Add some transforms of the kind X-Y>X -> 0>Y which are valid when there is no

overflow.  These subsume some existing equality transforms, so zap those.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125843 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -2267,7 +2267,7 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
       return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()),
                           C == Op0 ? D : C);
 
-    // icmp (X+Y), (X+Z) -> icmp Y,Z for equalities or if there is no overflow.
+    // icmp (X+Y), (X+Z) -> icmp Y, Z for equalities or if there is no overflow.
     if (A && C && (A == C || A == D || B == C || B == D) &&
         NoOp0WrapProblem && NoOp1WrapProblem &&
         // Try not to increase register pressure.
@@ -2286,12 +2286,26 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
     if (BO1 && BO1->getOpcode() == Instruction::Sub)
       C = BO1->getOperand(0), D = BO1->getOperand(1);
 
-    // icmp (Y-X), (Z-X) -> icmp Y,Z for equalities or if there is no overflow.
+    // icmp (X-Y), X -> icmp 0, Y for equalities or if there is no overflow.
+    if (A == Op1 && NoOp0WrapProblem)
+      return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B);
+
+    // icmp X, (X-Y) -> icmp Y, 0 for equalities or if there is no overflow.
+    if (C == Op0 && NoOp1WrapProblem)
+      return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType()));
+
+    // icmp (Y-X), (Z-X) -> icmp Y, Z for equalities or if there is no overflow.
     if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem &&
         // Try not to increase register pressure.
         BO0->hasOneUse() && BO1->hasOneUse())
       return new ICmpInst(Pred, A, C);
 
+    // icmp (X-Y), (X-Z) -> icmp Z, Y for equalities or if there is no overflow.
+    if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem &&
+        // Try not to increase register pressure.
+        BO0->hasOneUse() && BO1->hasOneUse())
+      return new ICmpInst(Pred, D, B);
+
     if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() &&
         BO0->hasOneUse() && BO1->hasOneUse() &&
         BO0->getOperand(1) == BO1->getOperand(1)) {
@@ -2375,12 +2389,7 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
   
   if (I.isEquality()) {
     Value *A, *B, *C, *D;
-    
-    // -x == -y --> x == y
-    if (match(Op0, m_Neg(m_Value(A))) &&
-        match(Op1, m_Neg(m_Value(B))))
-      return new ICmpInst(I.getPredicate(), A, B);
-    
+
     if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
       if (A == Op1 || B == Op1) {    // (A^B) == A  ->  B == 0
         Value *OtherVal = A == Op1 ? B : A;
@@ -2415,16 +2424,6 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
                           Constant::getNullValue(A->getType()));
     }
 
-    // (A-B) == A  ->  B == 0
-    if (match(Op0, m_Sub(m_Specific(Op1), m_Value(B))))
-      return new ICmpInst(I.getPredicate(), B, 
-                          Constant::getNullValue(B->getType()));
-
-    // A == (A-B)  ->  B == 0
-    if (match(Op1, m_Sub(m_Specific(Op0), m_Value(B))))
-      return new ICmpInst(I.getPredicate(), B,
-                          Constant::getNullValue(B->getType()));
-
     // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
     if (Op0->hasOneUse() && Op1->hasOneUse() &&
         match(Op0, m_And(m_Value(A), m_Value(B))) && 

test/Transforms/InstCombine/icmp.ll

@@ -235,6 +235,7 @@ define i1 @test24(i64 %i) {
 }
 
 ; CHECK: @test25
+; X + Z > Y + Z -> X > Y if there is no overflow.
 ; CHECK: %c = icmp sgt i32 %x, %y
 ; CHECK: ret i1 %c
 define i1 @test25(i32 %x, i32 %y, i32 %z) {
@@ -245,11 +246,134 @@ define i1 @test25(i32 %x, i32 %y, i32 %z) {
 }
 
 ; CHECK: @test26
-; CHECK: %c = icmp sgt i32 %x, %y
+; X + Z > Y + Z -> X > Y if there is no overflow.
+; CHECK: %c = icmp ugt i32 %x, %y
 ; CHECK: ret i1 %c
 define i1 @test26(i32 %x, i32 %y, i32 %z) {
+  %lhs = add nuw i32 %x, %z
+  %rhs = add nuw i32 %y, %z
+  %c = icmp ugt i32 %lhs, %rhs
+  ret i1 %c
+}
+
+; CHECK: @test27
+; X - Z > Y - Z -> X > Y if there is no overflow.
+; CHECK: %c = icmp sgt i32 %x, %y
+; CHECK: ret i1 %c
+define i1 @test27(i32 %x, i32 %y, i32 %z) {
   %lhs = sub nsw i32 %x, %z
   %rhs = sub nsw i32 %y, %z
   %c = icmp sgt i32 %lhs, %rhs
   ret i1 %c
 }
+
+; CHECK: @test28
+; X - Z > Y - Z -> X > Y if there is no overflow.
+; CHECK: %c = icmp ugt i32 %x, %y
+; CHECK: ret i1 %c
+define i1 @test28(i32 %x, i32 %y, i32 %z) {
+  %lhs = sub nuw i32 %x, %z
+  %rhs = sub nuw i32 %y, %z
+  %c = icmp ugt i32 %lhs, %rhs
+  ret i1 %c
+}
+
+; CHECK: @test29
+; X + Y > X -> Y > 0 if there is no overflow.
+; CHECK: %c = icmp sgt i32 %y, 0
+; CHECK: ret i1 %c
+define i1 @test29(i32 %x, i32 %y) {
+  %lhs = add nsw i32 %x, %y
+  %c = icmp sgt i32 %lhs, %x
+  ret i1 %c
+}
+
+; CHECK: @test30
+; X + Y > X -> Y > 0 if there is no overflow.
+; CHECK: %c = icmp ne i32 %y, 0
+; CHECK: ret i1 %c
+define i1 @test30(i32 %x, i32 %y) {
+  %lhs = add nuw i32 %x, %y
+  %c = icmp ugt i32 %lhs, %x
+  ret i1 %c
+}
+
+; CHECK: @test31
+; X > X + Y -> 0 > Y if there is no overflow.
+; CHECK: %c = icmp slt i32 %y, 0
+; CHECK: ret i1 %c
+define i1 @test31(i32 %x, i32 %y) {
+  %rhs = add nsw i32 %x, %y
+  %c = icmp sgt i32 %x, %rhs
+  ret i1 %c
+}
+
+; CHECK: @test32
+; X > X + Y -> 0 > Y if there is no overflow.
+; CHECK: ret i1 false
+define i1 @test32(i32 %x, i32 %y) {
+  %rhs = add nuw i32 %x, %y
+  %c = icmp ugt i32 %x, %rhs
+  ret i1 %c
+}
+
+; CHECK: @test33
+; X - Y > X -> 0 > Y if there is no overflow.
+; CHECK: %c = icmp slt i32 %y, 0
+; CHECK: ret i1 %c
+define i1 @test33(i32 %x, i32 %y) {
+  %lhs = sub nsw i32 %x, %y
+  %c = icmp sgt i32 %lhs, %x
+  ret i1 %c
+}
+
+; CHECK: @test34
+; X - Y > X -> 0 > Y if there is no overflow.
+; CHECK: ret i1 false
+define i1 @test34(i32 %x, i32 %y) {
+  %lhs = sub nuw i32 %x, %y
+  %c = icmp ugt i32 %lhs, %x
+  ret i1 %c
+}
+
+; CHECK: @test35
+; X > X - Y -> Y > 0 if there is no overflow.
+; CHECK: %c = icmp sgt i32 %y, 0
+; CHECK: ret i1 %c
+define i1 @test35(i32 %x, i32 %y) {
+  %rhs = sub nsw i32 %x, %y
+  %c = icmp sgt i32 %x, %rhs
+  ret i1 %c
+}
+
+; CHECK: @test36
+; X > X - Y -> Y > 0 if there is no overflow.
+; CHECK: %c = icmp ne i32 %y, 0
+; CHECK: ret i1 %c
+define i1 @test36(i32 %x, i32 %y) {
+  %rhs = sub nuw i32 %x, %y
+  %c = icmp ugt i32 %x, %rhs
+  ret i1 %c
+}
+
+; CHECK: @test37
+; X - Y > X - Z -> Z > Y if there is no overflow.
+; CHECK: %c = icmp sgt i32 %z, %y
+; CHECK: ret i1 %c
+define i1 @test37(i32 %x, i32 %y, i32 %z) {
+  %lhs = sub nsw i32 %x, %y
+  %rhs = sub nsw i32 %x, %z
+  %c = icmp sgt i32 %lhs, %rhs
+  ret i1 %c
+}
+
+; CHECK: @test38
+; X - Y > X - Z -> Z > Y if there is no overflow.
+; CHECK: %c = icmp ugt i32 %z, %y
+; CHECK: ret i1 %c
+define i1 @test38(i32 %x, i32 %y, i32 %z) {
+  %lhs = sub nuw i32 %x, %y
+  %rhs = sub nuw i32 %x, %z
+  %c = icmp ugt i32 %lhs, %rhs
+  ret i1 %c
+}

test/Transforms/InstCombine/sub.ll

@@ -209,7 +209,7 @@ define i1 @test22(i32 %a, i32 %b) zeroext nounwind  {
 	%tmp5 = icmp eq i32 %tmp2, %tmp4	
 	ret i1 %tmp5
 ; CHECK: @test22
-; CHECK: %tmp5 = icmp eq i32 %a, %b
+; CHECK: %tmp5 = icmp eq i32 %b, %a
 ; CHECK: ret i1 %tmp5
 }