[InstSimplify] Simplify 'x u>= 1' to true when x is known non-zero

llvm/lib/Analysis/InstructionSimplify.cpp

@@ -2981,7 +2981,7 @@ static Value *simplifyICmpWithZero(CmpPredicate Pred, Value *LHS, Value *RHS,
 }
 
 static Value *simplifyICmpWithConstant(CmpPredicate Pred, Value *LHS,
-                                       Value *RHS, const InstrInfoQuery &IIQ) {
+                                       Value *RHS, const SimplifyQuery &Q) {
   Type *ITy = getCompareTy(RHS); // The return type.
 
   Value *X;
@@ -3007,7 +3007,7 @@ static Value *simplifyICmpWithConstant(CmpPredicate Pred, Value *LHS,
     return ConstantInt::getTrue(ITy);
 
   ConstantRange LHS_CR =
-      computeConstantRange(LHS, CmpInst::isSigned(Pred), IIQ.UseInstrInfo);
+      computeConstantRange(LHS, CmpInst::isSigned(Pred), Q.IIQ.UseInstrInfo);
   if (!LHS_CR.isFullSet()) {
     if (RHS_CR.contains(LHS_CR))
       return ConstantInt::getTrue(ITy);
@@ -3018,13 +3018,16 @@ static Value *simplifyICmpWithConstant(CmpPredicate Pred, Value *LHS,
   // (mul nuw/nsw X, MulC) != C --> true  (if C is not a multiple of MulC)
   // (mul nuw/nsw X, MulC) == C --> false (if C is not a multiple of MulC)
   const APInt *MulC;
-  if (IIQ.UseInstrInfo && ICmpInst::isEquality(Pred) &&
+  if (Q.IIQ.UseInstrInfo && ICmpInst::isEquality(Pred) &&
       ((match(LHS, m_NUWMul(m_Value(), m_APIntAllowPoison(MulC))) &&
         *MulC != 0 && C->urem(*MulC) != 0) ||
        (match(LHS, m_NSWMul(m_Value(), m_APIntAllowPoison(MulC))) &&
         *MulC != 0 && C->srem(*MulC) != 0)))
     return ConstantInt::get(ITy, Pred == ICmpInst::ICMP_NE);
 
+  if (Pred == ICmpInst::ICMP_UGE && C->isOne() && isKnownNonZero(LHS, Q))
+    return ConstantInt::getTrue(ITy);
+
   return nullptr;
 }
 
@@ -3776,7 +3779,7 @@ static Value *simplifyICmpInst(CmpPredicate Pred, Value *LHS, Value *RHS,
   if (Value *V = simplifyICmpWithZero(Pred, LHS, RHS, Q))
     return V;
 
-  if (Value *V = simplifyICmpWithConstant(Pred, LHS, RHS, Q.IIQ))
+  if (Value *V = simplifyICmpWithConstant(Pred, LHS, RHS, Q))
     return V;
 
   // If both operands have range metadata, use the metadata

llvm/test/Transforms/InstSimplify/umax-1.ll

@@ -0,0 +1,120 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
+
+define i32 @known_non_zero_by_or(i32 %x, i32 %y) {
+; CHECK-LABEL: define i32 @known_non_zero_by_or(
+; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[COND:%.*]] = icmp ne i32 [[X]], 0
+; CHECK-NEXT:    br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
+; CHECK:       [[IF_THEN]]:
+; CHECK-NEXT:    [[VAL:%.*]] = or i32 [[X]], [[Y]]
+; CHECK-NEXT:    ret i32 [[VAL]]
+; CHECK:       [[IF_ELSE]]:
+; CHECK-NEXT:    ret i32 0
+;
+  %cond = icmp ne i32 %x, 0
+  br i1 %cond, label %if.then, label %if.else
+
+if.then:
+  %val = or i32 %x, %y
+  %max = call i32 @llvm.umax.i32(i32 %val, i32 1)
+  ret i32 %max
+
+if.else:
+  ret i32 0
+}
+
+define i32 @known_non_zero_by_mul(i32 %x) {
+; CHECK-LABEL: define i32 @known_non_zero_by_mul(
+; CHECK-SAME: i32 [[X:%.*]]) {
+; CHECK-NEXT:    [[COND:%.*]] = icmp ne i32 [[X]], 0
+; CHECK-NEXT:    br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
+; CHECK:       [[IF_THEN]]:
+; CHECK-NEXT:    [[NONZERO1:%.*]] = mul nuw i32 [[X]], 3
+; CHECK-NEXT:    ret i32 [[NONZERO1]]
+; CHECK:       [[IF_ELSE]]:
+; CHECK-NEXT:    ret i32 0
+;
+  %cond = icmp ne i32 %x, 0
+  br i1 %cond, label %if.then, label %if.else
+
+if.then:
+  %nonzero = mul nuw i32 %x, 3
+  %max = call i32 @llvm.umax.i32(i32 %nonzero, i32 1)
+  ret i32 %max
+
+if.else:
+  ret i32 0
+}
+
+define i32 @known_non_zero_commute(i32 %x, i32 %y) {
+; CHECK-LABEL: define i32 @known_non_zero_commute(
+; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[COND:%.*]] = icmp ne i32 [[X]], 0
+; CHECK-NEXT:    br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
+; CHECK:       [[IF_THEN]]:
+; CHECK-NEXT:    [[VAL:%.*]] = or i32 [[X]], [[Y]]
+; CHECK-NEXT:    ret i32 [[VAL]]
+; CHECK:       [[IF_ELSE]]:
+; CHECK-NEXT:    ret i32 0
+;
+  %cond = icmp ne i32 %x, 0
+  br i1 %cond, label %if.then, label %if.else
+
+if.then:
+  %val = or i32 %x, %y
+  %max = call i32 @llvm.umax.i32(i32 1, i32 %val)
+  ret i32 %max
+
+if.else:
+  ret i32 0
+}
+
+; Negative
+define i32 @umax_ge_2(i32 %x, i32 %y) {
+; CHECK-LABEL: define i32 @umax_ge_2(
+; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[COND:%.*]] = icmp ne i32 [[X]], 0
+; CHECK-NEXT:    br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
+; CHECK:       [[IF_THEN]]:
+; CHECK-NEXT:    [[VAL:%.*]] = or i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[MAX:%.*]] = call i32 @llvm.umax.i32(i32 [[VAL]], i32 2)
+; CHECK-NEXT:    ret i32 [[MAX]]
+; CHECK:       [[IF_ELSE]]:
+; CHECK-NEXT:    ret i32 0
+;
+  %cond = icmp ne i32 %x, 0
+  br i1 %cond, label %if.then, label %if.else
+
+if.then:
+  %val = or i32 %x, %y
+  %max = call i32 @llvm.umax.i32(i32 %val, i32 2)
+  ret i32 %max
+
+if.else:
+  ret i32 0
+}
+
+define i32 @unknown_by_and(i32 %x, i32 %y) {
+; CHECK-LABEL: define i32 @unknown_by_and(
+; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[COND:%.*]] = icmp ne i32 [[X]], 0
+; CHECK-NEXT:    br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
+; CHECK:       [[IF_THEN]]:
+; CHECK-NEXT:    [[VAL:%.*]] = and i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[MAX:%.*]] = call i32 @llvm.umax.i32(i32 [[VAL]], i32 1)
+; CHECK-NEXT:    ret i32 [[MAX]]
+; CHECK:       [[IF_ELSE]]:
+; CHECK-NEXT:    ret i32 0
+;
+  %cond = icmp ne i32 %x, 0
+  br i1 %cond, label %if.then, label %if.else
+
+if.then:
+  %val = and i32 %x, %y
+  %max = call i32 @llvm.umax.i32(i32 %val, i32 1)
+  ret i32 %max
+
+if.else:
+  ret i32 0
+}