[InstCombine] Drop samesign in InstCombine (#112480)

Closes #112476.

Author: dtcxzyw

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -1738,7 +1738,7 @@ Instruction *InstCombinerImpl::foldICmpAndShift(ICmpInst &Cmp,
 
     // Compute X & (C2 << Y).
     Value *NewAnd = Builder.CreateAnd(Shift->getOperand(0), NewShift);
-    return replaceOperand(Cmp, 0, NewAnd);
+    return new ICmpInst(Cmp.getPredicate(), NewAnd, Cmp.getOperand(1));
   }
 
   return nullptr;
@@ -1844,7 +1844,7 @@ Instruction *InstCombinerImpl::foldICmpAndConstConst(ICmpInst &Cmp,
                                                /*HasNUW=*/true),
                              One, Or->getName());
         Value *NewAnd = Builder.CreateAnd(A, NewOr, And->getName());
-        return replaceOperand(Cmp, 0, NewAnd);
+        return new ICmpInst(Cmp.getPredicate(), NewAnd, Cmp.getOperand(1));
       }
     }
   }

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -1448,6 +1448,7 @@ Instruction *InstCombinerImpl::foldSelectEqualityTest(SelectInst &Sel) {
              m_c_SpecificICmp(ICmpInst::ICMP_EQ, m_Specific(X), m_Specific(Y))))
     return nullptr;
 
+  cast<ICmpInst>(XeqY)->setSameSign(false);
   return replaceInstUsesWith(Sel, XeqY);
 }
 

llvm/test/Transforms/InstCombine/icmp-and-shift.ll

@@ -619,6 +619,19 @@ define i1 @test_shr_and_1_ne_0(i32 %a, i32 %b) {
   ret i1 %cmp
 }
 
+define i1 @test_shr_and_1_ne_0_samesign(i32 %a, i32 %b) {
+; CHECK-LABEL: @test_shr_and_1_ne_0_samesign(
+; CHECK-NEXT:    [[TMP1:%.*]] = shl nuw i32 1, [[B:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = and i32 [[A:%.*]], [[TMP1]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[TMP2]], 0
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %shr = lshr i32 %a, %b
+  %and = and i32 %shr, 1
+  %cmp = icmp samesign ne i32 %and, 0
+  ret i1 %cmp
+}
+
 define i1 @test_const_shr_and_1_ne_0(i32 %b) {
 ; CHECK-LABEL: @test_const_shr_and_1_ne_0(
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl nuw i32 1, [[B:%.*]]

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

@@ -33,6 +33,22 @@ entry:
   ret i1 %equal
 }
 
+define i1 @icmp_equality_test_constant_samesign(i42 %X, i42 %Y) {
+; CHECK-LABEL: @icmp_equality_test_constant_samesign(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[XEQY:%.*]] = icmp eq i42 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[XEQY]]
+;
+entry:
+  %XeqC = icmp eq i42 %X, -42
+  %YeqC = icmp eq i42 %Y, -42
+  %XeqY = icmp samesign eq i42 %X, %Y
+  %not.YeqC = xor i1 %YeqC, true
+  %and = select i1 %not.YeqC, i1 %XeqY, i1 false
+  %equal = select i1 %XeqC, i1 %YeqC, i1 %and
+  ret i1 %equal
+}
+
 define i1 @icmp_equality_test_swift_optional_pointers(i64 %X, i64 %Y) {
 ; CHECK-LABEL: @icmp_equality_test_swift_optional_pointers(
 ; CHECK-NEXT:  entry:

llvm/test/Transforms/InstCombine/icmp.ll

@@ -3203,6 +3203,21 @@ define i1 @icmp_and_or_lshr(i32 %x, i32 %y) {
   ret i1 %ret
 }
 
+define i1 @icmp_and_or_lshr_samesign(i32 %x, i32 %y) {
+; CHECK-LABEL: @icmp_and_or_lshr_samesign(
+; CHECK-NEXT:    [[SHF1:%.*]] = shl nuw i32 1, [[Y:%.*]]
+; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[SHF1]], 1
+; CHECK-NEXT:    [[AND3:%.*]] = and i32 [[X:%.*]], [[OR2]]
+; CHECK-NEXT:    [[RET:%.*]] = icmp ne i32 [[AND3]], 0
+; CHECK-NEXT:    ret i1 [[RET]]
+;
+  %shf = lshr i32 %x, %y
+  %or = or i32 %shf, %x
+  %and = and i32 %or, 1
+  %ret = icmp samesign ne i32 %and, 0
+  ret i1 %ret
+}
+
 define <2 x i1> @icmp_and_or_lshr_vec(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @icmp_and_or_lshr_vec(
 ; CHECK-NEXT:    [[SHF:%.*]] = lshr <2 x i32> [[X:%.*]], [[Y:%.*]]