[AArch64][GlobalISel] Combine MUL(AND(LSHR(X, 15), 0x10001), 0xffff) to CMLTz (#92915)

This patch mirrors the following SelectionDAG patch for GlobalISel:
https://reviews.llvm.org/D130874

Author: ChuongGoh-arm

llvm/lib/Target/AArch64/AArch64Combine.td

@@ -265,6 +265,14 @@ def or_to_bsp: GICombineRule <
   (apply [{ applyOrToBSP(*${root}, MRI, B, ${matchinfo}); }])
 >;
 
+// Combines Mul(And(Srl(X, 15), 0x10001), 0xffff) into CMLTz
+def combine_mul_cmlt : GICombineRule<
+  (defs root:$root, register_matchinfo:$matchinfo),
+  (match (wip_match_opcode G_MUL):$root,
+        [{ return matchCombineMulCMLT(*${root}, MRI, ${matchinfo}); }]),
+  (apply [{ applyCombineMulCMLT(*${root}, MRI, B, ${matchinfo}); }])
+>;
+
 // Post-legalization combines which should happen at all optimization levels.
 // (E.g. ones that facilitate matching for the selector) For example, matching
 // pseudos.
@@ -296,5 +304,6 @@ def AArch64PostLegalizerCombiner
                         split_store_zero_128, undef_combines,
                         select_to_minmax, or_to_bsp, combine_concat_vector,
                         commute_constant_to_rhs,
-                        push_freeze_to_prevent_poison_from_propagating]> {
+                        push_freeze_to_prevent_poison_from_propagating,
+                        combine_mul_cmlt]> {
 }

llvm/lib/Target/AArch64/GISel/AArch64PostLegalizerCombiner.cpp

@@ -381,6 +381,61 @@ void applyOrToBSP(MachineInstr &MI, MachineRegisterInfo &MRI,
   MI.eraseFromParent();
 }
 
+// Combines Mul(And(Srl(X, 15), 0x10001), 0xffff) into CMLTz
+bool matchCombineMulCMLT(MachineInstr &MI, MachineRegisterInfo &MRI,
+                         Register &SrcReg) {
+  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
+
+  if (DstTy != LLT::fixed_vector(2, 64) && DstTy != LLT::fixed_vector(2, 32) &&
+      DstTy != LLT::fixed_vector(4, 32) && DstTy != LLT::fixed_vector(4, 16) &&
+      DstTy != LLT::fixed_vector(8, 16))
+    return false;
+
+  auto AndMI = getDefIgnoringCopies(MI.getOperand(1).getReg(), MRI);
+  if (AndMI->getOpcode() != TargetOpcode::G_AND)
+    return false;
+  auto LShrMI = getDefIgnoringCopies(AndMI->getOperand(1).getReg(), MRI);
+  if (LShrMI->getOpcode() != TargetOpcode::G_LSHR)
+    return false;
+
+  // Check the constant splat values
+  auto V1 = isConstantOrConstantSplatVector(
+      *MRI.getVRegDef(MI.getOperand(2).getReg()), MRI);
+  auto V2 = isConstantOrConstantSplatVector(
+      *MRI.getVRegDef(AndMI->getOperand(2).getReg()), MRI);
+  auto V3 = isConstantOrConstantSplatVector(
+      *MRI.getVRegDef(LShrMI->getOperand(2).getReg()), MRI);
+  if (!V1.has_value() || !V2.has_value() || !V3.has_value())
+    return false;
+  unsigned HalfSize = DstTy.getScalarSizeInBits() / 2;
+  if (!V1.value().isMask(HalfSize) || V2.value() != (1ULL | 1ULL << HalfSize) ||
+      V3 != (HalfSize - 1))
+    return false;
+
+  SrcReg = LShrMI->getOperand(1).getReg();
+
+  return true;
+}
+
+void applyCombineMulCMLT(MachineInstr &MI, MachineRegisterInfo &MRI,
+                         MachineIRBuilder &B, Register &SrcReg) {
+  Register DstReg = MI.getOperand(0).getReg();
+  LLT DstTy = MRI.getType(DstReg);
+  LLT HalfTy =
+      DstTy.changeElementCount(DstTy.getElementCount().multiplyCoefficientBy(2))
+          .changeElementSize(DstTy.getScalarSizeInBits() / 2);
+
+  Register ZeroVec = B.buildConstant(HalfTy, 0).getReg(0);
+  Register CastReg =
+      B.buildInstr(TargetOpcode::G_BITCAST, {HalfTy}, {SrcReg}).getReg(0);
+  Register CMLTReg =
+      B.buildICmp(CmpInst::Predicate::ICMP_SLT, HalfTy, CastReg, ZeroVec)
+          .getReg(0);
+
+  B.buildInstr(TargetOpcode::G_BITCAST, {DstReg}, {CMLTReg}).getReg(0);
+  MI.eraseFromParent();
+}
+
 class AArch64PostLegalizerCombinerImpl : public Combiner {
 protected:
   // TODO: Make CombinerHelper methods const.

llvm/test/CodeGen/AArch64/mulcmle.ll

@@ -24,130 +24,66 @@ define <1 x i64> @v1i64(<1 x i64> %a) {
 }
 
 define <2 x i64> @v2i64(<2 x i64> %a) {
-; CHECK-SD-LABEL: v2i64:
-; CHECK-SD:       // %bb.0:
-; CHECK-SD-NEXT:    cmlt v0.4s, v0.4s, #0
-; CHECK-SD-NEXT:    ret
-;
-; CHECK-GI-LABEL: v2i64:
-; CHECK-GI:       // %bb.0:
-; CHECK-GI-NEXT:    movi v1.4s, #1
-; CHECK-GI-NEXT:    ushr v0.2d, v0.2d, #31
-; CHECK-GI-NEXT:    movi v2.2d, #0x000000ffffffff
-; CHECK-GI-NEXT:    and v0.16b, v0.16b, v1.16b
-; CHECK-GI-NEXT:    fmov x11, d2
-; CHECK-GI-NEXT:    mov x9, v2.d[1]
-; CHECK-GI-NEXT:    fmov x10, d0
-; CHECK-GI-NEXT:    mov x8, v0.d[1]
-; CHECK-GI-NEXT:    mul x10, x10, x11
-; CHECK-GI-NEXT:    mul x8, x8, x9
-; CHECK-GI-NEXT:    fmov d0, x10
-; CHECK-GI-NEXT:    mov v0.d[1], x8
-; CHECK-GI-NEXT:    ret
+; CHECK-LABEL: v2i64:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmlt v0.4s, v0.4s, #0
+; CHECK-NEXT:    ret
   %b = lshr <2 x i64> %a, <i64 31, i64 31>
   %c = and <2 x i64> %b, <i64 4294967297, i64 4294967297>
   %d = mul nuw <2 x i64> %c, <i64 4294967295, i64 4294967295>
   ret <2 x i64> %d
 }
 
 define <2 x i32> @v2i32(<2 x i32> %a) {
-; CHECK-SD-LABEL: v2i32:
-; CHECK-SD:       // %bb.0:
-; CHECK-SD-NEXT:    cmlt v0.4h, v0.4h, #0
-; CHECK-SD-NEXT:    ret
-;
-; CHECK-GI-LABEL: v2i32:
-; CHECK-GI:       // %bb.0:
-; CHECK-GI-NEXT:    movi v1.4h, #1
-; CHECK-GI-NEXT:    ushr v0.2s, v0.2s, #15
-; CHECK-GI-NEXT:    movi d2, #0x00ffff0000ffff
-; CHECK-GI-NEXT:    and v0.8b, v0.8b, v1.8b
-; CHECK-GI-NEXT:    mul v0.2s, v0.2s, v2.2s
-; CHECK-GI-NEXT:    ret
+; CHECK-LABEL: v2i32:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmlt v0.4h, v0.4h, #0
+; CHECK-NEXT:    ret
   %b = lshr <2 x i32> %a, <i32 15, i32 15>
   %c = and <2 x i32> %b, <i32 65537, i32 65537>
   %d = mul nuw <2 x i32> %c, <i32 65535, i32 65535>
   ret <2 x i32> %d
 }
 
 define <4 x i32> @v4i32(<4 x i32> %a) {
-; CHECK-SD-LABEL: v4i32:
-; CHECK-SD:       // %bb.0:
-; CHECK-SD-NEXT:    cmlt v0.8h, v0.8h, #0
-; CHECK-SD-NEXT:    ret
-;
-; CHECK-GI-LABEL: v4i32:
-; CHECK-GI:       // %bb.0:
-; CHECK-GI-NEXT:    movi v1.8h, #1
-; CHECK-GI-NEXT:    ushr v0.4s, v0.4s, #15
-; CHECK-GI-NEXT:    movi v2.2d, #0x00ffff0000ffff
-; CHECK-GI-NEXT:    and v0.16b, v0.16b, v1.16b
-; CHECK-GI-NEXT:    mul v0.4s, v0.4s, v2.4s
-; CHECK-GI-NEXT:    ret
+; CHECK-LABEL: v4i32:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmlt v0.8h, v0.8h, #0
+; CHECK-NEXT:    ret
   %b = lshr <4 x i32> %a, <i32 15, i32 15, i32 15, i32 15>
   %c = and <4 x i32> %b, <i32 65537, i32 65537, i32 65537, i32 65537>
   %d = mul nuw <4 x i32> %c, <i32 65535, i32 65535, i32 65535, i32 65535>
   ret <4 x i32> %d
 }
 
 define <8 x i32> @v8i32(<8 x i32> %a) {
-; CHECK-SD-LABEL: v8i32:
-; CHECK-SD:       // %bb.0:
-; CHECK-SD-NEXT:    cmlt v0.8h, v0.8h, #0
-; CHECK-SD-NEXT:    cmlt v1.8h, v1.8h, #0
-; CHECK-SD-NEXT:    ret
-;
-; CHECK-GI-LABEL: v8i32:
-; CHECK-GI:       // %bb.0:
-; CHECK-GI-NEXT:    movi v2.8h, #1
-; CHECK-GI-NEXT:    ushr v0.4s, v0.4s, #15
-; CHECK-GI-NEXT:    ushr v1.4s, v1.4s, #15
-; CHECK-GI-NEXT:    movi v3.2d, #0x00ffff0000ffff
-; CHECK-GI-NEXT:    and v0.16b, v0.16b, v2.16b
-; CHECK-GI-NEXT:    and v1.16b, v1.16b, v2.16b
-; CHECK-GI-NEXT:    mul v0.4s, v0.4s, v3.4s
-; CHECK-GI-NEXT:    mul v1.4s, v1.4s, v3.4s
-; CHECK-GI-NEXT:    ret
+; CHECK-LABEL: v8i32:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmlt v0.8h, v0.8h, #0
+; CHECK-NEXT:    cmlt v1.8h, v1.8h, #0
+; CHECK-NEXT:    ret
   %b = lshr <8 x i32> %a, <i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15>
   %c = and <8 x i32> %b, <i32 65537, i32 65537, i32 65537, i32 65537, i32 65537, i32 65537, i32 65537, i32 65537>
   %d = mul nuw <8 x i32> %c, <i32 65535, i32 65535, i32 65535, i32 65535, i32 65535, i32 65535, i32 65535, i32 65535>
   ret <8 x i32> %d
 }
 
 define <4 x i16> @v4i16(<4 x i16> %a) {
-; CHECK-SD-LABEL: v4i16:
-; CHECK-SD:       // %bb.0:
-; CHECK-SD-NEXT:    cmlt v0.8b, v0.8b, #0
-; CHECK-SD-NEXT:    ret
-;
-; CHECK-GI-LABEL: v4i16:
-; CHECK-GI:       // %bb.0:
-; CHECK-GI-NEXT:    movi v1.8b, #1
-; CHECK-GI-NEXT:    ushr v0.4h, v0.4h, #7
-; CHECK-GI-NEXT:    movi d2, #0xff00ff00ff00ff
-; CHECK-GI-NEXT:    and v0.8b, v0.8b, v1.8b
-; CHECK-GI-NEXT:    mul v0.4h, v0.4h, v2.4h
-; CHECK-GI-NEXT:    ret
+; CHECK-LABEL: v4i16:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmlt v0.8b, v0.8b, #0
+; CHECK-NEXT:    ret
   %b = lshr <4 x i16> %a, <i16 7, i16 7, i16 7, i16 7>
   %c = and <4 x i16> %b, <i16 257, i16 257, i16 257, i16 257>
   %d = mul nuw <4 x i16> %c, <i16 255, i16 255, i16 255, i16 255>
   ret <4 x i16> %d
 }
 
 define <8 x i16> @v8i16(<8 x i16> %a) {
-; CHECK-SD-LABEL: v8i16:
-; CHECK-SD:       // %bb.0:
-; CHECK-SD-NEXT:    cmlt v0.16b, v0.16b, #0
-; CHECK-SD-NEXT:    ret
-;
-; CHECK-GI-LABEL: v8i16:
-; CHECK-GI:       // %bb.0:
-; CHECK-GI-NEXT:    movi v1.16b, #1
-; CHECK-GI-NEXT:    ushr v0.8h, v0.8h, #7
-; CHECK-GI-NEXT:    movi v2.2d, #0xff00ff00ff00ff
-; CHECK-GI-NEXT:    and v0.16b, v0.16b, v1.16b
-; CHECK-GI-NEXT:    mul v0.8h, v0.8h, v2.8h
-; CHECK-GI-NEXT:    ret
+; CHECK-LABEL: v8i16:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmlt v0.16b, v0.16b, #0
+; CHECK-NEXT:    ret
   %b = lshr <8 x i16> %a, <i16 7, i16 7, i16 7, i16 7, i16 7, i16 7, i16 7, i16 7>
   %c = and <8 x i16> %b, <i16 257, i16 257, i16 257, i16 257, i16 257, i16 257, i16 257, i16 257>
   %d = mul nuw <8 x i16> %c, <i16 255, i16 255, i16 255, i16 255, i16 255, i16 255, i16 255, i16 255>