[CodeGenPrepare] Fix signed overflow

Author: mikael-nilsson-arm

llvm/lib/CodeGen/CodeGenPrepare.cpp

@@ -5447,11 +5447,18 @@ bool AddressingModeMatcher::matchAddr(Value *Addr, unsigned Depth) {
       TPT.getRestorationPoint();
   if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) {
     if (CI->getValue().isSignedIntN(64)) {
-      // Fold in immediates if legal for the target.
-      AddrMode.BaseOffs += CI->getSExtValue();
-      if (TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace))
-        return true;
-      AddrMode.BaseOffs -= CI->getSExtValue();
+      // Check if the addition would result in a signed overflow.
+      bool Overflow = false;
+      APInt BaseOffs(64, AddrMode.BaseOffs, true);
+      APInt CIVal(64, CI->getValue().getSExtValue(), true);
+      auto Result = BaseOffs.sadd_ov(CIVal, Overflow);
+      if (!Overflow) {
+        // Fold in immediates if legal for the target.
+        AddrMode.BaseOffs = Result.getSExtValue();
+        if (TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace))
+          return true;
+        AddrMode.BaseOffs -= CI->getSExtValue();
+      }
     }
   } else if (GlobalValue *GV = dyn_cast<GlobalValue>(Addr)) {
     // If this is a global variable, try to fold it into the addressing mode.