[InstCombine] Fold icmp spred (X *nsw Z), (Y *nsw Z) i-> icmp pred Z, 0 if scmp(X, Y) is known

Author: dtcxzyw

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -5337,6 +5337,15 @@ Instruction *InstCombinerImpl::foldICmpBinOp(ICmpInst &I,
             return new ICmpInst(Pred, X, Y);
           if (ZKnown.isNegative())
             return new ICmpInst(ICmpInst::getSwappedPredicate(Pred), X, Y);
+          Value *LessThan = simplifyICmpInst(ICmpInst::ICMP_SLT, X, Y,
+                                             SQ.getWithInstruction(&I));
+          if (LessThan && match(LessThan, m_One()))
+            return new ICmpInst(ICmpInst::getSwappedPredicate(Pred), Z,
+                                Constant::getNullValue(Z->getType()));
+          Value *GreaterThan = simplifyICmpInst(ICmpInst::ICMP_SGT, X, Y,
+                                                SQ.getWithInstruction(&I));
+          if (GreaterThan && match(GreaterThan, m_One()))
+            return new ICmpInst(Pred, Z, Constant::getNullValue(Z->getType()));
         }
       } else {
         bool NonZero;

llvm/test/Transforms/InstCombine/icmp-mul.ll

@@ -1468,10 +1468,7 @@ entry:
 define i1 @test_icmp_slt_mul_known_sgt(i64 %x, i64 %z) {
 ; CHECK-LABEL: @test_icmp_slt_mul_known_sgt(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[Y:%.*]] = add nsw i64 [[X:%.*]], 1
-; CHECK-NEXT:    [[MUL1:%.*]] = mul nsw i64 [[X]], [[Z:%.*]]
-; CHECK-NEXT:    [[MUL2:%.*]] = mul nsw i64 [[Y]], [[Z]]
-; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i64 [[MUL1]], [[MUL2]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i64 [[Z:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
 entry:
@@ -1485,10 +1482,7 @@ entry:
 define i1 @test_icmp_sle_mul_known_sgt(i64 %x, i64 %z) {
 ; CHECK-LABEL: @test_icmp_sle_mul_known_sgt(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[Y:%.*]] = add nsw i64 [[X:%.*]], 1
-; CHECK-NEXT:    [[MUL1:%.*]] = mul nsw i64 [[X]], [[Z:%.*]]
-; CHECK-NEXT:    [[MUL2:%.*]] = mul nsw i64 [[Y]], [[Z]]
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sle i64 [[MUL1]], [[MUL2]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i64 [[Z:%.*]], -1
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
 entry:
@@ -1502,10 +1496,7 @@ entry:
 define i1 @test_icmp_mul_known_slt(i64 %x, i64 %z) {
 ; CHECK-LABEL: @test_icmp_mul_known_slt(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[Y:%.*]] = add nsw i64 [[X:%.*]], 1
-; CHECK-NEXT:    [[MUL1:%.*]] = mul nsw i64 [[X]], [[Z:%.*]]
-; CHECK-NEXT:    [[MUL2:%.*]] = mul nsw i64 [[Y]], [[Z]]
-; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i64 [[MUL2]], [[MUL1]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i64 [[Z:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
 entry:
@@ -1519,10 +1510,7 @@ entry:
 define i1 @test_icmp_slt_mul_known_sgt_commuted1(i64 %x, i64 %z) {
 ; CHECK-LABEL: @test_icmp_slt_mul_known_sgt_commuted1(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[Y:%.*]] = add nsw i64 [[X:%.*]], 1
-; CHECK-NEXT:    [[MUL1:%.*]] = mul nsw i64 [[Z:%.*]], [[X]]
-; CHECK-NEXT:    [[MUL2:%.*]] = mul nsw i64 [[Y]], [[Z]]
-; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i64 [[MUL1]], [[MUL2]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i64 [[Z:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
 entry:
@@ -1536,10 +1524,7 @@ entry:
 define i1 @test_icmp_slt_mul_known_sgt_commuted2(i64 %x, i64 %z) {
 ; CHECK-LABEL: @test_icmp_slt_mul_known_sgt_commuted2(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[Y:%.*]] = add nsw i64 [[X:%.*]], 1
-; CHECK-NEXT:    [[MUL1:%.*]] = mul nsw i64 [[X]], [[Z:%.*]]
-; CHECK-NEXT:    [[MUL2:%.*]] = mul nsw i64 [[Z]], [[Y]]
-; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i64 [[MUL1]], [[MUL2]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i64 [[Z:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
 entry: