[LoongArch] Implement isLegalICmpImmediate

This causes a trivial improvement in the legalicmpimm.ll test case.

Signed-off-by: WANG Rui <[email protected]>

Reviewed By: SixWeining, xen0n

Differential Revision: https://reviews.llvm.org/D154811

Author: heiher

llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp

@@ -3247,6 +3247,10 @@ bool LoongArchTargetLowering::isLegalAddressingMode(const DataLayout &DL,
   return true;
 }
 
+bool LoongArchTargetLowering::isLegalICmpImmediate(int64_t Imm) const {
+  return isInt<12>(Imm);
+}
+
 bool LoongArchTargetLowering::isLegalAddImmediate(int64_t Imm) const {
   return isInt<12>(Imm);
 }

llvm/lib/Target/LoongArch/LoongArchISelLowering.h

@@ -202,6 +202,7 @@ class LoongArchTargetLowering : public TargetLowering {
                              unsigned AS,
                              Instruction *I = nullptr) const override;
 
+  bool isLegalICmpImmediate(int64_t Imm) const override;
   bool isLegalAddImmediate(int64_t Imm) const override;
 
   bool hasAndNotCompare(SDValue Y) const override;

llvm/test/CodeGen/LoongArch/legalicmpimm.ll

@@ -5,20 +5,15 @@
 define i32 @icmpimm(i32 %x) {
 ; LA32-LABEL: icmpimm:
 ; LA32:       # %bb.0:
-; LA32-NEXT:    lu12i.w $a1, -1
-; LA32-NEXT:    and $a0, $a0, $a1
-; LA32-NEXT:    lu12i.w $a1, 1
-; LA32-NEXT:    xor $a0, $a0, $a1
+; LA32-NEXT:    srli.w $a0, $a0, 12
+; LA32-NEXT:    addi.w $a0, $a0, -1
 ; LA32-NEXT:    sltui $a0, $a0, 1
 ; LA32-NEXT:    ret
 ;
 ; LA64-LABEL: icmpimm:
 ; LA64:       # %bb.0:
-; LA64-NEXT:    lu12i.w $a1, -1
-; LA64-NEXT:    lu32i.d $a1, 0
-; LA64-NEXT:    and $a0, $a0, $a1
-; LA64-NEXT:    lu12i.w $a1, 1
-; LA64-NEXT:    xor $a0, $a0, $a1
+; LA64-NEXT:    bstrpick.d $a0, $a0, 31, 12
+; LA64-NEXT:    addi.d $a0, $a0, -1
 ; LA64-NEXT:    sltui $a0, $a0, 1
 ; LA64-NEXT:    ret
   %1 = and i32 %x, -4096