[RISCV] Add ORC_B to SimplifyDemandedBitsForTargetNode. (#141975)

Author: topperc

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -20591,7 +20591,8 @@ void RISCVTargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
     // control value of 7 is equivalent to brev8 and orc.b.
     Known = DAG.computeKnownBits(Op.getOperand(0), Depth + 1);
     bool IsGORC = Op.getOpcode() == RISCVISD::ORC_B;
-    // To compute zeros, we need to invert the value and invert it back after.
+    // To compute zeros for ORC_B, we need to invert the value and invert it
+    // back after. This inverting is harmless for BREV8.
     Known.Zero =
         ~computeGREVOrGORC(~Known.Zero.getZExtValue(), 7, IsGORC);
     Known.One = computeGREVOrGORC(Known.One.getZExtValue(), 7, IsGORC);
@@ -20741,19 +20742,24 @@ bool RISCVTargetLowering::SimplifyDemandedBitsForTargetNode(
   unsigned BitWidth = OriginalDemandedBits.getBitWidth();
 
   switch (Op.getOpcode()) {
-  case RISCVISD::BREV8: {
+  case RISCVISD::BREV8:
+  case RISCVISD::ORC_B: {
     KnownBits Known2;
+    bool IsGORC = Op.getOpcode() == RISCVISD::ORC_B;
+    // For BREV8, we need to do BREV8 on the demanded bits.
+    // For ORC_B, any bit in the output demandeds all bits from the same byte.
+    // So we need to do ORC_B on the demanded bits.
     APInt DemandedBits =
         APInt(BitWidth, computeGREVOrGORC(OriginalDemandedBits.getZExtValue(),
-                                          7, /*IsGORC=*/false));
+                                          7, IsGORC));
     if (SimplifyDemandedBits(Op.getOperand(0), DemandedBits,
                              OriginalDemandedElts, Known2, TLO, Depth + 1))
       return true;
 
-    Known.Zero =
-        computeGREVOrGORC(Known2.Zero.getZExtValue(), 7, /*IsGORC=*/false);
-    Known.One =
-        computeGREVOrGORC(Known2.One.getZExtValue(), 7, /*IsGORC=*/false);
+    // To compute zeros for ORC_B, we need to invert the value and invert it
+    // back after. This inverting is harmless for BREV8.
+    Known.Zero = ~computeGREVOrGORC(~Known2.Zero.getZExtValue(), 7, IsGORC);
+    Known.One = computeGREVOrGORC(Known2.One.getZExtValue(), 7, IsGORC);
     return false;
   }
   }

llvm/test/CodeGen/RISCV/rv32zbb-intrinsic.ll

@@ -13,16 +13,17 @@ define i32 @orcb(i32 %a) nounwind {
   ret i32 %tmp
 }
 
-; Second and+or are redundant with the first, make sure we remove it.
+; Second and+or are redundant with the first, make sure we remove one of the
+; ands and one of the ors.
 define i32 @orcb_knownbits(i32 %a) nounwind {
 ; RV32ZBB-LABEL: orcb_knownbits:
 ; RV32ZBB:       # %bb.0:
 ; RV32ZBB-NEXT:    lui a1, 1044480
 ; RV32ZBB-NEXT:    and a0, a0, a1
-; RV32ZBB-NEXT:    lui a1, 2048
-; RV32ZBB-NEXT:    addi a1, a1, 1
-; RV32ZBB-NEXT:    or a0, a0, a1
+; RV32ZBB-NEXT:    lui a1, 4080
 ; RV32ZBB-NEXT:    orc.b a0, a0
+; RV32ZBB-NEXT:    addi a1, a1, 255
+; RV32ZBB-NEXT:    or a0, a0, a1
 ; RV32ZBB-NEXT:    ret
   %tmp = and i32 %a, 4278190080 ; 0xFF000000
   %tmp2 = or i32 %tmp, 8388609 ; 0x800001

llvm/test/CodeGen/RISCV/rv64zbb-intrinsic.ll

@@ -29,10 +29,10 @@ define signext i32 @orcb32_knownbits(i32 signext %a) nounwind {
 ; RV64ZBB:       # %bb.0:
 ; RV64ZBB-NEXT:    lui a1, 1044480
 ; RV64ZBB-NEXT:    and a0, a0, a1
-; RV64ZBB-NEXT:    lui a1, 2048
-; RV64ZBB-NEXT:    addi a1, a1, 1
-; RV64ZBB-NEXT:    or a0, a0, a1
+; RV64ZBB-NEXT:    lui a1, 4080
 ; RV64ZBB-NEXT:    orc.b a0, a0
+; RV64ZBB-NEXT:    addi a1, a1, 255
+; RV64ZBB-NEXT:    or a0, a0, a1
 ; RV64ZBB-NEXT:    sext.w a0, a0
 ; RV64ZBB-NEXT:    ret
   %tmp = and i32 %a, 4278190080 ; 0xFF000000
@@ -54,19 +54,20 @@ define i64 @orcb64(i64 %a) nounwind {
   ret i64 %tmp
 }
 
-; Second and+or is redundant with the first, make sure we remove them.
+; Second and+or is redundant with the first, make sure we remove one of the ands
+; and one of the ors.
 define i64 @orcb64_knownbits(i64 %a) nounwind {
 ; RV64ZBB-LABEL: orcb64_knownbits:
 ; RV64ZBB:       # %bb.0:
 ; RV64ZBB-NEXT:    lui a1, 65535
-; RV64ZBB-NEXT:    lui a2, 256
+; RV64ZBB-NEXT:    lui a2, 4080
 ; RV64ZBB-NEXT:    slli a1, a1, 12
-; RV64ZBB-NEXT:    addiw a2, a2, 8
+; RV64ZBB-NEXT:    addiw a2, a2, 255
 ; RV64ZBB-NEXT:    and a0, a0, a1
-; RV64ZBB-NEXT:    slli a1, a2, 42
+; RV64ZBB-NEXT:    slli a1, a2, 40
+; RV64ZBB-NEXT:    orc.b a0, a0
 ; RV64ZBB-NEXT:    add a1, a2, a1
 ; RV64ZBB-NEXT:    or a0, a0, a1
-; RV64ZBB-NEXT:    orc.b a0, a0
 ; RV64ZBB-NEXT:    ret
   %tmp = and i64 %a, 1099494850560 ; 0x000000ffff000000
   %tmp2 = or i64 %tmp, 4611721202800525320 ; 0x4000200000100008