[llvm] 3101601 - [PowerPC] Exploit vabsd on P9

[via llvm-commits]

Author: Li Rong Yi
Date: 2020-06-01T02:30:27Z
New Revision: 3101601b54fbb8062c179e804974b9fb4e2b7c19

URL: https://github.com/llvm/llvm-project/commit/3101601b54fbb8062c179e804974b9fb4e2b7c19
DIFF: https://github.com/llvm/llvm-project/commit/3101601b54fbb8062c179e804974b9fb4e2b7c19.diff

LOG: [PowerPC] Exploit vabsd on P9

Summary: Exploit vabsd* for for absolute difference of vectors on P9,
for example:
void foo (char *restrict p, char *restrict q, char *restrict t)
{
  for (int i = 0; i < 16; i++)
     t[i] = abs (p[i] - q[i]);
}
this case should be matched to the HW instruction vabsdub.

Reviewed By: steven.zhang

Differential Revision: https://reviews.llvm.org/D80271

Added: 
    

Modified: 
    llvm/lib/Target/PowerPC/PPCISelLowering.cpp
    llvm/test/CodeGen/PowerPC/vec_absd.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 7e0cbbff2515..0ede11ee285a 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -16053,6 +16053,24 @@ SDValue PPCTargetLowering::combineTRUNCATE(SDNode *N,
   SDLoc dl(N);
   SDValue Op0 = N->getOperand(0);
 
+  // fold (truncate (abs (sub (zext a), (zext b)))) -> (vabsd a, b)
+  if (Subtarget.hasP9Altivec() && Op0.getOpcode() == ISD::ABS) {
+    EVT VT = N->getValueType(0);
+    if (VT != MVT::v4i32 && VT != MVT::v8i16 && VT != MVT::v16i8)
+      return SDValue();
+    SDValue Sub = Op0.getOperand(0);
+    if (Sub.getOpcode() == ISD::SUB) {
+      SDValue SubOp0 = Sub.getOperand(0);
+      SDValue SubOp1 = Sub.getOperand(1);
+      if ((SubOp0.getOpcode() == ISD::ZERO_EXTEND) &&
+          (SubOp1.getOpcode() == ISD::ZERO_EXTEND)) {
+        return DCI.DAG.getNode(PPCISD::VABSD, dl, VT, SubOp0.getOperand(0),
+                               SubOp1.getOperand(0),
+                               DCI.DAG.getTargetConstant(0, dl, MVT::i32));
+      }
+    }
+  }
+
   // Looking for a truncate of i128 to i64.
   if (Op0.getValueType() != MVT::i128 || N->getValueType(0) != MVT::i64)
     return SDValue();

diff  --git a/llvm/test/CodeGen/PowerPC/vec_absd.ll b/llvm/test/CodeGen/PowerPC/vec_absd.ll
index 268587bb2eaf..1ae3ee5d2590 100644
--- a/llvm/test/CodeGen/PowerPC/vec_absd.ll
+++ b/llvm/test/CodeGen/PowerPC/vec_absd.ll
@@ -38,3 +38,45 @@ entry:
 ; CHECK: vabsduw 2, 2, 3
 ; CHECK: blr
 }
+
+define <16 x i8> @test_vabsdub(<16 x i8> %0, <16 x i8> %1) {
+entry:
+  %2 = zext <16 x i8> %0 to <16 x i32>
+  %3 = zext <16 x i8> %1 to <16 x i32>
+  %4 = sub nsw <16 x i32> %2, %3
+  %5 = icmp slt <16 x i32> %4, zeroinitializer
+  %6 = sub nsw <16 x i32> zeroinitializer, %4
+  %7 = select <16 x i1> %5, <16 x i32> %6, <16 x i32> %4
+  %8 = trunc <16 x i32> %7 to <16 x i8>
+  ret <16 x i8> %8
+; CHECK-LABEL: @test_vabsdub
+; CHECK: vabsdub 2, 2, 3
+; CHECK: blr
+}
+
+define <8 x i16> @test_vabsduh(<8 x i16> %0, <8 x i16> %1) {
+entry:
+  %2 = zext <8 x i16> %0 to <8 x i32>
+  %3 = zext <8 x i16> %1 to <8 x i32>
+  %4 = sub nsw <8 x i32> %2, %3
+  %5 = icmp slt <8 x i32> %4, zeroinitializer
+  %6 = sub nsw <8 x i32> zeroinitializer, %4
+  %7 = select <8 x i1> %5, <8 x i32> %6, <8 x i32> %4
+  %8 = trunc <8 x i32> %7 to <8 x i16>
+  ret <8 x i16> %8
+; CHECK-LABEL: @test_vabsduh
+; CHECK: vabsduh 2, 2, 3
+; CHECK: blr
+}
+
+define <4 x i32> @test_vabsduw(<4 x i32> %0, <4 x i32> %1) {
+entry:
+  %2 = sub nsw <4 x i32> %0, %1
+  %3 = icmp slt <4 x i32> %2, zeroinitializer
+  %4 = sub nsw <4 x i32> zeroinitializer, %2
+  %5 = select <4 x i1> %3, <4 x i32> %4, <4 x i32> %2
+  ret <4 x i32> %5
+; CHECK-LABEL: @test_vabsduw
+; CHECK: vabsduw 2, 2, 3
+; CHECK: blr
+}