[RISCV] Add isel optimization for (and (sra y, c2), c1) to recover regression from #101751. (#104114)

If c1 is a shifted mask with c3 leading zeros and c4 trailing zeros. If
c2 is greater than c3, we can use (srli (srai y, c2 - c3), c3 + c4)
followed by a SHXADD with c4 as the X amount.

Without Zba we can use (slli (srli (srai y, c2 - c3), c3 + c4), c4).
Alive2: https://alive2.llvm.org/ce/z/AwhheR

Author: topperc

llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp

@@ -1462,8 +1462,6 @@ void RISCVDAGToDAGISel::Select(SDNode *Node) {
 
     const uint64_t C1 = N1C->getZExtValue();
 
-    // Turn (and (sra x, c2), c1) -> (srli (srai x, c2-c3), c3) if c1 is a mask
-    // with c3 leading zeros and c2 is larger than c3.
     if (N0.getOpcode() == ISD::SRA && isa<ConstantSDNode>(N0.getOperand(1)) &&
         N0.hasOneUse()) {
       unsigned C2 = N0.getConstantOperandVal(1);
@@ -1477,6 +1475,8 @@ void RISCVDAGToDAGISel::Select(SDNode *Node) {
                   X.getOpcode() == ISD::SHL &&
                   isa<ConstantSDNode>(X.getOperand(1)) &&
                   X.getConstantOperandVal(1) == 32;
+      // Turn (and (sra x, c2), c1) -> (srli (srai x, c2-c3), c3) if c1 is a
+      // mask with c3 leading zeros and c2 is larger than c3.
       if (isMask_64(C1) && !Skip) {
         unsigned Leading = XLen - llvm::bit_width(C1);
         if (C2 > Leading) {
@@ -1490,6 +1490,27 @@ void RISCVDAGToDAGISel::Select(SDNode *Node) {
           return;
         }
       }
+
+      // Look for (and (sra y, c2), c1) where c1 is a shifted mask with c3
+      // leading zeros and c4 trailing zeros. If c2 is greater than c3, we can
+      // use (slli (srli (srai y, c2 - c3), c3 + c4), c4).
+      if (isShiftedMask_64(C1) && !Skip) {
+        unsigned Leading = XLen - llvm::bit_width(C1);
+        unsigned Trailing = llvm::countr_zero(C1);
+        if (C2 > Leading && Leading > 0 && Trailing > 0) {
+          SDNode *SRAI = CurDAG->getMachineNode(
+              RISCV::SRAI, DL, VT, N0.getOperand(0),
+              CurDAG->getTargetConstant(C2 - Leading, DL, VT));
+          SDNode *SRLI = CurDAG->getMachineNode(
+              RISCV::SRLI, DL, VT, SDValue(SRAI, 0),
+              CurDAG->getTargetConstant(Leading + Trailing, DL, VT));
+          SDNode *SLLI = CurDAG->getMachineNode(
+              RISCV::SLLI, DL, VT, SDValue(SRLI, 0),
+              CurDAG->getTargetConstant(Trailing, DL, VT));
+          ReplaceNode(Node, SLLI);
+          return;
+        }
+      }
     }
 
     // If C1 masks off the upper bits only (but can't be formed as an
@@ -3032,6 +3053,33 @@ bool RISCVDAGToDAGISel::selectSHXADDOp(SDValue N, unsigned ShAmt,
           return true;
         }
       }
+    } else if (N0.getOpcode() == ISD::SRA && N0.hasOneUse() &&
+               isa<ConstantSDNode>(N.getOperand(1))) {
+      uint64_t Mask = N.getConstantOperandVal(1);
+      unsigned C2 = N0.getConstantOperandVal(1);
+
+      // Look for (and (sra y, c2), c1) where c1 is a shifted mask with c3
+      // leading zeros and c4 trailing zeros. If c2 is greater than c3, we can
+      // use (srli (srai y, c2 - c3), c3 + c4) followed by a SHXADD with c4 as
+      // the X amount.
+      if (isShiftedMask_64(Mask)) {
+        unsigned XLen = Subtarget->getXLen();
+        unsigned Leading = XLen - llvm::bit_width(Mask);
+        unsigned Trailing = llvm::countr_zero(Mask);
+        if (C2 > Leading && Leading > 0 && Trailing == ShAmt) {
+          SDLoc DL(N);
+          EVT VT = N.getValueType();
+          Val = SDValue(CurDAG->getMachineNode(
+                            RISCV::SRAI, DL, VT, N0.getOperand(0),
+                            CurDAG->getTargetConstant(C2 - Leading, DL, VT)),
+                        0);
+          Val = SDValue(CurDAG->getMachineNode(
+                            RISCV::SRLI, DL, VT, Val,
+                            CurDAG->getTargetConstant(Leading + ShAmt, DL, VT)),
+                        0);
+          return true;
+        }
+      }
     }
   } else if (bool LeftShift = N.getOpcode() == ISD::SHL;
              (LeftShift || N.getOpcode() == ISD::SRL) &&

llvm/test/CodeGen/RISCV/rv64zba.ll

@@ -2988,3 +2988,69 @@ entry:
   %2 = and i64 %1, 34359738360
   ret i64 %2
 }
+
+define ptr @srai_srli_sh3add(ptr %0, i64 %1) nounwind {
+; RV64I-LABEL: srai_srli_sh3add:
+; RV64I:       # %bb.0: # %entry
+; RV64I-NEXT:    srai a1, a1, 32
+; RV64I-NEXT:    srli a1, a1, 6
+; RV64I-NEXT:    slli a1, a1, 3
+; RV64I-NEXT:    add a0, a0, a1
+; RV64I-NEXT:    ret
+;
+; RV64ZBA-LABEL: srai_srli_sh3add:
+; RV64ZBA:       # %bb.0: # %entry
+; RV64ZBA-NEXT:    srai a1, a1, 32
+; RV64ZBA-NEXT:    srli a1, a1, 6
+; RV64ZBA-NEXT:    sh3add a0, a1, a0
+; RV64ZBA-NEXT:    ret
+entry:
+  %2 = ashr i64 %1, 32
+  %3 = lshr i64 %2, 6
+  %4 = getelementptr i64, ptr %0, i64 %3
+  ret ptr %4
+}
+
+define ptr @srai_srli_slli(ptr %0, i64 %1) nounwind {
+; CHECK-LABEL: srai_srli_slli:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    srai a1, a1, 32
+; CHECK-NEXT:    srli a1, a1, 6
+; CHECK-NEXT:    slli a1, a1, 4
+; CHECK-NEXT:    add a0, a0, a1
+; CHECK-NEXT:    ret
+entry:
+  %2 = ashr i64 %1, 32
+  %3 = lshr i64 %2, 6
+  %4 = getelementptr i128, ptr %0, i64 %3
+  ret ptr %4
+}
+
+; Negative to make sure the peephole added for srai_srli_slli and
+; srai_srli_sh3add doesn't break this.
+define i64 @srai_andi(i64 %x) nounwind {
+; CHECK-LABEL: srai_andi:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    srai a0, a0, 8
+; CHECK-NEXT:    andi a0, a0, -8
+; CHECK-NEXT:    ret
+entry:
+  %y = ashr i64 %x, 8
+  %z = and i64 %y, -8
+  ret i64 %z
+}
+
+; Negative to make sure the peephole added for srai_srli_slli and
+; srai_srli_sh3add doesn't break this.
+define i64 @srai_lui_and(i64 %x) nounwind {
+; CHECK-LABEL: srai_lui_and:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    srai a0, a0, 8
+; CHECK-NEXT:    lui a1, 1048574
+; CHECK-NEXT:    and a0, a0, a1
+; CHECK-NEXT:    ret
+entry:
+  %y = ashr i64 %x, 8
+  %z = and i64 %y, -8192
+  ret i64 %z
+}