rax
 ; AVX512BW-NEXT:    jne .LBB1_1
 ; AVX512BW-NEXT:  # BB#2: # %middle.block