Add testcase

Signed-off-by: John Lu <[email protected]>

Author: LU-JOHN

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -14961,14 +14961,14 @@ SDValue DAGCombiner::reduceLoadWidth(SDNode *N) {
     const MDNode *OldRanges = LN0->getRanges();
     const MDNode *NewRanges = nullptr;
     // If LSBs are loaded and the truncated ConstantRange for the OldRanges
-    // metadata is not the full-set for the NewWidth then create a NewRanges
+    // metadata is not the full-set for the new width then create a NewRanges
     // metadata for the truncated load
     if (ShAmt == 0 && OldRanges) {
       ConstantRange CR = getConstantRangeFromMetadata(*OldRanges);
 
-      // FIXME: OldRanges should match the width of the old load, so
-      // CR.getBitWidth() should be wider than the new narrower load.  This
-      // check should be unnecessary.
+      // It is possible for an 8-bit extending load with 8-bit range
+      // metadata to be narrowed to an 8-bit load.  This guard is necessary to
+      // ensure that truncation is strictly smaller.
       if (CR.getBitWidth() > VT.getScalarSizeInBits()) {
         ConstantRange TruncatedCR = CR.truncate(VT.getScalarSizeInBits());
         if (!TruncatedCR.isFullSet()) {
@@ -14979,7 +14979,8 @@ SDValue DAGCombiner::reduceLoadWidth(SDNode *N) {
                   ConstantInt::get(*DAG.getContext(), TruncatedCR.getUpper()))};
           NewRanges = MDNode::get(*DAG.getContext(), Bounds);
         }
-      }
+      } else if (CR.getBitWidth() == VT.getScalarSizeInBits())
+        NewRanges = OldRanges;
     }
     Load = DAG.getLoad(
         VT, DL, LN0->getChain(), NewPtr,

llvm/test/CodeGen/X86/narrow-load-metadata.ll

@@ -0,0 +1,21 @@
+; RUN: llc < %s
+;
+; This test case is reduced from RangeConstraintManager.cpp in a ASan build.
+; It crashes reduceLoadWidth in DAGCombiner.cpp. Preservation of range
+; metdata must ensure that ConstantRange truncation is strictly smaller.
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define ptr @_ZN12_GLOBAL__N_121SymbolicRangeInferrer19VisitBinaryOperatorILN5clang18BinaryOperatorKindE15EEENS2_4ento8RangeSetES5_S5_NS2_8QualTypeE() {
+entry:
+  %0 = load i8, ptr null, align 4, !range !0, !noundef !1
+  %retval.sroa.1.0.insert.ext.i = zext i8 %0 to i64
+  %retval.sroa.1.0.insert.shift.i = shl i64 %retval.sroa.1.0.insert.ext.i, 32
+  %coerce.val.ii = trunc i64 %retval.sroa.1.0.insert.shift.i to i40
+  store i40 %coerce.val.ii, ptr null, align 4
+  ret ptr null
+}
+
+!0 = !{i8 0, i8 2}
+!1 = !{}