[EraVM] Add negative tests for overflow folding optimizations

Those tests are sub-optimal ones with redundant arithmetic operations
which should be optimized out.

PR: #591, Issue: #590.

Author: TerryGuo

llvm/test/CodeGen/EraVM/overflow-neg.ll

@@ -0,0 +1,59 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
+; RUN: llc -O2 < %s | FileCheck %s
+
+target datalayout = "E-p:256:256-i256:256:256-S32-a:256:256"
+target triple = "eravm"
+
+declare { i256, i1 } @llvm.uadd.with.overflow.i256(i256, i256)
+declare void @has_overflow(i256)
+declare void @has_no_overflow(i256)
+
+; TODO: #590 x + y is computed twice which is redundant
+define i256 @add_test_neg_1(i256 %a, i256 %b, i256 %x, i256 %y) {
+; CHECK-LABEL: add_test_neg_1:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    add! r3, r4, r5
+; CHECK-NEXT:    add.lt r1, r0, r2
+; CHECK-NEXT:    add r3, r4, r1
+; CHECK-NEXT:    add r1, r2, r1
+; CHECK-NEXT:    ret
+entry:
+  %res1 = call {i256, i1} @llvm.uadd.with.overflow.i256(i256 %x, i256 %y)
+  %res2 = extractvalue {i256, i1} %res1, 0
+  %overflow = extractvalue {i256, i1} %res1, 1
+  %selected = select i1 %overflow, i256 %a, i256 %b
+  %sum = add i256 %res2, %selected
+  ret i256 %sum
+}
+
+; TODO: #590 x + y is computed twice which is redundant
+define void @add_branch_neg_1(i256 %x, i256 %y) {
+; CHECK-LABEL: add_branch_neg_1:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    add r1, r0, r3
+; CHECK-NEXT:    add r3, r2, r1
+; CHECK-NEXT:    add! r3, r2, r2
+; CHECK-NEXT:    jump.lt @.BB1_2
+; CHECK-NEXT:  ; %bb.1: ; %no_overflow_detected
+; CHECK-NEXT:    near_call r0, @has_no_overflow, @DEFAULT_UNWIND
+; CHECK-NEXT:    ret
+; CHECK-NEXT:  .BB1_2: ; %overflow_detected
+; CHECK-NEXT:    near_call r0, @has_overflow, @DEFAULT_UNWIND
+; CHECK-NEXT:    ret
+entry:
+  %res1 = call {i256, i1} @llvm.uadd.with.overflow.i256(i256 %x, i256 %y)
+  %sum = extractvalue {i256, i1} %res1, 0
+  %overflow = extractvalue {i256, i1} %res1, 1
+  br i1 %overflow, label %overflow_detected, label %no_overflow_detected
+
+overflow_detected:
+  call void @has_overflow(i256 %sum)
+  br label %exit
+
+no_overflow_detected:
+  call void @has_no_overflow(i256 %sum)
+  br label %exit
+
+exit:
+  ret void
+}