[llvm] [ConstraintElimination] Extend unsigned-to-signed fact transfer (PR #66173)

[Nikita Popov via llvm-commits]

================
@@ -228,3 +228,86 @@ then:
 else:
   ret i1 0
 }
+
+define i1 @ule_signed_pos_constant_1(i8 %a, i8 %b) {
+; CHECK-LABEL: @ule_signed_pos_constant_1(
+; CHECK-NEXT:    [[B_NON_NEG:%.*]] = icmp sge i8 [[B:%.*]], 0
+; CHECK-NEXT:    call void @llvm.assume(i1 [[B_NON_NEG]])
+; CHECK-NEXT:    [[A_ULE_B:%.*]] = icmp ule i8 [[A:%.*]], [[B]]
+; CHECK-NEXT:    call void @llvm.assume(i1 [[A_ULE_B]])
+; CHECK-NEXT:    [[RESULT_XOR:%.*]] = xor i1 true, true
+; CHECK-NEXT:    ret i1 [[RESULT_XOR]]
+;
+  %b_non_neg = icmp sge i8 %b, 0
+  call void @llvm.assume(i1 %b_non_neg)
+  %a_ule_b = icmp ule i8 %a, %b
+  call void @llvm.assume(i1 %a_ule_b)
+
+  %sle_test = icmp sle i8 %a, %b
+  %result_xor = xor i1 %sle_test, 1
+
+  ret i1 %result_xor
+}
+
+define i1 @ule_signed_pos_constant_2(i8 %a) {
+; CHECK-LABEL: @ule_signed_pos_constant_2(
+; CHECK-NEXT:    [[A_ULT_4:%.*]] = icmp ule i8 [[A:%.*]], 4
+; CHECK-NEXT:    br i1 [[A_ULT_4]], label [[THEN:%.*]], label [[ELSE:%.*]]
+; CHECK:       then:
+; CHECK-NEXT:    [[RES_1:%.*]] = xor i1 true, true
+; CHECK-NEXT:    [[RES_2:%.*]] = xor i1 [[RES_1]], true
+; CHECK-NEXT:    ret i1 [[RES_2]]
+; CHECK:       else:
+; CHECK-NEXT:    [[C_2:%.*]] = icmp sge i8 [[A]], 0
+; CHECK-NEXT:    [[C_3:%.*]] = icmp sle i8 [[A]], 4
+; CHECK-NEXT:    [[RES_3:%.*]] = xor i1 [[C_2]], [[C_3]]
+; CHECK-NEXT:    [[C_4:%.*]] = icmp sle i8 [[A]], 5
+; CHECK-NEXT:    [[RES_4:%.*]] = xor i1 [[RES_3]], [[C_4]]
+; CHECK-NEXT:    ret i1 [[RES_4]]
+;
+  %a.ult.4 = icmp ule i8 %a, 4
+  br i1 %a.ult.4, label %then, label %else
+
+then:
+  %t.0 = icmp sge i8 %a, 0
+  %t.1 = icmp sle i8 %a, 4
+  %res.1 = xor i1 %t.0, %t.1
+
+  %c.0 = icmp sle i8 %a, 5
+  %res.2 = xor i1 %res.1, %c.0
+  ret i1 %res.2
+
+else:
+  %c.2 = icmp sge i8 %a, 0
+  %c.3 = icmp sle i8 %a, 4
+  %res.3 = xor i1 %c.2, %c.3
+
+  %c.4 = icmp sle i8 %a, 5
+  %res.4 = xor i1 %res.3, %c.4
+
+  ret i1 %res.4
+}
+
+define i1 @uge_assumed_positive_values(i8 %a, i8 %b) {
+; CHECK-LABEL: @uge_assumed_positive_values(
+; CHECK-NEXT:    [[B_NON_NEG:%.*]] = icmp sge i8 [[B:%.*]], 0
+; CHECK-NEXT:    call void @llvm.assume(i1 [[B_NON_NEG]])
+; CHECK-NEXT:    [[A_NON_NEG:%.*]] = icmp sge i8 [[A:%.*]], 0
+; CHECK-NEXT:    call void @llvm.assume(i1 [[A_NON_NEG]])
+; CHECK-NEXT:    [[A_UGT_B:%.*]] = icmp uge i8 [[A]], [[B]]
+; CHECK-NEXT:    call void @llvm.assume(i1 [[A_UGT_B]])
+; CHECK-NEXT:    ret i1 true
+;
+  %b_non_neg = icmp sge i8 %b, 0
+  call void @llvm.assume(i1 %b_non_neg)
+  %a_non_neg = icmp sge i8 %a, 0
+  call void @llvm.assume(i1 %a_non_neg)
----------------
nikic wrote:

Drop one assume?

We should probably also have the ugt variant of this test?

https://github.com/llvm/llvm-project/pull/66173