[CGP] Fix GEP issue with out of range APInt constant values not fitting in int64_t

Test case reduced from https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=7173

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@339556 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CodeGenPrepare.cpp

@@ -3801,8 +3801,13 @@ bool AddressingModeMatcher::matchOperationAddr(User *AddrInst, unsigned Opcode,
       } else {
         uint64_t TypeSize = DL.getTypeAllocSize(GTI.getIndexedType());
         if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) {
-          ConstantOffset += CI->getSExtValue() * TypeSize;
-        } else if (TypeSize) {  // Scales of zero don't do anything.
+          const APInt &CVal = CI->getValue();
+          if (CVal.getMinSignedBits() <= 64) {
+            ConstantOffset += CVal.getSExtValue() * TypeSize;
+            continue;
+          }
+        }
+        if (TypeSize) {  // Scales of zero don't do anything.
           // We only allow one variable index at the moment.
           if (VariableOperand != -1)
             return false;

test/CodeGen/X86/getelementptr.ll

@@ -78,3 +78,14 @@ define i8* @test_sext16(i8* %ptr) nounwind {
   %d = getelementptr i8, i8* %ptr, i8 -21
   ret i8* %d
 }
+
+
+; Test out of int64_t range indices
+
+; OSS-Fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=7173
+define void @test_outofrange(i96* %ptr) nounwind {
+; CHECK-LABEL: test_outofrange
+  %d = getelementptr i96, i96* %ptr, i96 39614081257132168796771975167
+  %ld = load i96, i96* %d, align 1
+  unreachable
+}