[ConstraintElimination] Transfer info from SLT to unsigned system.

If A s< B holds, then A u< also holds, if A s>= 0. https://alive2.llvm.org/ce/z/J4JZuN
llvm · Jun 23, 2022 · 9a33f39 · 9a33f39
1 parent 30e49a3
commit 9a33f39
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Showing 2 changed files with 6 additions and 2 deletions.
diff --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -403,6 +403,10 @@ void ConstraintInfo::transferToOtherSystem(
   switch (Pred) {
   default:
     break;
+  case CmpInst::ICMP_SLT:
+    if (doesHold(CmpInst::ICMP_SGE, A, ConstantInt::get(B->getType(), 0)))
+      addFact(CmpInst::ICMP_ULT, A, B, IsNegated, NumIn, NumOut, DFSInStack);
+    break;
   case CmpInst::ICMP_SGT:
     if (doesHold(CmpInst::ICMP_SGE, B, ConstantInt::get(B->getType(), -1)))
       addFact(CmpInst::ICMP_UGE, A, ConstantInt::get(B->getType(), 0),

diff --git a/llvm/test/Transforms/ConstraintElimination/transfer-signed-facts-to-unsigned.ll b/llvm/test/Transforms/ConstraintElimination/transfer-signed-facts-to-unsigned.ll
@@ -13,7 +13,7 @@ define i1 @len_known_positive_via_idx_1(i8 %len, i8 %idx) {
 ; CHECK-NEXT:    [[T_2:%.*]] = icmp sge i8 [[LEN]], 0
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp sge i8 [[LEN]], 2
 ; CHECK-NEXT:    [[C_2:%.*]] = icmp sge i8 [[LEN]], 2
-; CHECK-NEXT:    [[RES_1:%.*]] = xor i1 [[T_1]], true
+; CHECK-NEXT:    [[RES_1:%.*]] = xor i1 true, true
 ; CHECK-NEXT:    [[RES_2:%.*]] = xor i1 [[RES_1]], [[C_1]]
 ; CHECK-NEXT:    [[RES_3:%.*]] = xor i1 [[RES_2]], [[C_2]]
 ; CHECK-NEXT:    ret i1 [[RES_3]]
@@ -609,7 +609,7 @@ define i1 @slt_first_op_known_pos(i8 %idx) {
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[CMP]])
 ; CHECK-NEXT:    [[T_1:%.*]] = icmp ult i8 2, [[IDX]]
 ; CHECK-NEXT:    [[T_2:%.*]] = icmp ult i8 1, [[IDX]]
-; CHECK-NEXT:    [[RES_1:%.*]] = xor i1 [[T_1]], [[T_2]]
+; CHECK-NEXT:    [[RES_1:%.*]] = xor i1 true, true
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp ult i8 3, [[IDX]]
 ; CHECK-NEXT:    [[RES_2:%.*]] = xor i1 [[RES_1]], [[C_1]]
 ; CHECK-NEXT:    ret i1 [[RES_2]]