Fix eliminateTrunc

Out of loop, an IV user is loop invariant. Using L->isLoopInvariant is
no more valid to distinguish which operand is the loop-constant one from
the IV user.

Author: v01dxyz

llvm/lib/Transforms/Utils/SimplifyIndVar.cpp

@@ -554,7 +554,7 @@ bool SimplifyIndvar::eliminateTrunc(TruncInst *TI) {
   };
   // Replace all comparisons against trunc with comparisons against IV.
   for (auto *ICI : ICmpUsers) {
-    bool IsSwapped = L->isLoopInvariant(ICI->getOperand(0));
+    bool IsSwapped = ICI->getOperand(0) != TI;
     auto *Op1 = IsSwapped ? ICI->getOperand(0) : ICI->getOperand(1);
     IRBuilder<> Builder(ICI);
     Value *Ext = nullptr;

llvm/test/Transforms/IndVarSimplify/out_of_loop_eliminate_truncate.ll

@@ -24,8 +24,7 @@ define dso_local noundef zeroext i1 @matchSimpleRecurrence(
 ; CHECK-NEXT:    [[CMP_NOT17_LCSSA:%.*]] = phi i1 [ [[CMP_NOT17]], %[[FOR_BODY]] ]
 ; CHECK-NEXT:    [[I_016_LCSSA_WIDE:%.*]] = phi i64 [ [[INDVARS_IV]], %[[FOR_BODY]] ]
 ; CHECK-NEXT:    [[DOTLCSSA:%.*]] = phi ptr [ [[TMP0]], %[[FOR_BODY]] ]
-; CHECK-NEXT:    [[ZEXT:%.*]] = zext i32 poison to i64
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i64 [[I_016_LCSSA_WIDE]], [[ZEXT]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i64 [[I_016_LCSSA_WIDE]], 0
 ; CHECK-NEXT:    [[IDXPROM1:%.*]] = zext i1 [[TMP1]] to i64
 ; CHECK-NEXT:    [[ARRAYIDX2:%.*]] = getelementptr inbounds ptr, ptr [[P]], i64 [[IDXPROM1]]
 ; CHECK-NEXT:    [[TMP2:%.*]] = load ptr, ptr [[ARRAYIDX2]], align 8
@@ -99,7 +98,7 @@ define i1 @check_size_str(ptr %str, i32 %str.size, i32 %n) {
 ; CHECK-NEXT:    br i1 [[OR]], label %[[EXIT:.*]], label %[[LOOP]]
 ; CHECK:       [[EXIT]]:
 ; CHECK-NEXT:    [[I_LCSSA:%.*]] = phi i64 [ [[I]], %[[LOOP]] ]
-; CHECK-NEXT:    [[ZEXT:%.*]] = zext i32 poison to i64
+; CHECK-NEXT:    [[ZEXT:%.*]] = zext i32 [[N]] to i64
 ; CHECK-NEXT:    [[TMP0:%.*]] = icmp eq i64 [[I_LCSSA]], [[ZEXT]]
 ; CHECK-NEXT:    ret i1 [[TMP0]]
 ;